Charging Lithium Batteries with My Boat's Alternator

Gary sent us a question about his lithium batteries. He said, "Jeff, thanks for all you do for the marine industry. I particularly like your longer seminar videos. I am installing 4 X 170Ah 12V LiFePO4 house batteries in parallel that are combined with a 4D AGM start battery via a BlueSea automatic charging relay. Each battery has its own BMS.
My concern is for a scenario where all BMS’s shut off the charging input. Will the AGM absorb the load without a momentary disconnect from the alternator causing the alternator to run without a load blowing the diodes? The regulator is externally controlled via a Balmar 614. Any other red flags on my install?"
Read our Tech Talk Article from Pacific Yachting Magazine, "Can You Have Too Many Charging Sources for Your Batteries?", www.pysystems....
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[@brianbuchanan5170]

Excellent. So many people want lithium without really understanding it, or the comprises built into the BMS of “drop-in” replacements. As noted the lithium could potentially “go dark” due to too high of a voltage. If using a battery isolator then there is potentially no battery in the house circuit. Major issue if any high draw item is turned on as the alternator, and likely the isolator, will not handle it. That’s why I’m a fan of the firefly batteries you promote. Lithium really needs separate charge/draw bus topography, with separate automatic disconnects, so it can continue to provide loads (if over charged), or receive a load (if undercharged). That and all chargers need to be properly configured to limit charge voltage (measured at the battery).

[@PacificYachtSystems]

Hi Brian, thanks for chipping in the conversation, one Lithium battery manufacturer that has both load and charging sides is the Lithionics battery: lithionicsbattery.com/

[@nickcancro7927]

You’re solving one of two problems. The other being too much current being drawn by the lithiums and cooking the alternator

[@BlackheartCharlie]

Exactly why I went with two Victron DC/DC chargers. I can regulate the current going from the engine to the house bank. I'm not sure why Jeff Cote didn't address this in the video or in prior questions. Jeff - what do you think about this option?

[@stephenburnage7687]

Good question. That's my number one concern. This could overheat the alternator and break down the insulation on the cabling, potentially leading to fire.

[@alexsails80]

@@BlackheartCharliewhich of the victron dc to dc chargers did you use? Been waiting for the XS model. Isolated or non isolated model? Thanks

[@BlackheartCharlie]

@@alexsails80 I have two of the 12/12 30 Orion's in parallel. They are the isolated version. I don't know if the non-isolated ones also run hot. I'm starting to see that the 12/12 50 XS model is shipping. Hopefully it doesn't cook itself like the Orion's! B.

[@giovannifiorentino8947]

Jeff, great subject. My only suggestion to enhance it is to accompany the explanation with a superimposed diagram.

[@dankellybalmartechnicalsup9992]

Great explanation Jeff. I echo what some else said in that so many people want to install these lithium systems without understanding them properly researching them and understanding this is not a one size fits all. Please do your research understand there are many ways to go about it with drawbacks to each. If you don't know what you are doing please have a qualified system designer check over your design who has some experience with these out in the field. We get calls from even installers who still don't quite understand these systems. We offer a wide variety of products such as our new 618 regulator with preprogramed lithium settings and and wireless monitoring and specific programing through our SG200 and app. Also adjust the belt load manager to limit current if you find your alternator is heating up to quickly. It is imperative that the alternator temperature sensor is connected and working properly to not risk damage to the alternator with these systems.

[@PacificYachtSystems]

Hi Dan, thanks for having Balmar Technical Support group join the conversation. We've installed hundreds upon hundreds of Balmar products over the years and are a big fan!

[@dankellybalmartechnicalsup9992]

@@PacificYachtSystems Thanks I have learned a lot from from Jeff understanding these systems a wealth of knowledge. It would be cool to see Jeff do an unboxing of our new 618 regulator and sg200 battery monitor which allows instant advanced programing through a phone app rather than the older magnetic screw driver method.

