DC to DC charger NOT required for big Lithium Battery

I have a 400 AH Lithium battery and wanted to hook it directly to my Sprinter Alternator. I ran some tests and measured the charging currents at different battery levels. Also idled the engine for an hour to see if it would overheat. WARNING: This video is a bit technical.

[@kc5mzd]

Your smoking alternator has the fan that mounts behind the pulley removed. under this condition charging any battery will smoke the alternator. You need to take care not to blow the diode pack when charging li batteries. If the alternator tries to put to much power the BMS can disconnect the battery and blow the diodes in the alternator. Just make sure there will never be a condition that causes the alternator to run without a battery and you should be fine. It looks like your setup has the alternator permanently wired to the starting battery with a switch adding the Li battery when needed. With your setup the alternator will never be disconnected from the starting battery. This will prevent damage to the alternator diodes. Great job!

[@lakesidesecurity3845]

It’s an internal fan type. They don’t have a fan behind the pulley.

[@babuddha]

Appreciate your research into the details of Victron video with the (underpowered) 70A Citroen alternator.

[@stefanmargraf7878]

Yeah, and the smoke wasnt disturbed by the cooling fan of the alternator!! Was made up.

[@normansimonsen1203]

Thank you for producing this video. It explains everything I needed to know.

[@trevortrevortsr2]

My first old rig was Citrone van based had a puny 55a alternator and would have died with that load - In Europe RV tend to be much smaller and are van based - my current 3ton Peugeot boxer rig has a 120a alternator and is apparently the heavy duty option - I prefer the DC to DC charger because then I know my expensive 300ah lithium batteries are being managed with the correct 3 stage profile for lithium - Incidentally the Victron Alternator post was narrated by a guy who's focus was on UK canal narrowboats.

[@rvnmedic2709]

Thanks Ron. I had the same question when I installed 200ah lithium in my 2020 Navion. I purchased a Victron 30amp DC to DC charger. When I went to install it to my surprise, Winnebago had already installed a Mastervolt 40amp gizmo. So with the MV and battery BMS there was no need for the DC to DC charger. Saved $170.00.

[@fc436]

30A with 200ah lithium ..sorry but is ridiculous . if you charge a e bike or other things that absorb 15 o 20 a, you dont charge the battery, I see a lot person with this absurd system. I have a 65A alternator and I charge 35 A with 20A load without problem. non burn, no smoke. and my alternator at idle rpm, dont produce more of 25A, so not overheat

[@gereshomeE]

Greetings Ron from an Englishman 🇬🇧 in Arabia! I am about to buy a similar Winnebago to you and I really appreciate all of your videos! THANK YOU! ☺

[@ontheroadwithron2432]

I guess Sprinters are all over the world. Good luck with yours

[@junkerzn7312]

Setting aside the alternator burn-out question, these are expensive batteries and they can easily last 15+ years with minimal degradation... a very long time. But you have to take care of them and that means charging them to the proper voltage (so the BMS inside the battery can properly balance its internal cells), and floating them properly afterwords (which relieves most of the stress on the battery once it is fully charged). That is the real reason why you want all charging sources for the lithium to be on proper charge controllers. One of many reasons, in fact.

[@ontheroadwithron2432]

I don’t worry that much about lithium batteries. The ones in my Makita power tools have lasted 10 years without any special care. They just sit there at various charge levels and i recharge them when they stop working. Same chemistry as my EG4 battery. Nothing wrong with what you say but Ive found them to need a lot less care that the lead acid batteries that i used to have. Cheers

[@JANtheDane]

Hi Ron: I like your videos, and I partly agree with the conclusions of this particular video. I installed two 100AH Battleborn Li batteries in my Thor Delano (very similar to your RV). I noticed a draw from the alternator of 150A+, which got my attention. Like you, I saw that the Mercedes alternator is 220A rated. I did install the Victron 30A DC-DC, so when driving, I get up to 30A from the alternator and up to 30A additional from my solar panels. I have not regret this expense and time spent installing that DC-DC charger.

[@evelynwalker1998]

So you have 2 charge controllers? You could have tried the KISAE DMT1250 that charges from 5-50A selectable by the user and it takes either from solar or from the engine's generator - up to 50A. It cost $250.

[@JANtheDane]

@@evelynwalker1998 Not as simple as that in an RV. Dimensions, wiring paths, and multiple energy sources are all considerations.

[@jaywildeman3403]

Those dual chargers can only handle 30 volts of solar, so they dont work for a lot of systems

[@OurCamper]

Thanks Ron for this video and doing the research. Like the others, I appreciate your videos and look forward to them. Hope to see you at Quartzsite in January. Maybe by then I'll have switched over to lithium too. At least that is the plan so far. :)

[@ontheroadwithron2432]

My wife loves them.

[@cabracove]

That's a good video. I did put in a DC charger in the van, mostly because its also a solar charge controller as well. With the switch to the solar shut off it fools the charger so I get about 48 amps off the alternator, which is plenty.

[@mikeyipeekyeh]

I made the same decisions 3 years ago, when I swapped out the failing factory installed GR24 FLA batteries, and replaced them with 200Ah of Relion lithiums. NO DC to DC chargers, or any other extra hardware, except I added the Charge Wizard Pendant to my PD9245 converter/charger so I can "kick it up a notch" when the sun isn't shining, and I'm plugged in to shore power. I use the same 3 charging sources that you use. I've got a 2018 Navion 24V, and I have had zero problems with my setup, from day one. Always plenty of overnight off grid power from the Relion RB100-LT batteries, and I've got both the propane solenoid vampire draw, as well as the Norcold DC only fridge, nibbling at my DC power reserves. Thanks for including the "Victron smoking alternator sales pitch" video. I laughed when I first saw it, for the same reasons. They definitely "have a dog in that fight". Safe travels, and keep the videos coming. They're great.

[@ontheroadwithron2432]

Nice. Do you have a diesel genny? My particular BMS does not have enough power to start it without the engine running.

[@uhjyuff2095]

@@ontheroadwithron2432 should of kept a couple golf cart batteries connected in parallel to the lithium pack for generator starts! Lead acid is a pain with the maintenance but still works when you need it the most!

[@TheCunneen]

Great information! Very observant and I found this video after watching the victim one and had the same thoughts ! People that think for themselves and ask questions are a rare breed 😄 Great video 👍

[@ontheroadwithron2432]

Totally agree. I do like watching videos for ideas but need to verify myself.

[@evil17]

Good job Ron, well founded decisions based on good logic, research, tests & checks. I like how you saw through some of the marketing BS that gets thrown at us by the manufacturers & used that to draw ur own conclusions with further analysis. I believe u can actually get Positive pole shunts, but you probly could put a second shunt between battery negative & the chassis if you just wanted an in house/dash solution to be able to check the Current data on the fly from alternator to house battery for reassurance all is well. There are generally always solutions, I guess effort, cash & compromise are the main considerations & inhibitors of any install. Good vid, TFS. Cheers

[@evocati6523]

Just because you don't understand the need for something doesn't make it BS

[@jhregalado1]

Great video. Greetings from Spain

[@wonderingworld119]

Re the Victron video. It was an off shoot of videos made for narrowboaters in the UK. We do tend to use two pretty low powered alternators (70amp) on big diesel tractor/forklift engines. We run them about 1000rpm when charging, and we use no airflow as the engine is buried beneath the floor. Most of us are still using AGM, just because it is so hard to get lithium to charge off our alternators. But slowly we are switching over to DC-DC lithium. Even so it is still a pain as we have two alternators and it took me a while to figure out the solution of fitting a second lead acid battery just to limit the 2nd alternator.

[@ontheroadwithron2432]

That makes sense. A lot of my rv friends have seen the Victron video and believe their Mercedes alternator is going to burn up without a dc-dc charger.

[@lefler39]

Thanks Ron. You have covered this important topic with good examples to make an informed decision. The replacement of the factory lead acid with Lithium batteries have improved my Navion camping experience

[@ontheroadwithron2432]

I just found an issue with my battery. It will not start the diesel generator. Current is too much. Working on a solution

[@lefler39]

@@ontheroadwithron2432 Thank you. I wonder why ONAN has that problem? I have replaced my NAPA with Lithium 12 V 100 AMP (Group 31) and its starts the Onan Propane on my 2018 Navion.

[@bobf.7238]

@@lefler39 Hi Steve, It's not an Onan problem. The Diesel and Propane generators for the View/Navion are specified for 300 Amps cranking current. The battery Ron put in is specified for just 200 Amps discharge current. The EG4 is a great battery at a great price but it's going to take two of them to crank the generator. The upside of this is he'll have twice the capacity for twice the boon docking fun. I'm a bit envious. Like you, I also have two 100 AH Lithium batteries. Mine are the Lion Energy UT1300s from Costco rated for 150 Amps discharge current each. Two of them in parallel are 300 Amps, just perfect for cranking our generators.