[@svDansleau]

I'm pretty sure that the Balmar 618 has a safe guard against termination failure and as a backup install an APD(Alternator protection device) This way you can utilize as much of your Alternator as you want and charge the starter bank from the dc-dc. I use 150amp of my 170amp balmar with a large exhaust fan in the engine compartment. Sv Sandii

[@michaelw3809]

I think the battery isolator does not restrict the amperage going into the lithium battery and may cause the alternator to die of heat exhaustion. Please correct me if I'm wrong

[@alfredochiappini1056]

I know I'm not Jeff, but yes you are correct on that. You will need a DC to DC converter to regulate amperage

[@haydenwatson7987]

Thanks for the video. In your screen shot of the isolator, you show the ArgoDiode and not the ArgoFET. Any reason and do you prefer one over the other? I installed an ArgoFET in my system to eliminate the 0.7v drop on the diodes.

[@qchatgreg]

not sure why youndidnt mention a “third” method? use B2B charger from alternator/starter battery (AGM/SLA etc) to charge house (lithium charge profile etc) … alternator “always” sees the start battery .. so its protected, and the B2B will boost as reqd the input voltage from alternator/start battery to whatever is reqd for its charge profile on house battery ..

[@PacificYachtSystems]

Thanks for sharing Greg.

[@gpib2028]

Good information and good timing for me - using the battery isolator and considering that the charge profile is different between the AGM (lead acid) and Lithium batteries (assuming LiFePO4 chemistry), where do you connect the external alternator regulator voltage sensing wire? The AGM or Lithium battery? Or some other way? Could a DC to DC converter be added into the circuit to charge one of the battery's at the correct profile?

[@PacificYachtSystems]

Good question, it's a toss-up since both batteries might want a different charge curve. The voltage sense wire should be connected to match the charge profile chosen in the external regulator. Some boaters will chronically undercharge the AGM battery (less then 14.4 - 14.6 volts for a 12 volt AGM battery at bulk) from the alternator and rather have the Lithium battery get the correct charge curve. The AGM start battery can be charge adequately with solar or battery charger.

[@hotnip4444]

@@salishseathings I think that the LIFePO4 BMS will limit the charge current going into the batteries

[@hotnip4444]

@@salishseathings That is one way to limit the current off course

[@JeffreyFay]

I don't know the answer but would it no be prudent to ditch your start battery and replace it with a small LiFePO4 battery? If you did this would there be a new problem with having a different capacity start battery to the house bank?

[@paulainc]

Hi!! Jeff, you don't mention that Li and AGM batteries have deferent charging profiles. Also your not mentioning, or I missed it. As to which battery type the regulator is set to. With ether setting the way you have it. You may not get the most out of ether battery. Since one type or the other is not being charges to their settings/profile.

[@martinlacroix6200]

Good one Jeff, is having the alternator connected to the engine AGM and having a DC to DC charger could be another good alternative ?

[@PacificYachtSystems]

Yep, that definitely works.

[@kkots]

@@PacificYachtSystems I don't understand why you didn't mention the DC to DC charger as an option? It is definitely a great option and probably the best compared to what you offered unless price is an unmentioned consideration. I love your videos and appreciate your expertise on the issue.

[@jelleklinge9743]

noWell, that would be a preferrable option, normal altenators don''t like the low resistance of lithium battery''s during idling or high load the alternator will overheat and fry itselve. Please invest in a good Victron DC/DC charger or an special DC boost charger (Expensive)

[@shawnswallow3595]

I apologize if this has been covered in the comments already, but in my setup, the alternator seems to be connected to the BOTH ( Common ) post of my battery selector switch. I have an AGM starting battery connected to switch position 1 and a Lithium battery ( house ) connected to switch position 2. The batteries have their Negative terminals connected together. My question.. if I want to charge my lithium off the alternator... would it be OK to start the engines with the selector switch to BOTH so both batteries charge? Not sure if I need any type of DC to DC converter or if the switch in the BOTH position would just split that voltage and just allow voltage to continue to travel to the AGM in case of the lithium BMS shutting down. Basically protecting the alternator by always having the AGM connected.

[@TMODCustoms]

In your example, what would be the difference between running the Argodiode vs a ArfoFET (I have the 100A one input, 3 output between my alt and house \ start batteries). I'm asking because I currently have my single engine alt charging my starter battery and 8d house battery but I want to replace my 8d with two 100AH lifepo4 batteries. I'm trying to figure out what other components I need, I was thinking I needed a dc to dc charger as well but I'm not sure if I should keep the FET in there as well.

[@dustindusty2]

I'm just looking into lithium batteries as my agm is wore out. I have a evinrude 40hp etech motor. I'm wondering how well a boat motor will charge a lithium battery as the voltages do not match? Can a lithium run as a starter and be used to run the electronics on my boat? Or to use lithium in a boat do you need to batteries two make it work? I've looked at renogy dc-dc charger to use if two batteries are needed but this starts to run up the cost.

[@ZILAwelds]

so your 13.8 volt output alternator can charge your lifepo4 battery bank that on paper requires 14.4 volt to charge ?

[@denispatrick4046]

I have a follow up question. I purchased a lithium power station battery, Yoshino B4000, to run may boat’s AC on anchor. I typically charge it when on shore power, but is there any potential harm charging it while motoring? I use my 2000watt inverter and charge the power bank via its AC charger (1800w). Any potential harm to the alternator or other boat electrical components? Thank you!

[@skypallman6169]

So I'm thinking about going to a lithium battery for my stereo "house battery" replacing house Agms. I have a victron battery isolation fet. Bought the 3 battery 200amp model. I upgraded to a 160amp high output alternator. My alternator has a wire to let it know when the battery is fully charged. How does that work? Will I be ok going to a lithium battery for my house bank and keeping the AGM as the starter battery using the battery isolator? Thanks for your time.

[@JW-zt9hz]

hi, just bought an Ionic lithium starter battery. Looking into using my yamaha 200 alternator to power pure (no agm) lithium house and battery banks while underway. also have a chargeverter to power the ac while underway and power all batteries dockside - just trying to figure out how to wire it and what I need. thanks

[@ericblackburn9829]

Hmmm…. I’ve got my mv-614 controlled alternator connected to my Lifepo4 bank. Then I have a b2b charging the agm starter from the Lifepo4. I have a switch in the dash to turn on and off the regulator as own primary means of charging is solar. Would the Victron b2b protect from a bms cutoff? Also, the problem I see with the isolator is that my regulator is set 14.1 volts abs for 5 minutes rather than an agm profile.

[@PacificYachtSystems]

Hi Eric, the B2B charging converter would certainly help reduce the chance of the BMS sensing overcharge.

[@stephenburnage7687]

The charging voltage of the typical lithium battery is 14.6V (13.6V at rest). The equivalent voltages for a AGM, orl gel battery are 1V lower (or more). Those voltages are high enough to trigger an automatic combiner, strapping the two types together in parallel. Doesn't that mean that the lithium will constantly seek to charge the other, and does that reduce life expectancy?

[@davidadshade2927]

Jeff, I thought you couldn't mix AGM and Lithium with an ACR due to the differences in charging voltage. Does the BMS make this possible? Thought you had to use a DC-DC charger. Please advise.

[@PacificYachtSystems]

David, in this case the AGM battery is sort of sacrificed and will not really get what it needs. Your right, AGM and Lithium want different charge profiles and you'd generally would use a DC to DC charging converter to charge.

[@hotnip4444]

@@PacificYachtSystems Why not use a Battery to battery charger. I that case you could dial in the correct charging current profile for the house LIFePO4. Another possibility is an alternator to battery charger which can charge house and starter battery at the same time. Sterling makes one which at the same time can monitor the alternator temperature as the lithium can draw an extreme load which might overheat the alternator

[@tlgibson97]

I have two alternators on a single engine. A 135A charging the two AGM start batteries and a 245A charging the three (now two) 198Ah AGM batteries. Since one of my house batteries recently bit the dust I am looking to upgrade them to lithium (Approx 600-800Ah). What would be the best recommendation to charge the lithium with my setup? Have both alternators charge the start bank with enough battery isolators to charge the lithium bank or is there a better way to charge the lithium directly?

[@garyshoulders1676]

you suggest using a diode or a battery combiner. but the batteries are two different chemistry's? surely they need different charging algorithms?