[@rosstaylor3927]

Thanks for the video. I have an 2006 Winnebago view. Not sure what you have. But the wiring looks identical I even have the EG4 server rack. I had a lot of people telling me I can’t. I think you did a great job covering all the points they made of why it will fail.

[@ontheroadwithron2432]

Great. Did you go with the 12 volt version? I thought about the 24volt but decided it was more trouble than worth it.

[@rosstaylor3927]

Yeah 12v. I linked into 24 and 48. I read they are “superior” voltages for many applications. But since a the wire runs are relatively short I figured 12v would be fine. Thought about going 24v for solar though. I’m not 100% how that would work. I’m still learning. Some info sticks, some goes in one ear and out the other.

[@ericschweitzer2454]

Hello I have a 2006 Winnebago View as well I'm installing 200 amps of lithium battery and I'm wondering if I need a DC to DC charger for my 150 amp alternator. Did you use one ?

[@SalmonKing52]

Another great video Ron. You have convinced me of one thing for certain. Even though I was a NAVY Electronics instructor (I retired from that over 30 years ago), I am NOT even close to qualified to upgrade my solar (currently I have one 190W panel and 2 12vDC Wet Cell) batteries in my 2022 Jayco Melbourne. Now the question is…when can I bring my coach and checkbook/credit card to you and you can teach me while WE install a comparable system into my unit? Don’t laugh…I’m dead serious! I don’t know enough to know who to trust to do an installation like you have…but I know I want it.

[@ontheroadwithron2432]

Very kind but of course i am retired. Just as busy as when i was working especially with 4 grand daughters. 😊

[@SalmonKing52]

@@ontheroadwithron2432 that makes both of us sir…lol Sometimes I think I need to go back to work just so I can get a break!! 🤣🤣🤣

[@victorjcano]

I UNDERSTAND IT, IT'S NOT THE CURRENT THAT IS THE PROBLEM BUT WHEN THE BMS IN THE LITHUM BATTERY SHUTS DOWN THE CHARGE THE BACK EMF WILL TAKE OUT THE ALTERNATOR DIODES

[@cruze1953]

I was waiting to see if somebody brought this point up. How many even know what back emf is? @@victorjcano

[@MilesAcrossUSA]

Great information Ron.

[@ronaldohrt5109]

Ron, thanks for the information and your videos. I have a 19V and contemplating the lithium upgrade. I have watched so many videos I am getting them all mixed together. While using your alternator to charge lithium are you only doing so at idle? I am curious if there is a bigger draw at highway speeds. Thanks again. Keep up the good fight!

[@ontheroadwithron2432]

No bigger draw driving. The alternator can provide more power with higher rpms according to the specs.

[@koertdubois6781]

Any idea how the “smart” characteristics of our alternators play into this?

[@lkeil84]

Great information Ron. I have a slightly different situation having a boat with 2 diesels, 2 x 140 amp alternators and a 130 amp battery/alternator isolator. Along with this, I have a port battery bank with 3 group 24 Marine starting batteries in series and the starboard side has 4x138 amp Lithium batteries. I have a 60 amp solar charge controller that is typically charging at 30-40 amps to the starboard bank (House) only. There are a couple of things that I have tried. One is to run the watermaker while under way. This uses about 150 amps of 12 volt power while running. This has not been a problem so far. I also have run one of the 16,000 btu air conditioners that takes about 200 amps and have not had a problem either. Unfortunately, I have only had the boat for a short time and do not have amp meters or even proper volt meters installed yet and can only spot check things occasionally. One problem that I do see is that the port side alternator does not contribute as much power as the Starboard alternator. This being due to the isolated voltage sense wires going to each alternator. The port side is the side with a static bank of batteries that really only run the instruments for the engine and stays at 14 volts. The starboard side runs everything else and has the solar and lithium batteries. There is quite a difference when going through the battery isolator. I am also unsure if the isolators rating of 130 amps, but I don't know if that is total or per alternator or battery bank. So far I have taxed them pretty hard and everything is still working fine. I do have the luxury of having 2 alternators, battery isolator switches, solar charging, a 12 kw generator with 50 amp battery chargers and missive amounts of power. Any single failure is only an inconvenience while out cruising. If anybody has any advice for my particular situations, I would love to hear it.

[@ontheroadwithron2432]

That’s quite a system. My main concern would be if the alternators have sufficient cooling. They can be in a closed engine bay and get pretty hot.

[@lkeil84]

@@ontheroadwithron2432 a closed engine bay is different on a yacht. The engine room stays much cooler than under hood of a vehicle. It has plenty of air circulation and no radiator as all engine cooling is done with sea water. It is also much larger in volume.

[@haydenwatson7987]

I have found the same results as Ron on my motorhome, but my boat is a completely different result. The motorhome is safe because given that the LFP is at one end of the coach and the alternator is at the other, the 90' round trip of wire creates enough resistance to limit the current to the battery to less than 70A. On my boat, the batteries are only a few feet away and my 108A alternator will happily send 108A to the pack right up to the point where it goes up in flames. On the boat, I have an external regulator on the alternator and use a reduced field current to limit output to about 60A max. I also have a digital thermostat with the thermistor mounted to the alternator case which shuts off charging any time the temp gets to 200ºF.

[@haydenwatson7987]

@@lkeil84 I have moved the engine room blower so that the hose is at the front of the alternator and pulling heat directly from the fan. I also added a second cool air fan that pulls cool air from below deck and blows it directly onto the rear of the alternator. Without that, the sound insulated engine space stays at +200ºF.

[@haxificality]

One marketing scheme busted! Great job! Thank you for sharing.

[@ontheroadwithron2432]

Thanks. Too much marketing is not how good your product is but to instill fear that something bad will happen if you don’t buy the product.

[@Btween2]

Thanks for sharing this video. I have a semi truck and I have researched for weeks now trying to figure out if I need a DC to DC charger or isolator. I’m having 4 additional lead acid batteries installed in my semi truck to power my AC when I’m parked. Everywhere I research says that I need a DC to DC charger or isolator but the only explanation for this is when I’m using LIPO4 in combination with AGM/STD batteries. I don’t want to fry my alternator. But I keep reading that if I add more batteries of the same type, I could fry my alternator. Wouldn’t the alternator charge the additional batteries the same as the original 4 already installed just that it will take longer to charge? My semi truck has Idle Smart installed to keep my batteries charged while I’m parked. This monitors my batteries, coolant, and engine to keep my truck at optimal operating efficiency. I set the parameters for when and how long my semi truck idles. When my batteries go too low, my truck starts to charge the batteries. Once the batteries are charged, the truck shuts off. I really don’t understand why I need a DC to DC charger or isolator when I’m not using another battery type.

[@ontheroadwithron2432]

I agree with your reasoning. No need for another device that wastes energy and restricts your charging currents. To be 100% confident, you can install an amp meter to see what your charging rate is running. Then if your know your alternator rating you will know how hard you are working it. And yes, adding more batteries will just make the engine run cycles longer. Both on times and off times.

[@rvlifediy]

Thanks for doing the testing. I always wondered why Sprinters had such a high output alternator when the chassis doesn't require much. Some of the older/new diesel pushers only had 160 amp alternators. I know that my xplorer class b only has a 70amp alternator. On the 2020+ Winnebago Views/Navions with lithium option from the factory, Winnebago put in a 40amp charge mate pro paired with a xantrex charging limiter. It only allows 28 amps from the alternator to the battery unfortunately.

[@ontheroadwithron2432]

Winnebago does not take chances. They have to follow the MB rules. Unfortunately 80 amp chargers are very expensive.

[@koertdubois6781]

On the first day we had our 2021 Navion, I swapped out the 40 amp Mastervolt Charge Mate Pro for the 90 amp version. Coincidentally, Winnebago has now revised their BEG and they now say that 80 amps is okay.

[@rvlifediy]

@@koertdubois6781 thanks that is great to know. Have you measured the actual amps you are getting with the 90amp version?

[@koertdubois6781]

With the 90 amp version of the Charge Mate Pro, I’m getting 70-80 amps of charging current.

[@pommypaul9118]

Hi. I'd like to ask if the feasibility of your approach is based on your alternator's "smartness" (inbuilt ability to limit current)? According to all I have read (a lot!) my 280Ah LiFePO4 battery could draw a hell of a lot of current from my "dumb" alternator (160A rating). Over current protection on the BMS is set at 230A. So would setting this to say, 40 amps (or whatever I choose) give the same control your setup applies? Additionally the 40A DC-DC unit I installed last year (working well so far) supposedly provides the "right (selectable) profile" for charging the lithium battery, optimising charging voltage. Is you LiFePO4 battery happy to take whatever voltage the alternator puts out? Thanks for sharing your findings. I am keen to learn more.

[@ontheroadwithron2432]

A couple points. Alternators put out 14.4 volts and this will not hurt a lithium battery. Yours is a bit lower capacity so I would check how much current is actually flowing into the battery when it is less than 50% full. Depending on the size of your wires and how long they are, the current will be limited. How much is hard to tell. If over 80 amps, I would be concerned and not hook then up directly. Changing the BMS to a lower value such as 80 amps might also limit your discharge rate. My BMS is not adjustable so never tried that. Your 40 amp dc to dc unit seems fine and a good approach with your alternator especially since it is a bit lower output.