[@ralph9987]

Gidday Jeff. Interesting video, thanks. I am thinking of a similarly set up, but will have one lead acid starter battery, one AGM bank and one Lithium bank, all 12 v. How would I best integrate the battery isolator and a DC/DC charger. I was thinking of placing the battery isolator after the alternator with one connection to the starter and the second to the AGM bank, then connecting the Dc/DC charger between the AGM and the Lithium bank. Would that be the correct way to solve this? Thanks for any comments

[@PacificYachtSystems]

Hi Ralph, sounds like you are going the right track. The DC to DC charging converter is a good way for the Lithium to get a charge from the AGM bank.

[@ralph9987]

@@PacificYachtSystems thanks Jeff. What about the placement of the battery isolator, any thoughts on that please?

[@James-cv5tx]

I was wondering why you didn't mention DC to DC charger as a way to charge both the AGM Starter and then onwards to the Lithium House battery ?

[@projecttrawler]

Yeah I was thinking the same thing

[@PacificYachtSystems]

Hi James, your correct a DC to DC charging converter is a good way to charge different battery chemistries.

[@justintyme1449]

Wow! Did not know that a loss of load would kill the alternator 😲..... I better explain my plan....I have an RV project, 12 volt electrical system for the drivetrain/ 24 volt system for the house batteries along with 24 volt charging.... My plan was to add a second 24 volt deep cycle alternator to the 12 valve Cummins Diesel engine to charge the house batteries if they got low while driving. so I did hear your solutions, now my question is, if the 24 volts are being directed through the battery controller, and inverter and no other systems are feeding it power, would that be enough to keep the alternator from running without a load?

[@SailingCAVU]

I have a similar setup with 4 li and a lead acid start and gen batts. I’m using the 250a Balmar Tx with mc614 regulator. Will using the battery isolater allow me to still program the mc614 to get the max from the alternator? Balmar suggested adding an APM-12 alternator protector.

[@PacificYachtSystems]

Yes. I would put the mc614 battery sense wire directly on the li bank. The other batteries may end up being slightly higher voltage but that is a good thing as the setting for the li charging voltage is likely lower then flooded anyways. Get a low drop isolator like the victron argo fet. Don't use an old diode style one. make sure it can take 250a. if the Li BMS opened the alt still has a path to the start battery so the protector is less needed. But won't hurt anything by adding it.

[@lmbfr1]

thanks

[@barrysiler1443]

Why not use a 12V to 12 volt DC battery charger. It seem to me that the battery isolator won't output the correct voltage needed to fully charge the LiFePO4 bank, they typically need a charging voltage of 14.4 to 14.6 for a full and cell balanced charge?

[@sboubsis]

Hi Jeff, love you videos. Question. I have 2 outboards Yamaha 200 with 2 AGM starting batteries and 2 AGM house batteries. Now I need to add one 344AH lithium battery for seakeeper one. How can I connect the lithium to be charged well the engines are running

[@PacificYachtSystems]

how is the house bank currently being charged from the engines? acr / vsr ? aux charging leads? Either way I would recommend adding two dc to dc chargers, one from each engine battery to the new bank. that way both engines can charge it. ideally you'd want more charging power then the Seakeeper is using but you also don't want to overwork and overheat the alternators. so the DC to DC will limit the current being taken from the engine. and also provide the correct charging for the lithiums once programmed A pair of 30a Victron Orion smart dc to dc units would likely work well. Depending on which seakeeper you have 60a may not be enough to keep up. But 30a is probably a good max number to take from each outboard. at the end of the day when you plug in, the battery charger that charges the engine batteries would also charge the new bank via the same dc to dcs. so you wouldn't have to add another shore charger

[@patrickdavis8884]

Could a system like “bluetti AC 300” with their B300 batteries be used in a marine application? Thanks

[@PacificYachtSystems]

Hi Patrick, unfortunately don't have any experience with either product and cannot make a recommendation.

[@svviolethour]

I have to agree with @danpease8395. I guess everyone can have their own opinion, but the advice in this video isn't really what I hear as best practice as of 2022 or so. I found myself wondering when you were going to mention DC-DC chargers and APMs, but it was only ACR or isolator. The Balmar APM is only $70 at West Marine so there's really no reason to use an AGM start battery as "sacrificial" protection. And a DC-DC charger isn't much more expensive than an isolator or ACR. A DC-DC charger allows you to customize the charging profile to the battery you're charging, so it's sort of surprising to me that DC-DC chargers aren't the default in place of isolators and ACRs by now.

[@donbrloks3959]

Sailboat with LA start battery and LP4 house battery. Alternator goes to start battery. Blue Seas ARC connecting both banks. Engine running,both banks connected. Shut down engine, but LP4 is still at 13.4 volts. Won’t that back feed and keep the ARC connected until LP4 voltage is below 12.75 volt or about completely discharged? Seems like I would need an ARC with an ignition connection to correct this.

[@PacificYachtSystems]

With different battery chemistries, e.g. lead acid versus lithium, better to install a DC to DC charging converter instead of a battery combiner. Recall the DC to DC charging converter will modify the voltage to what the Lithium battery needs.

[@martehoudesheldt5885]

what about the elephant in the room?? alternator signal wire (turns on/off unit) ?? which to connect it to? - leave connected to start battery and use a dc to dc to charge the other batteries ( correct volts/amps profile) for batt type.

[@PacificYachtSystems]

Certainly easier to have the alternator connected to AGM start battery and then share the charging voltage to the Lithium battery via a DC to DC charging converter. Challenge is the max output of the DC to DC charging converter is about 30 amps.

[@adamportner8102]

What's your thoughts on using one lithium battery as a starting battery on a bassboat which would also be controlling all screens and pumps as well. I have a Suzuki 250ss.

[@PacificYachtSystems]

I'd suggest going with a lead acid battery and not doing Lithium for starting applications.

[@mikerohr506]

I understand the battery isolator the thing that I do not understand is is the alternator able to charge a lithium battery? Is I use high tech battery chargers they check to see what type of battery is being charged and they pick one, I have had trouble with the won't charge different batteries even though I'm using a battery isolator.

[@PacificYachtSystems]

A properly chosen alternator with external regulator (programmed for Lithium) will be able to charge a Lithium battery.

[@bdiver6445]

Why not a DC 2 DC between the batteries?

[@1975Per]

@pacific Yacth Systems Love your videos. Been watching them for years and recommends them to everyone! Now my Q: What about those Sterling battery protection units, that are supposed to soak up the spike. Are the uesless/not necessary if you have a starter battery in parallel? Or would they still be usefull? What if the AGM is already quite full, and the alternator is running full speed, will the agm still be able to soak up the spike?

[@PacificYachtSystems]

Not familiar with the Sterling protect unit, but yes a full AGM battery could still take all the amperage from a alternator when a BMS decides to disconnect a lithium battery from overcharging.

[@davidsomers3324]

Jeff, this may be a recent developement since this video but Victron offers a "solidswitch" which was reportedly made for the express purpose of safely shutting down a turning alternator controlled by an external regulator by disconnecting the ignition wire should the BMS over voltage disconnect ckt see over voltage parameters. Balmar indicates this can be done at the same time or before a complete BMS isolation of the LiFePO's. Comments?

[@PacificYachtSystems]

You bring a good point, external BMS for lithium allows the BMS to communicate and control the alternator charging via the ign wire connect to external regulator (e.g. ign wire is to turn external regulator on or off).

[@JohnDoe-in1nx]

Hi Jeff, listening to your marvellous videos from abroad (the Baltic), where i am refitting my newly bought 43 year old sailboat, i would like to come up with a third alternative: How about using an isolated dc/dc-converter (e.g. victron Orion-TR 12|12) to charge the house-battery with the surplus from the starter-battery (to which the alternator is connected). Perhaps this is technically not any different from the solutions you mentioned because i am mixed up with all the different names of the many devices ;) Thanks and cheers, Steven

[@PacificYachtSystems]

One of the limitations of DC to DC charging converters is the max amperage (30 amps for Victron) when some alternators, can output 150 and even 200 plus amps. Some boaters are going to find 30 amps to be a slow way to recharge the lithium bank. Does anyone know of a higher output DC to DC charging converter.