[@RollinHomies]

Just curious, would this depend more on the allowed current from the continuous duty solenoid and/or how many batteries you have charging? I’d imagine that solenoid is well over 150d. But if you add another lithium to the bank you’d then have the potential of charging at 300ah’s. I know in the Trevato’s the solenoids have to be replaced over time because of heat.

[@ontheroadwithron2432]

My solenoid is rated for 200 amps continuous. I only draw 80 amps or so from alternator to charge the 400 amp/hr battery. The Hersee Cole solenoids are very reliable.

[@Chris-ut6eq]

Good video, thanks for posting!

[@twisttwister8254]

Thanks. Excellent video.

[@peteroffpist1621]

Depends mainly on the chemistry of the battery. LifePo4 no problem to use the alternator I have been doing that for 5 years on my RV.

[@ontheroadwithron2432]

As long as you have a good alternator.

[@jamestreanor182]

This video is genius. Addressed DPF, DCDC charger, and the myths. Thanks!

[@ontheroadwithron2432]

Glad it was helpful! Just trying to break down a complicated issue.

[@victorjcano]

I UNDERSTAND IT, IT'S NOT THE CURRENT THAT IS THE PROBLEM BUT WHEN THE BMS IN THE LITHUM BATTERY SHUTS DOWN THE CHARGE THE BACK EMF WILL TAKE OUT THE ALTERNATOR DIODES

[@fratermus5502]

@@victorjcano the lead starter battery is still in the circuit

[@thegrave2000]

Sounds scary, can you elaborate? Will a VSR like Victron Cyrix-li-ct protect the alternator from such events?

[@fratermus5502]

@@thegrave2000 From BMS shutdown? No. But the lead starter battery remains in the circuit to absorb such events. The problem occurs with dedicated (secondary) alts that have no lead batt. In high-end systems the BMS commmunicates with the external regulator to shut off the field *before* the BMS trips. Also, don't pay much attention to people who type in ALL CAPS.

[@scottcallahan257]

Great video Ron. Been thinking about going from my 6V golf cart batteries to lithium at some point on my 16 G. One question, what was the reason for adding the swtich to allow you to control when the alternator will charge the batteries ? Wny not constant charging as is the case now with my 6V batteries ?

[@ontheroadwithron2432]

Normally the solar charges what i use. If i was always connected to alternator then the engine would charge them first and the free solar would shutoff. The alternator will lower fuel economy.

[@scottcallahan257]

@@ontheroadwithron2432 - ok got it - thanks Ron.

[@michelpaulcote156]

Thanks. Greatly appreciated. I am switching to lithium ( MB LTV Unity TB 2020) and already have the DC to DC charger. It can be set for lithium. Would you keep it or by-pass. ? Please keep the videos coming. You have a great impact.

[@haydenwatson7987]

I found the same on my Tiffen Phaeton. The reason that it works is because there is 90' of wire round trip from the alternator to the battery and back. I have 920Ah installed and per my BMK monitor, I never get more than 70Ah at the batteries even when they are very low at 13.0v. The Start batteries are always at 14.4v which means that the alternator's internal regulator is reducing current output so that it is not running wide open. The coach has the stock 170A internal regulated alternator.

[@ontheroadwithron2432]

Thanks for sharing your experience. You have a big battery bank for sure.

[@haydenwatson7987]

@@ontheroadwithron2432 It is an all-electric coach and I run a bunch of high-powered computers so I am an energy hog.

[@koertdubois6781]

Ron, once again, you are the greatest! I really appreciated the close look at the Victron video, which many take as gospel. And Mercedes’s BEG have certainly caused some confusion among owners who are doing their own work. But I’m wondering why you were only able to pull 65 amps in your test. Most lithium batteries will draw at least 1C (e.g. at a low state of charge a 100Ah battery will charge at 100 amps, that number declining as the battery gets charged) and I’m thinking that I’d like to see what happens when lithium batteries are capable of pulling several hundred amps.

[@ontheroadwithron2432]

Not sure why. Could be voltage drop in cables or alternator is limiting the charge current.

[@koertdubois6781]

Some actually do use lighter cables as a de facto current limiter. But, the thinner cables throttle the current by increasing resistance, and that means heat, and that means a potential for heat-related problems like fires. I’m still wondering what affect it has to leave the other batteries connected to the charging system, alongside the lithium battery. It’d be simple enough to test, by measuring the current with and without the original batteries connected.

[@evelynwalker1998]

@@ontheroadwithron2432 It could be due to the smaller voltage difference between your alternator and house batteries which at 13.00V look full to the alternator that is tuned to charge Lead Acid/AGM start batteries. I have a SOK 206Ah and its BMS has a charging current protection cutoff at 70A anyway which is conservative and might not be that low on your LiFePO4 batteries. I went with the DMT1250 and for $250 you charge from either sources (but not simultaneously) at a selectable 5-50A. I also have a switch to bridge the 2 batteries because my start battery helps my house batt. with the refrigerator's 1200W initial draw.

[@haydenwatson7987]

@@koertdubois6781 It is the resistance of the wire that is limiting the current but that does not necessarily mean it is a problem. On my coach I get 70A max to the battery when the LFP is very low at 13.0v. The start battery is getting the full 14.4v so there is a 1.4v drop. the power equation is P = volts times amps so 1.4v x 70A = 98W of waste heat. That 98w is over the total run of wire which is 90' on my coach. I doubt that NASA could measure the heat gain in that wire.

[@koertdubois6781]

@@haydenwatson7987 it isn't usually a problem, but the fear is that an unregulated alternator and a large bank of lithium batteries could exceed the safe limits of both the alternator and the cables. I strongly agree that this is rarely a problem, but that doesn't mean it should be ignored.

[@kristiangronberg3150]

The current limiting is actually more the cable resistance, 12.3 vs 14v gives you a voltage drop off 1.7v and when the current is 70A your resistance is 0.024 ohm. In case you have thiger wires or shorter run to the battery, the resistance goes down and the amps goes up. The alternator don't like to run that hot, and you might damage it in the long run. The diodes inside might take damage. I personally killed one alternator diode bridge. How to overcome this is to just rew up the engine, so basically I would tell you to start charging just when you start driving to keep more airflow over the alternator, there is also a fan inside the alternator for cooling, this means the faster you spinn that thing, the more cooling it gets. Other thing is, can we trust that 70A is the max your getting from the alternator? Did you rew engine up or did you just measure while idling? The alternator might need some more rews to give out more, so you might still drow more correct from it.

[@ontheroadwithron2432]

I have seen up to 84 amps for a short time. After 10 minutes or so it drops down to around 70 amps even while driving down the road. Mercedes says alternator can provide 80 amps for coach usage. Other alternators may not be as good.

[@DIY12-24v]

BMS cannot and will not limit charging. BMS is basically a fancy self resetting fuse not a charger at all. Victron does run a BMS they just run an external BMS not internal. There BMS if setup in the Victron eco system can control all parts of the system from turning loads of if battery is getting low can turn chargers on and change there output to suit the needs of the battery and system. Alternator no matter if it's size have a regulator this will prevent it from over heating and burning out, as well as limit its max output so no battery could ever over heat a alternator that's younger then 40 off years. I would say rpm was too low or some how increase discharge by using a dcdc charger of some sort to keep the alternator charging when it decreases it's voltage to decrease it's output. Alternator charging will work it's not the alternator that's the issue it's the battery. Using alternator will shorten the life of your batteries as it will hold the batteries at charging voltage. So if you don't ever fully charged the battery with alternator this should not be much of an issue. Next issue is charging speed and is why people use dcdc charger. As the lithium battery voltage increases the voltage difference decreases so this will decrease charging speed so under 80% it should charge fast over 80% it will start slowing down fast. Where a dcdc charger will charge lithium at max amp rating though the full charging cycle.

[@MacRobbSimpson]

I've been playing with a relatively cheap Daly 'smart' BMS, and I would disagree with alternator charging reducing the life. What I see is that you can charge your lifepo4 bank from a 14+v source, and what will happen is that the cells will charge(at fairly high current) until they get full. Then, the voltage rises pretty quickly, and the BMS cuts out the charging mosfets until the voltage drops below the setpoint. In the case of my BMS, I can set that voltage. Others are just a default 3.65v/cell. If the alternator puts out 14.6V, lets say, once the battery is full the BMS will disconnect it and won't damage the battery... but the alternator may not be happy, unless you have a separate load / battery to keep it under control. And yes, I agree that a BMS will not limit charging to a given amp range, they will just cut it out completely if it gets overloaded. The actual amp draw will be based on the wiring and other resistances. However, I have also seen a BMS with actual current limiting out there - you can tell by the large inductor. These will use PWM to limit the current to the given value.