[@bluemu]

@@PacificYachtSystems the Scotty that Safiery sells is a 3000W dc-dc buck boost converter. It may be able to

[@hotnip4444]

@@PacificYachtSystems Sterling makes at least 60A B2B an Think a bigger one is in development. Allready have an 60 A shorepower charger from Them an Think I will go that Way for charging my new lifepo4 house bank

[@drew651]

@@PacificYachtSystems I am looking at upgrading my house bank (lithium) and alternator (170A). I was going to use a DC - DC charger off the house bank to the start battery. Would that work? Or should I have the alternator charge the house bank and then have a DC - DC charger for the start battery? I want to be able to use as much of that alternator as possible to charge the house bank.

[@markbaldwin396]

I have a bass boat and changed to lithium batteries. I have 3 125Ah batteries for trolling motor and one 110AH battery for my engine and electronics. Will the alternator charge the lithium battery when I run? I recently noticed my volt meter on my console down to below 12 volts and my starter battery went dead on the lake. I also noticed when it was running that the meter on the console was not over 13 volts like it normally is. I will check my alternator next time out but I wasnt sure if the engine alternator would charge the lithium battery. Is there a better way to optimize the alternator charging lithium if it does work? Thank you

[@PacificYachtSystems]

Mark, you'll want to consider how does your engine alternator recharge your house battery bank, it is via a battery switch to "all" or "both" or do you have a battery combiner or perhaps a DC to DC charging converter. One of those 3 items is most likely the way for your engine battery to share a charging voltage with the house battery.

[@jamestim319]

Brilliant as usual Jeff.. What about a 24v house bank of lithium and a 12v starter battery (my case). I would love to hear your opinion if you have time..

[@PacificYachtSystems]

With different voltages, you'd have the starter and the alternator connected to your 12 volt engine battery and then recharge the house battery with a 12 to 24 charging converter.

[@barrysiler1443]

@@PacificYachtSystems See my question above but Victron make a 24volt to 12volt DC to DC charger that allows the charger to output the correct voltage output (14.4-14.6) for 12volt from the 24 volt bank. The also make a 12 to 24 DC to DC that would allow you to connect the 12 volt alternator (assuming that's what you have) directly to the start battery and then pass the excess current to the 24 volt bank.

[@rainydaykennels]

I'm slighty confused because I thought that Lithium batteries required different charge parameters then AGM or other types of lead acid batteries. Wouldn't it be unwise to parallel two completely separate battery chemistries or is the assumption that the built in BMS will sort it out? Why not use something like one of victrons isolated DC to DC chargers so you can tailor the output of one battery to the needs of the other?

[@PacificYachtSystems]

Trevor, you're correct AGM and Lithium are different chemistries and require similar but different charge curves. Some boaters, are sacrificially using an AGM battery (in parallel to a Lithium battery) as a way to protect an alternator in the event of a BMS disconnect.

[@drheaddamage]

new intro is much better :)

[@PacificYachtSystems]

Thanks!

[@peterlangan1295]

Hi Jeff, Thanks for your videos - I have elected to go with a Lithium house battery and have installed an "isolated" Victron dc-dc charger and changed my onboard charger to a model that allows separate charge profiles for the two different chemistries. Does the "isolated" aspect of the dc-dc charger infer that the grounds on my house system needs to be separate from the starting battery grounds? or is this not a concern (I can tend to over think things). Thanks, Peter.

[@PacificYachtSystems]

Good question, and I'm not sure of the answer. In this case, i think isolated means the negative on either side of the DC to DC charging converter are seperate and their no conductivity. Can someone weigh in on this.