[@DIY12-24v]

@@MacRobbSimpson that's completely wrong. The only reason for a BMS to stop charging is the battery is in fault. What happened in the real world is alternator voltage will hold the battery at 13.8-14.6v depending on alternator. The battery will site at this voltage until the vehicle stops. This will and does decrease battery life as lithium does not like being held at charging voltage. Just look at all the issues DCS lithium is having

[@MacRobbSimpson]

@@DIY12-24v kzbin.info/www/bejne/bZzcZp6JbKd8pbc I just did this test and recorded it

[@DIY12-24v]

@@MacRobbSimpson wow you are going to kill your car with the battery going in to self protection like that with the alternator still going. the bms is no controlling the charging all its doing it going in to self protection mode because of your setup is not suited to the battery. you need to get yourself a starting battery bms not a deep cycle bms

[@ramhammer10-4]

Great Job Ron...

[@KU9L]

Great video Ron. I bought a 20-amp DC-DC converter for my Lance travel trailer, but have not installed it yet. Ford's 10-ga wire is notorious for giving a dismal charge through the 7-pin trailer plug at the rear of the truck. Lance usually installs a special plug for their truck campers with an upgraded 8-ga wire, but that only gives a bit extra in my past testing. With our travel trailer, I was only charging at about 2-amps during normal highway speeds on level ground and it would climb to 20-amps on steep grade climbs with the truck downshifted so the tachometer is registering 4,000 RPMs which gives the 220-amp alternator some extra spinning power. The truck wants to be at 13.7 volts and it cannot tell that my LIFEPO4 batteries are at 50%, etc. I temporarily attached a 6-ga wire with an Anderson connecter and I get 20-amps continuously on level grade from my DC-DC controller. I have not installed it permanently yet because I do not like having the extra heavy wires between the truck and travel trailer, not as convenient as a motorhome or even a 5W trailer. Perhaps this is my cue to finally upgrade to a motorhome if I can find one that isn't overpriced 50% more than it is worth these days. Thanks again Ron, keep up the inspiration sir!

[@ontheroadwithron2432]

Hang in there. What goes up will come down. Motorhomes are a good all in one solution but are more expensive to maintain. Key is to wait until you find something that meets your needs.

[@ramhammer10-4]

They're coming down in price

[@johnlove4183]

Nicely done. If you shut that switch off while the alternator is pushing a lot of amps out (to the lithium bank) will it harm the alternator? The external regulators seem to be designed to prevent this. As someone who burned up an alternator when I flipped a battery switch on my boat I'm sensitive to that situation.

[@ontheroadwithron2432]

Good question. That is one of the reasons that I keep the AGM starting battery. It works as a sink for any voltage spikes.

[@user-mt3cf3hs7f]

Ron, found your channel. You're inspiring me with the Tesla and the Solar. How much have you sunk into the Sprinter camper since you bought it? seems like a money pit. Have you calculated the cost?

[@ontheroadwithron2432]

Good question. I haven’t added it up but most mods are pretty inexpensive since my time is free. I feel that the mods keep my unit up to date for a fraction of the cost of a new unit. Only this i miss is the adaptive cruise control that’d be nice.

[@bobf.7238]

I have two Lion Energy 100 AH lithium batteries in my Navion 24D with the same alternator as Grandpa Ron. My Daughter has two Battle Born 100 AH lithium batteries in her trailer. These batteries all have battery management systems (BMS). The Lion Energy max charging specification per battery is 100 Amps, the Battle Born are rated at 50 Amps each. I think this is a maximum charge rate so the batteries don't over heat, and may not be a limit set by the BMS. If the BMS did limit to these amounts, you could never charge depleted batteries directly from the alternator as the BMS would immediately disconnect at every attempt. You would have to charge them by hooking up to an alternate, current limited source. The total charge rate of two depleted Lion batteries might be as much as 200 Amps or more and 100 Amps for the two Battle Borns. Plenty of draw to burn out the Navion alternator and possibly my daughter's smaller tow vehicle alternator. We both use a DC to DC charger to limit the current just in case the batteries are ever depleted. We don't want to have to go to all the trouble to carry and have to jump charge our batteries from some current limited alternate source or take the chance that we could burn out the alternator. PLEASE BE CAREFUL!

[@ontheroadwithron2432]

You should measure the actual current. With tge long cable runs and the smart alternator, i dont think you could ever get that much charging. Of course if you are running AC or a heater in addition then still best to measure it to know. My BMS can use 200 amps also but I’m only getting 75 amps charging.

[@bobf.7238]

​@@ontheroadwithron2432 Hi Ron, thanks for the response. I really enjoy your channel and your granddaughter is the cutest. I agree that knowing the current draw would be useful information. However, batteries don't charge linearly but rather draw the most when they are discharged. I'd first have to completely discharge the batteries for that measurement to be meaningful. Then, that measurement would only apply to my two batteries and wouldn't be useful for anybody else reading here. Also, the test might be limited by the alternator maximum or fuses in the line, so I'd need to use a separate high current source which is expensive. Otherwise, the maximum battery draw potential might never be reached during the measurement. For me, it would much easier to maintain peace of mind by spending $216 on a Renogy 60 Amp DC to DC charger versus risking a potential break down and expensive repair. I agree that wiring may limit current but blowing fuses is also quite possible. A blown fuse, of course, might protect the alternator but you would never get much of a charge, if any. I don't know what the fuse in the Navion charging circuit is, but the wire in mine is #6 so it's probably fused at 50 to 100 Amps, depending on the wire length. I put a $97, twenty-Amp Renogy charger in my daughters rig as the charging wire is #12 and includes a 30 Amp resettable breaker. Without the current limiting DC to DC charger, the breaker would just cycle open and closed over and over again and little or no charging would ever take place. I spent a bit more for my Navion charger. I'm using a Victron 30 Amp as it's more compact and fits nicely under the passenger seat. All the wires necessary to hook it up are there. You simply wire it in parallel with the relay that's used to put the chassis and house batteries together when the engine is running. Remove the relay's sense wire and use it to start the charger. A new button can be added on the seat base to operate the relay for emergency start as the dash button will no longer work for that. Between that 30 Amp charger and the 200 Watts of solar, I've never arrived at a camp site with less than 100% in the batteries.

[@stefanmargraf7878]

Thank you very much! Should have seen your video earlier. Did pay for the victron thing. One thing i didnt get (I am a german), the voltage should be up to 14V, newer cars do that only if DPF regeneration kicks in. Did you put the diode to get a higher voltage constantly?

[@ontheroadwithron2432]

I added the diodes to the Trik-L charger that uses the coach battery to maintain a trickle charge to the chassis battery. Reason is the lithium is 13.7 volts and that needs to be dropped down to match the chassis AGM battery which is 12.7 volts. Otherwise the chassis battery could slowly drain the lithium down to 12.7 volts. Seems to be working well.

[@garydietz8807]

We never boondock, so am I correct in thinking that our converter will keep the lithium batteries near 100% while we are on 30 amp shore power? I use 2 trucks pulling the Trailer so I do not want to use a DC-DC charger unless required.

[@ontheroadwithron2432]

Yes your converter will charge lithium batteries just fine. You do want one designed for lithium or has a lithium settings as the charges voltages are a little different than lead acid batteries.

[@stevensmith8923]

Nice work.👍🏼

[@letsgetcraftinwithsupreetk669]

Hi Ron great information I have a question I have set up where I will get variable rpm from my alternater that can be 100 to 2000 can I charge lead acid battery is and from lead acid battery to lethium batteries or can I charge directly lethium batteries please help me I m serious concern for this

[@ontheroadwithron2432]

Hard to answer without all the facts such as the capacity of both the alternator and lithium battery. Lithium will pull a lot of power from alt. You can test it of course. If you have a 200 amp alternator then keep the Charging current under 100 amps. When driving the alt gets good cooling but be careful when just idling. Might overheat.

[@williamvaughan1218]

Computer controlled alternators nowdays have the capacity to limit current and in fact do. They have incorporated hall effect sensors on the battery cables so it's just a matter modifying the control algorithm.

[@victorjcano]

AS I UNDERSTAND IT, IT'S NOT THE CURRENT THAT IS THE PROBLEM BUT WHEN THE BMS IN THE LITHUM BATTERY SHUTS DOWN THE CHARGE THE BACK EMF WILL TAKE OUT THE ALTERNATOR DIODES. THE DC TO DC UNIT PROTECTS THE ALTERNATOR

[@williamvaughan1218]

@@victorjcano that should only occur if there is a malfunction in normal operation charge voltage should not exceed 14.7v unless the ambient temperature is extremely low then compensated voltages could be as high as 15 volts. A simple capacitor would resolve any voltage spike issues.

[@solarmarinepower]

Hi let me ask you if you have issue about your alternator when Lifepo4 battery bms triggers HvCutoff when it is fully charged with the alternator?

[@ontheroadwithron2432]

I have not had an issue. Of course i do not normally charge lithium with alternator. But when i do use the alternator, i cut it off with my switch which is probably the same as BMS turning it off.

[@bentheguru4986]

The guide for Lithium and Alternators: Smart Alternators (and vehicle ECU controlling it) can be use direct in many cases as they will limit themselves when there is insufficient airflow or RPM. Older self-regulating alternators rarely have thermal protection and will produce max output for the given RPM and usually buildup heat till magic smoke leaks out because they can't spin fast enough to pull cooling airflow. Most batteries DON'T allow you to set the current flow settings on their BMS so many will rely on DC-DC current limitings of an external charger.

[@ontheroadwithron2432]

As always, your particular installation is more important than general rule of thumbs.

[@funkybeef1]

What size wire is connected between your alternator and house batteries and what is the length? It looks like you have the magic setup to limit 80 amps charging and would like to replicate something similar to that with my setup.

[@ontheroadwithron2432]

Most of the wire is original. I believe its 2 ga. I also added a 4’ piece of2/0 welding cable to the new battery.

[@SuperSushidog]

I only have a 95a alternator in my 36ft Class A motorhome with a Ford v-10 engine, so I added a 20A battery to battery charger, as my 560ah lithium battery with a 350a BMS could indeed draw too much current and toast my alternator. It depends entirely on your set-up.

[@ontheroadwithron2432]

Yes it can vary. Mercedes is now allowing 80 amps for charging but then again it is a 220 amp alternator.

[@user-ej1yi9up6f]

7:47 Ron, I’ve got a 2023 Winnebago Navion and want to drop in two renogy 100 ah. Do I really need to change the charger controller or anything else?

[@ontheroadwithron2432]

I believe the newer units are designed for lithium batteries. Just check the solar controller settings for the lithium setting.

[@wolfeb99]

Morton’s on The Move wired their truck camper directly without a dc-dc charger and had horrible overheating issues with their truck alternator. He attributed it to the large wire he used that allowed too much current to flow. The motorhome could well be fine but it is likely more fraught with a trailer or camper.

[@ontheroadwithron2432]

Depends on their alternator size and cables for sure. Some truck alternators are not sized for external loads.

[@fratermus5502]

They ran massive POS/NEG wires and counted on the 2nd alternator sharing the load (it doesn't on his truck).

[@chrisr819]

A FLA alternator does easily 15V, even higher. Done car stereo competition for over 20years and been european champion, so i know a bit of

[@LilyWasHereMB]

have had my sprinter 3 years and just last week I learned that through my Victron app, I can reverse the flow on my DC to DC charger. In other words, I when the Mercedes Me app sends me a message that my battery needs charging, I don't have to drive the van for 30 minutes or more. I can use my house batteries to trickle charge my chassis batteries and do that preemptively to avoid the whole problem.

[@ontheroadwithron2432]

Much better for the engine also.

[@timmorgan4551]

How do you reverse the flow and what is the amp charging rate? Thanks

[@davethewanderer4520]

Could I ask how big is your coach battery bank in AH ? I am having a 400AH bank, I wonder what the current draw would be.

[@ontheroadwithron2432]

It is 400 amp hrs. My alternator charges at 80 amps to battery.

[@CampPrevost]

Great video - you do a great job with all your edits! I just recently went through the same upgrade with the EG4 on my coach. I did find the Wakespeed WS500 alternator regulator to control my alternator and also a Sterling alternator protection device to protect the alternator should the EG4 BMS shut itself off. Appears the Mercedes alternator is pretty smart - doing what the WS500 does for my dinosaur alternator - good find! I was going to mention I run my EG4’s up to 27.5 (13.75) and then float at 26.7. Watching Andy’s off grid garage - and watching the charging myself - appears the lifepo4 charges to about 98-100 at that voltage. The thought not pushing all the way up to 28.8 (14.4) is really not necessary and may extend its life. Just thought I’d mention that and say thanks for the great videos. (I also have a small channel Camp Prevost if you wanted to see my mess! Lol). Aaron.

[@ontheroadwithron2432]

I agree that it is not necessary to keep battery fully charged. My meager 275 watts of solar shuts off at 13.3 volts which is pretty low but fine for my needs.

[@Cabernet2000]

Rob, Why the EG4 and not a sealed lithium battery. Is that better?

[@1sheinz]

I've the same battery size and was hooked to the alternator for the first year. All was well UNTIL I did a longer drive (about 3hrs) after the 3rd replacement I now have a DC-DC Charger. And yes my alternator was a 140amp. Your system will work BUT YOU NEED A TEMPERATURE sensor on the alternator to cut it off from the house bank before it smokes. Because it will, lithium has such a low resistance to current flow it will draw every amp the alternator can produce and while they say they are 140 or 200 they are only rated at that for maybe 1/2-1 hr not continuous for hrs on hrs . It will overheat ar some point and a temp sensor on the relay wire is cheap ($15) insurance to protect a $200-1000 alternator. Edit.. also newer 2000 plus alternators DONOT charge at a High enough voltage to fully charge your lithium house bank. The benefits of a dc-dc charger, while slower it does actually increase the alternator voltage up to 14.6 volts from a usual 13.2V which with lithium is only about 70% if capacity. ;)

[@ontheroadwithron2432]

Your case sounds different. Mercedes allows 80 amps from their alternator for “outfitter usage”. That is approximately what I read for charging current. So I am within the mfg recommendation. Their alternator’s rated at 220 amps.

[@joeoloughlin409]

Also were the tests and figures you refer to under bonnet temps or done in the air con lab ??

[@ontheroadwithron2432]

I did all my testing with the RV parked at my house. The air temperature here in San Diego in the summer is around 70 degrees F.

[@Studmn]

When you turned on the Alternator charging, what was your Voltage at your batteries after charging and during?

[@ontheroadwithron2432]

I tried a couple different battery levels. First was mostly full and the second timeless than half full. Charging rate did not differ as much as I expected. All in the 60 to 70 amp range.

[@jagobouffler6206]

Can you wire a second alternator straight through a dc-dc charger to your leisure’s? Not starter battery in the mix

[@ontheroadwithron2432]

It is better to have a lead acid connected when charging with an alternator. That is because when fully charged the lithium BMS will switch off the charging and it can cause a voltage spike. Lead acid batteries will help adsorb this so it protects the alternator. You can have 2 alternators ok.

[@derrickrees1913]

Good video!! Thank you!

[@gordonhood5902]

I want to buy a 100 ah lithium iron phosphate batter to put in my trunk of my crown vic to run a 500 watt sine wave invertor to charge my laptop, i recently upgraded my alternator to unknown rock auto brand 190 amp this setup has destroyed a 30 ah agm battery from mighty max. Idle charging is cold is 14.1 to 14.4 and idle hot i mean couple hours of running later 13.5v and these numbers are consistent with or without the agm battery connected. Question is for you and i will not hold you responsible for anything going wrong lol but will it be safe running in the trunk off 18 foot 4 gauge power wire and a 1 foot ground, the 18 foot power wire going to the lead acid starting battery in the engine bay? Is there anything i should change like go direct to the alternator or put a amp limiter aka dc to dc charger in line? Thanks for your video and your time!

[@ontheroadwithron2432]

Main issue with 2 different voltage batteries connected is they will settle at the same voltage. The lithium battery will keep feeding the lower voltage chassis battery until it is mostly discharged at 12.8 volts. The alternator will charge both batteries but i’d either put in a disconnect or dc to dc charger to keep them separate unless actively charging them.

[@gordonhood5902]

@@ontheroadwithron2432 Thanks for that much appreciated!

[@wkrp10splayer19]

i have the vic dc2dc charger (40A). when alternator engages, victron ramps amps up slowly to the lithium batteries. when alternator stops [like turn off engine], victron ramps amps down slowly to zero. it must do that for a reason. does your setup do that? i wud love to ditch that vic to get full rated amps into my 12v system. but worried that the vic is doing something important - even tho i don't really know what it is. do you have any updates with your experience after 1 year?

[@ontheroadwithron2432]

I don’t know how the Vic works. My alternator controls the turn on speed. I think it it within a second or two. After a year I’m happy. I normally have the alternator charging switched off and let my solar slowly recharge the batteries. That doesn’t use engine power or fuel. This week we were camping for 3 days and battery used about 25% each day. It’s not too sunny this time of year so solar couldn’t keep up. Now that I’m home, the solar will recharge everything in about a week. I did connect alternator charging for a few minutes. It was 71 amps so all is working fine.

[@wkrp10splayer19]

my vic's slow ramping up/down takes about 30 seconds. i like your setup with your switch - you are the intelligence. the switch is like the command "scotty give me everything she's got"

[@AZRockRunner]

Interesting. I will have two 460Ah LFP banks in parallel, so each can suck up a lot of current. My alternator will be an aftermarket 200A, not sure it has temperature limiter, perhaps not. I will try without the DC-DC first, then decide from there. The 40A Renogy DC-DC is not too expensive. It could be a good protection for the alternator because I want to minimize any engine repair once I hit 70.

[@ontheroadwithron2432]

A lot depends on the particular installation. Voltage drops in cables and any temperature issues. You have a very large battery bank. 40 amp charger is definitely safe but is it adequate for your needs? To fully charge your batteries at 40 amps it would taje 24 hours of constant charging. It you also were using power from the batteries, they would never fully recharge. So the limit of 40 amps may work but it also may be very limiting depending on how fast you want to recharge.

[@AZRockRunner]

@@ontheroadwithron2432 my 800W solar is the primary source.

[@badactor3440]

​@@ontheroadwithron243214 hours, not 24

[@dan32one44]

Good stuff 👍

[@andrerabbani]

Hi, thanks for the video. I'm about to change my AGM batteries with lithium in my Sprinter van. This video is about a year old and I'm asking, after a year, still no dc to dc and no problem with the alternator? Thanks.

[@ontheroadwithron2432]

No issues. Currently drive across country. Have charged with alternator for 2-3 hours at a time. Never started the genny for the last 23 days on the road. Campgrounds and solar do 80% of the charging.

[@andrerabbani]

@@ontheroadwithron2432 Awesome. Thank you. I hope that I can find the correct yellow wire. 😃

[@sveinjohansen6271]

Just watched this. I knew already about this just drop the voltage to get it to lithium range. But. What happens to alternator when bms shuts down either too cold or full ? The force is being put back into alternator when battery stops taking charge ?

[@fratermus5502]

the lead starter battery is still in the circuit. And there is no rule saying we have to overcharge so hard the BMS shuts down charging.

[@ontheroadwithron2432]

Good question. In my case I turn off the alternator charging before it is full and the bms shuts off. The solar panels can finish up the charging. But also, the chassis battery is always connected to the alternator so any high voltage will be dissipated into that lead acid battery. Should be the same as turning off any high power DC device. An occiloscope would be able to measure it.

[@sveinjohansen6271]

@@ontheroadwithron2432 yeah I guess as the lead acid battery is needed to be in circuit to consume the voltage spike when the charging is turned off. DC-DC chargers have coils right to consume some of that voltage spike when charging is finished. Also chargers shut off the current before the battery bms turns off without notice if you set the voltage limit correctly, or charger can talk to bms.

[@richj11]

Great video Ron. I've been running two Lion Energy UT1300 batteries in my View 19D for 28 months now. I did plenty of research and opted to NOT install a DC-DC charger or a BIM. Never an issue and I still stand behind MY decision.

[@victorjcano]

AS I UNDERSTAND IT, IT'S NOT THE CURRENT THAT IS THE PROBLEM BUT WHEN THE BMS IN THE LITHUM BATTERY SHUTS DOWN THE CHARGE THE BACK EMF WILL TAKE OUT THE ALTERNATOR DIODES. THE DC TO DC UNIT PROTECTS THE ALTERNATOR

[@williamvaughan1218]

I use 4 headway lifpo4 cells in my mower. The mower has a constant voltage regulator and so far it has performed excellent. I'm no longer buying crappy overpriced lead acid batteries.

[@jianshe5674]

@@victorjcano As long as you have a lead-acid battery as starting battery, the alternator well never have an occasion to experience no load situation. Since most of the RV still equipped with starting battery and a house battery set, the alternator will never get damaged if the house LiFePO4 is shut down. There are also plenty of power draw from the alternator by various of devices in the engine bay. it is said that there is about 30 to 50 amp of current draw when the engine is on idling.

[@haydenwatson7987]

@@victorjcano Not a problem on my system. The coach start battery is always connected to the alternator so even if both LFP's shut down, there is still the two Group 31 start batteries to dump the current to which eliminates any voltage spike.

[@OskarHartmannsson]

not when you have the led battery from the car charging at the same time @@victorjcano

[@ChocolateManInThailand]

Hmmm... some pretty fair points in this video.

[@SheikhN-bible-syndrome]

The concern isn't with these type of RV batteries but with the car audio style batteries made from cells taken from hybrid vehicles these custom battery packs have an extremely low resistance much lower than you would find in these RV batteries

[@april7_]

It would be interested to see current after starting and rpm between 2000-3000, like driving conditions when it pushes that 200+ Amp out. That 70A is a good value for idle speed indeed!

[@ontheroadwithron2432]

I don’t think it would change much. The alternator supplies 14.4 volts. The amount of current flow will depend on your battery’s voltage and resistance of your cables. My idle voltage it already at 14.4 volts.

[@evil17]

@@ontheroadwithron2432maybe, but if ur cable size & resistance allows more current flow & there are no other restrictions in the circuit, alternator throttling, BMS, etc , it would stand to reason that more revs = more current.

[@badactor3440]

​@@ontheroadwithron2432I don't see any difference in output, whether at idle or at high RPMs.

[@ontheroadwithron2432]

@@badactor3440 Yes, Mine stays about the same also.

[@haydenwatson7987]

I have found the same 70A max when going down the road. I have a BMK monitor on the house bank that shows me the amps delivered to the battery. As Ron said, as long as you are getting 14.4v to the start battery, the alternator is putting out limited current and should not overheat. It is caused by the 90' of wire run from the engine to battery and back. I have 920Ah installed and it is not a problem for me. On a gasser, with the battery right next to the engine the results would likely be different.

[@897aa33]

If you have smart alternator you would need some dc to dc for constant charging? My smart alternator voltage go up and down and summer time stays around 13.3v

[@ontheroadwithron2432]

I believe my alternator puts out 14.4 volts but is close to 13.5 measured at the battery when charging.

[@897aa33]

@ontheroadwithron2432 That's what I mean for modern vehicles you have to imrpovise something otherwise it won't charge efficient. Hence, renogy and victron dc to dc come to play. When I had an older vehicle, I had a split charger like a solenoid that acts like a switch when voltage goes above 14v.

[@vroor32]

What's up Grandpa! 👋 .... So what you are saying is my big semi's diesel Detroit 12.7L alternator can work just fine in direct charge effort? 🤔 ... I've been wanting to get a big lithium battery, so I can just save my $$ and put it towards a 400AH battery

[@ontheroadwithron2432]

Your alternator must be rated for more current than your Lithium battery BMS. If so then yes.

[@vroor32]

@@ontheroadwithron2432 I checked my Alternator. It's rated @ 145A .... I'm seeing 14.4V on startup (900rpm high idle) then settles to 13.9V .... When running at 60mph I'm seeing 14.3-14.4V on radio display and also on PZEM-015 Battery monitor. So I suppose this should be able to recharge a 300AH or 400AH lithium pretty quick?

[@ontheroadwithron2432]

@@vroor32 A lot depends on the size and length of the cable from the alternator to the batteries. Sprinter alternator is 220 amps, so yours is a bit lower. Try to get an amp meter of battery monitor to see how much charging current you are actually getting. Try to keep it under 80 amps to have a safe margin.

[@vroor32]

@@ontheroadwithron2432 good to know. I went with 4/0ga pure copper for 15 feet to my 2K inverter. Maybe I will re-route that cable from Alternator to Lithium battery once this all becomes clearer. I'm planning to get a clamp meter as I solve this puzzle.

[@chrisr819]

Very simple answer: if the alternator has a build in temp control, which the 150-240AH in the Mercedes have you can hook the alternator directly to the alternator. BUT the lead regulator while throw up to 15V at the end of the charge and overcharge the lithium. The BMS will protect the battery but only when that 15V voltage is there for some time and will damage over time. You need to install a relay that cuts of the alternator when voltage is at 14.2-14.6V depending on the specs of your lithium.

[@ontheroadwithron2432]

I have never personally seen 15 volts from alternator. Are referring to when all batteries are fully charged?

[@chrisr819]

I refer to when the FLA is fully charged you see up to 15.8V and with AGM setting (which most smart alternator have today) up to 15V. So you have to be careful and disconnect the Lithium earlier. You may never see when cable is underdimensioned and your voltage drop on the cable is 0.5V, the argodiode splittingbdiode used with 0.5V voltage drop or connection is slightly corroded which unintentionally saved thousands of drop in lithium from being overcharged and damaged...and then claim this is all marketing scam you have to modify alternator or take other measures but simply insufficient install saved their ass...

[@gregorybolin4672]

How do u charge a 48v battery with 14volts ? Is there a 12v hook up on the battery ?

[@ontheroadwithron2432]

I have the 12 volt battery model. If i were to go to 48volts, would need an additional 48 volt alternator.

[@abcd-by6rw]

Love this - not buying into the BS and sticking to your instinct!

[@ontheroadwithron2432]

Thanks. I like to test everything.

[@victorjcano]

AS I UNDERSTAND IT, IT'S NOT THE CURRENT THAT IS THE PROBLEM BUT WHEN THE BMS IN THE LITHUM BATTERY SHUTS DOWN THE CHARGE THE BACK EMF WILL TAKE OUT THE ALTERNATOR DIODES

[@abcd-by6rw]

@@victorjcano ​ @Victor J. Cano Interesting - thanks for sharing. Where is this back EMF being produced? The battery itself is not an inductive load. Had the alternator been directly powering an inverter then this may cause an issue. High power diodes are available (200A) for relatively cheap (~£25), they could mitigate any back EMF, I think.

[@victorjcano]

@@abcd-by6rw i know through personal experience if you’re running a load on the alternator and all of a sudden that load is disconnected then a high voltage spike produced will take out the alternators Diodes

[@rockskipper5353]

So changing your alternator is less work than putting adc charger inline ?

[@ontheroadwithron2432]

Probably not even tho there are mounting points on the Mercedes engine. I thought about it but only if i had decided to go with a 24volt system of battery, inverter and possibly a 24 volt mini split. It the end it was too expensive and more complicated than I needed.

[@XPRoller]

Sprinter idling for an hour? Wow!!!

[@ontheroadwithron2432]

Yes can idle up to 2 hrs then need to regen on the highway.

[@terrancemccune1424]

Thank you Grandpa Ron for your all experienced level user friendly explanation of a complex subject real world application integrating new battery tech into a tried true mechanical system. I only have one more question to figure into my application to find the answer . 52 v 30Ah lithium high end ebike battery to power led light strip a rice cooker 350w and laptop phone charging 1500- 3000w power drive inverter upgraded Toyota alternator 120watts I believe 14.7 volts at normal load . Do I need a different inverter to handle and limit the 52v DC, down to 12v DC that as of now provides very effective alternator charging and appliance powering from the stock lead acid starter battery while motor runs and for 30 minutes, after the motor is off before it auto shuts down at 12.2v with out any starter battery issues , looking for 4-5 hours of charging after the engine and alternator is off provide 110 ac with out catastrophic component failure. any accurate honest information from forum users would be valued .

[@ontheroadwithron2432]

Let me be sure. Do you want to use the 52v bike battery to run your 12v appliances when the engine is off? In that case a 52v to 12v charger would be needed. If you just want to recharge this battery then you have to use your inverter to change the 12v from car battery to 110vac. You can then charge 52vdc battery with you battery charger (110vac to 52vdc).

[@quartamile]

Interesting video, thanks for sharing. I don't think the issue has anything to do with amperage; I think the issue is voltage. 12v lithium batteries often call for about a 14.5v, and most alternators cannot guarantee to offer quite that high of a voltage. I personally wouldn't mind paying a couple hundred bucks for the DC-DC charger to get the full lifespan of the battery due to proper charging. Maybe I'm missing something.

[@ontheroadwithron2432]

I believe your concern about proper voltage is a carry over from lead acid batteries. Lithium batteries last a very long time and do not need to be fully charged. Over charged will shorten the life of any battery, lithium included. My solar charger shuts off at 13.7 volts for some reason but I don’t mind as I have 4x the energy that I used to have with my old 6v golf cart batteries. No need to charge them higher. My alternator puts out 14.4 volts so I could charge them a bit more but that could also shorten their life a bit. My lithium batteries are actually made for solar backup for home use and are warranted for 10 years. That is charging and discharging in every day normal usage. If you have a low power alternator then a dc to dc charger is not a bad idea.

[@SalmonKing52]

Ron...where did you gind that soec adjustment note?

[@ontheroadwithron2432]

I think spell check garbled your message.

[@jackdbur]

You could also fit Mercedes own liquid cooled alternator their fairly cheap second hand.

[@20111111jorg]

Perhaps I missed something, but lithium is suppose to change around 14.4 or so. Does your alternator put out that kind of voltage?

[@ontheroadwithron2432]

Yes it does. Might be a bit lower when charging.

[@flynmoose2227]

This may be true for just charging your battery. But if you have an idling motor, inverter on (2KW) and use a heavy load - I can attest that you can (almost) smoke your alternator. I could smell it getting hot and shut everything down pronto. I will be installing my Renogy DC-DC soon.

[@fratermus5502]

Idling with any heavy load is an unforced error.

[@ontheroadwithron2432]

What year is your sprinter? The older ones do have smaller alternators. And yes, i will not normally be idling the engine. This was just a test.

[@koertdubois6781]

Based on discussing this with knowledgeable friends over the years, I’ve come to the conclusion that it’s entirely possible to charge the lithium coach batteries via a direct alternator connection. But, this should never be attempted by anyone but an electronics expert who has their hands on the controls, ready to throttle down the charge rate.

[@geoffmooregm]

@@koertdubois6781 You likely won't get full charge either. Lithium Iron batteries need a boost voltage of 14.6V in order to get to 100%. You will be about 1V shy if you just use a regular alternator. Or if you have a dead lithium battery they will pull A LOT of current right when you connect the alternator. I have a Renogy 50A DC/DC MPPT charger that will do alternator/converter or solar and will also blend them so I am quite happy with it.

[@koertdubois6781]

@@geoffmooregmIt really needs to be considered in terms of the existing configuration and the owner’s needs. I believe in having as few connections as possible between our Sprinter and the Winnebago coach. Except for the few devices that can’t be completely separated (steps, levelers, slide-out) the only connection I have is alternator -> Charge Mate -> coach batteries. And that connection is switchable and normally left disconnected. But, when it’s needed, I can choose between 80 and 150 amps from the alternator, plus 80 amps from the generator for either 150 or 220 amps of charging.

[@conradcoolerfiend]

Am i understanding this right? You are relying on the smartness of the alternator to limit the current? And then size the wires to that maximum the smart alternator limits the current max to? And wire the lithium batteries directly to the alternator and not to the starter battery?

[@ontheroadwithron2432]

Whatever the case, I’m only getting 70-80 amps charging going into the lithium battery pack. Even when battery is down to 20%. I don’t think the alternator itself is limiting the current as this is much lower than its rating. My best guess is the the voltage drop from the long cable length is the main reason.

[@Iamandthatiam]

how is this set up working for you a year later?

[@aandrewin5711]

I have been a Certified RV Technician for about 30 years. So JM2C.... Can you get by without using a DC/DC charger for your lithium batteries? Yes you can but is it the smart thing to do? In my opinion I would say no. I heard the arguments about what amperage modern alternators are capable of and then some. Your alternator was designed to provide charge to your chassis battery and keep up with the accessories on the "CHASSIS" side of the rv and "CAN" handle charging wet/agm batteries. Just because your alternator outputs ??? Amps don't mean you should add that unnecessary load to the chassis charging system. They have been doing that for years but now we have better batteries and more installed items in these units that require a larger demand (Inverters, House refrigerators etc.) Why not use a device such as a DC/DC Converter to help carry the load to help keep your batteries charged. Your alternator will thank you for it in the years to come. Lithium is a different story and requires A Constant 14.6v to charge efficiently. I seen one guy respond "How is your alternator holding up" LOL Just because you don't see smoke coming out of it on the few trips you've made don't mean you are good to go. You paid good money for lithium so follow through on the complete system. I understand there are devices that are marketed to drain your wallet/purse but I would not cut corners to save a buck. I have seen another guy respond about a DC/DC charger being a marketing gimmick and it is B.S. Are these guys happy they don't have to fork out a couple hundred bucks for a piece of mind? Maybe. Its your coach/trailer and your money. This post is not to bash the author of this vid but to shed light from a technician's point of view. Either way you go. Enjoy!

[@ontheroadwithron2432]

I appreciate you taking the time to reply. I’m a mechanical engineer with a degree in physics for reference and do not say I know everything but I am also comfortable without a dc to dc charger. Especially since the alternator charging is used very infrequently. Solar is the main method to charge my battery. If I didn’t have solar my decision may have been different.

[@victorjcano]

AS I UNDERSTAND IT, IT'S NOT THE CURRENT THAT IS THE PROBLEM BUT WHEN THE BMS IN THE LITHUM BATTERY SHUTS DOWN THE CHARGE THE BACK EMF WILL TAKE OUT THE ALTERNATOR DIODES. THE DC TO DC UNIT PROTECTS THE ALTERNATOR

[@MatejFabianek]

​@@ontheroadwithron2432I agree with the RV guy that a DC DC charger is a must. Why is your charging current only 70~ Amps? What is the limiting factor? As the batteries when empty can take a lot more.

[@chrisr819]

Its very simple, if your alternator has a sufficent internal temp control like eg the 115A Mitsubishi or 125a Valeo then the alternator protects itself from overload by dailing back when too hot. This is already needed for big AGM or banks of multiple AGM in parallel also have a very low resistance nearly equal to lithium and will also burn the alternator if it doesn't have internal temp control. These with internal temp control with AGM lead regulator can be connected to charge lithium directly when you put in an argofet splitting diode and charge a lead via diode in parallel to your lithium. This is because the BMS of the drop in or DIY battery will cut off earlier when alternator still charging the Lead but because lead is there you don't get a surge and a spike when disconnecting. It is bs that a lithium need a constant 14.6V charge voltage, a typical charger like my victron multi or phönix actually starts much lower at about 0.3-0.5V above battery voltage to no unnecessarly stress the cells. The lithium will still suck in all current it get, doesn't matter if 14.6V or just 0.5V over battery voltage. Maybe you loose 5% in worst case, doesn't make economically sense to modify this alternator as with doing that you loose its internal temp protection and gain therefor maybe 2%.... I did competition car strereo for over 20years, been european champion and dealing as long as that with lithium, first from a scrapped military vehicle 20 years ago when noone beside military and some geeks know they exist. So i know a bit about alternator charging with Lithium, lifepo4 and also LTO. Now living aboard a catamaran sailing around the world and help other sailors install or fix their lithium system for the rum kitty. Tried all, burned several alternators and also a car.... learned my lessons by trying and learning, competion car audio is going to and above limits so we tried always to squeeze as much as we can....

[@chrisr819]

If your alternator doesn't have sufficient internal temp control you need to modify it to external regulation or use a DC2DC at max 50% of rated alternator output to limit the current. What saved thousands of alternator are unintentionally insufficient install like underdimenioned cable or corroded contacts or battery terminsl grease inbetween means that created a high resistance and protected the alternator from going full flat out till it burns....

[@SheikhN-bible-syndrome]

The issue is lithium need the consistent voltage and amperage when charging and does not do good with a high float voltage thats constantly being pumped into it while your driving do to its low resistance literally it likes the exact opposite of what lead acid batteries like and so although you might not overheat and damage your alternator you will wear out your lithium Bank by charging it wrong

[@ontheroadwithron2432]

Thanks for sharing. The manufacturer of the lithium battery recommends a charging current of 80 amps. The BMS will limit the max charge to 100 amps. The battery protects itself.

[@fratermus5502]

> lithium need the consistent voltage and amperage when charging Are you making this up? > and does not do good with a high float voltage thats constantly being pumped into it while your driving So disable the relay when they're charged. And use punctuation.

[@mendozaconsultation]

Question...Can i connect my 10amp pmw solar charger to my car battery so i can charge my sla secondary battery while driving like a Isolator.?

[@ontheroadwithron2432]

All DC chargers will work together so yes. Your solar panel will charge any battery it is hooked up to. My solar panels are charging my coach battery while I am driving.

[@johndesousa7379]

True a DC to DC charger is only needed when the Alternator is too small. Better to buy a larger alternator.

[@matthewknight5641]

I use a 24 24 victron DC to DC charger but it's because I have a 21 kw lifepo4 battery and a 14 kw Nissan leaf battery. My lifepo4 is the main battery but if it ever drops low enough then the leaf battery connects and dumps it's energy into the lifepo4. I have a huge amount of battery but we need the large capacity because we cool and heat with a 9000 BTU mini split

[@ontheroadwithron2432]

Wow that is a huge battery pack. I’m surprised the DC to DC charger can supply enough power to charge them.

[@matthewknight5641]

@@ontheroadwithron2432 the DC to DC only pulls from my Nissan leaf battery to put a little juice back into my lifepo4 battery. The leaf battery charges from a victron charge controller during the day and the lifepo4 charges from 2 big victron charge controllers during the day. I'm only home a few days a month so my inverter is turned off for about 3 weeks at a time so there is plenty of days to charge then only drawn down for a few days then I'm gone again. It's how we have electricity without a monthly bill but I've spent well over 30 grand on components to be able to not have a monthly bill lol. It's more of an expensive hobby than anything but it's fun

[@DSKSeattle]

I think the biggest issue is that Lithium batteries outputs 13.3-13.4 volts, whereas lead acid outputs 12.8-12.7. That means your alternator would need to be charging at 14-15 volts to charge the lithium battery. My 120-volt AC charger outputs 16 volts DC to charge a “12-volt lithium”. That’s what a DC-DC charger could do (with step-up). I suspect that your alternator isn’t charging your lithium battery to 100%.

[@ontheroadwithron2432]

Of course lithium does not need to be fully charged after using it. My solar charger cuts off charging at 13.7 volts. The alternator output is 14.4 volts so that will fully charge the battery until the BMS turns the charging off.

[@victorjcano]

I UNDERSTAND IT, IT'S NOT THE CURRENT THAT IS THE PROBLEM BUT WHEN THE BMS IN THE LITHUM BATTERY SHUTS DOWN THE CHARGE THE BACK EMF WILL TAKE OUT THE ALTERNATOR DIODES

[@fratermus5502]

> your alternator would need to be charging at 14-15 volts to charge the lithium battery. LFP will happily charge to 100% SoC at voltages as low as 13.6v.

[@victorjcano]

@@fratermus5502 what does LFP stand for??

[@fratermus5502]

@@victorjcano LFP = LiFePO4

[@duotronic6451]

Great point. Victron will sell you a 10mm bolt for $200 if they get a chance.

[@SalmonKing52]

@ontheroadwithron… Hey Ron….you got any updated on this?

[@ontheroadwithron2432]

Cross country trip coming up. I have used the alternator for short term charging but as long as sun is shining the solar is the main charger.

[@sailingmsmalachite1503]

I’m lost now so I don’t need a dc to dc if I changed my wet Leed to lion battery 🔋 ???

[@ontheroadwithron2432]

Depends on your setup. If you change to lithium, just measure how much current the amp meter is reading while charging the batteries. If under 80 amps you are good. Personally I installed a switch to turn the alternator charging off. Not necessary but I usually charge the battery using solar and don’t need to run the engine to recharge.

[@burli0071]

You are the Best👍👍✔✔💖💖

[@markpillori]

I thought Mercedes recommends never idling the engine, that it is bad for sprinter Diesel engines. I think in your test you idled the engine for an hour?

[@ontheroadwithron2432]

MB says 5 minutes to idle if using biodiesel. Regular diesel up to 6 hrs.

[@craigmarshall5896]

The thing to understand about Victron is that their main market is 'marine', no airflow over an alternator. Boats typically come with anything from 40-120A alternators. Marine engines will also normally be running on a mooring at lower idle speeds. The DC-DC chargers can be placed in parallel, so 2 x 30A = 60A to charge. You also have to appreciate that the Orion TR is a three stage charger so is designed to maximise your battery service life too. You also get the protection of voltage disconnect too. If or when your alternator regulator fails the Orion won't allow the increase voltage pass to your domestic system. This video does a reasonable job of doing an explanation of why you might want to use a DC-DC charger: kzbin.info/www/bejne/o6rbaKmZarSgo5Y The other thing people miss is the cable sizes required to carrying the current they are generating at their alternator. 2 x 140A alternators = 280A that will need at LEAST 50mm2 cable, plus fuses etc. The cross-sectional area will also need to increase with distance too, even over a few metres. Lithium can typically sustain a charge rate of C0.5 or C1, so can often suck up whatever you can throw at it, especially a depleted bank. Personally I always use Victron, because you generally get what you pay for, and you can save money from what you don't need when you have something like this.

[@chrisr819]

Your wrong, the main market is by far RV about 15-20times the one for marine... But you are correct in marine i would assume 80% of alternator are selfregulated dumb as toastbread alternator that needs external protection. As a rule in marine (with exceptions as always) if you have a V-belt its a dumb one, if you have a serpentine belt it most likely has internal temp control and can protect itself, no DC2DC charger needed. Well known and widespreaded are the 115A Mitsubishi and the 125A Valeo found on the newer leasure boat engines from the big 3 Volvo,Yanmar, Beta till 100hp.

[@bigblockcutlass123]

How many amp at 2000rpms? How hot does it get then?

[@ontheroadwithron2432]

I didn’t see much difference in output at different RPMs.

[@jeffreyumeh8580]

Ah considering my van my house like reliability is king so I'm going to use a DC to DC charger, also because I have 885W of solar undeployed and deployed 1770W of solar with 1200W of foldout solar pannels so a total of 2970W of solar, I live in the UK though so I need a lot of solar to fill my batteries during the rare sunny winter days and with 2970W of solar even on overcast days I can still get 75 - 100W which is enough to power all my vital loads which is the fridge freezer, diesel heater, lights, phone charger, heater for the battery compartment etc. And yeh the fridge freezer when it's already prechilled over a 24h period only uses like 150Wh so a couple of hours my fully deployed system even in overcast conditions is enough to run my fridge for 24 hours. The orignal point is that I only need a little extra power from the alternator to pick up for the times when I haven't had a sunny day for a week or 2 if I am just running vital loads, so a 20A 48V charger is all I really need and that isn't expensive by any means.

[@ontheroadwithron2432]

Yes this time of the year is challenging to get enough solar. DC to DC chargers are very reliable and is s good solution especially if the alternator does not have enough capacity to charge the batteries.

[@Skits_Missions]

Check battery warranty details. You WILL void warranty on the lithium battery if you do not charge with lithium profile charger.

[@ontheroadwithron2432]

I have read the warranty. The BMS safe guards the battery. It protects from borh under and over voltage. There is no special charging profile for lithium batteries like the lead acid type. Just charge til full and then BMS will disconnect the voltage from the charger.

[@Skits_Missions]

@@ontheroadwithron2432 you need to reading again! You are post BS that could get people to lose warranty and have a BMS trip on them and not know how to reset. While camping, on the ocean.