[@philipmclean3123]

Jeff, I've enjoyed binge watching your videos, and really appreciate your educational approach. Could you talk about parallel diesel hybrid systems (such as those from Beta Marine), and how they might replace a generator in a new build sailboat or a repower project with extensive electrical upgrade assuming a greater than average solar panel installation and a lithium battery bank? I'm interested in how this would affect chosen house voltage, a realistic energy budget (just how devastating is AC?), and properly sizing the diesel engine to efficiently charge the battery bank while underway at modest speed for a few hours. The benefits, as I see them, are quiet yet powerful maneuvers in the marina, reduction of number of IC engines onboard requiring service (& noise, thruhulls, spare parts), as well as a limited source of backup propulsion should the diesel engine conk out while in the channel. Several hours of pleasant electric motor-assisted sailing might help complete an iffy daytime passage if shore power were expected at the destination, and it is more likely that the diesel engine would be operated under a decent load rather than wasting horsepower and causing carbonization. Unless its a fast boat, I don't think regeneration or cost of fuel is a major factor in this choice, but perhaps weight is? I look forward to your next vid. Thanks!

[@PacificYachtSystems]

Thanks for the feedback and the suggestion.

[@brucefay5126]

Seems that even with two alternators (engine, house), the problem still exists if the house is LFP and the BMS disconnects it. Does anyone make/use an electric clutch on an alternator? Not sure it could disconnect the alternator from the engine quickly enough even if such a thing exists, but just wondering. You also have me thinking that perhaps a LFP battery system should always have a battery isolator with the other output connected to an AGM battery. Still, it leaves open the question of where the external regulator should be connected.

[@PacificYachtSystems]

Hi Bruce, having a dedicated alternator for a lithium house battery might still get you in trouble, especially if the BMS cannot communicate with the external regulator to stop it from overcharging the lithium battery. Without comms, the BMS might simply disconnect the battery and the alternator will suddenly be without a battery to charger and likely the alternator will be damaged.

[@hotnip4444]

@@PacificYachtSystems Sterling makes a dummy load safety just for this

[@aphrodite3216]

I was just told i cant have this setup... ??? That the acr doesnt change the charging profile and therefore presents the possibility of a fire...??????

[@bobbob-s8v]

Better way not To burn up your alternator is to use a DC DC charger from your starter battery to the lithium. I use a 30 amp model works well.

[@Theoppositeofchaos]

Interesting Jeff I got two 3kw Hybrid Inverter Chargers made by Mpp Solar they are two years old my concern is what will happen if for some reason the fuse get blown,, will the Charge Controller stop charging or get damaged? Am talking about a large fuse between the battery bank and the Inverter

[@PacificYachtSystems]

Not familiar with this specific inverter/charger but don't think you would damage anything if the inverter/charger was blown. Anyone else can comment?

[@Theoppositeofchaos]

Many thanks Jeff, I have always been told to connect battery to a charge controller, before connecting a solar panel but in this case on a Hybrid Inverter Charger I get worried or wonder what will happen if the main fuse blows because if that happens it means the Controller is not connected to the battery bank.. I started thinking about this today when you were explaining the dual battery scenario...

[@anthonymarino4260]

thanks for sharing

[@PacificYachtSystems]

My pleasure

[@jeremystevensonjs]

how exactally does an altenator "blow up" if it looses connection to a battery? an altenator does not even have to have a battery to function. it will keep the engine running off its output voltage until it is either shut off or reconnected to a battery. loosing connection to a battery will not effect the altenator.

[@PacificYachtSystems]

.

[@fkordalewski]

@@PacificYachtSystems Good question Jeremy, but I don't see the answer from PYS. Thanks.

[@explorationoverland6782]

Would this also work with a Victron Argo FET?

[@PacificYachtSystems]

The Victron ArgoFet is our favorite battery isolator

[@rpspp]

What if I don’t have a agm battery but both are lithium

[@PacificYachtSystems]

if you are charging a lithuim battery directly from an alternator, you have a risk of the battery BMS opening, which could fry the alternator. There are alternator protectors that may help prevent the damage if that happens. if you only have lithuim, the correct way is to have an external BMS that can shut the alternator off first.

[@junklist99]

Jeff, How do Victron AGM Deep Cycle Battery compare to Oasis Firefly

[@PacificYachtSystems]

Good question, don't know as we've never tested the Victron AGM deep cycles. Anyone else can chime in and compare them?

[@johndantin5203]

Hi Jeff, Just found this video and it got me thinking about my setup. 4 Relion RB100 batteries in parallel with an Optima Blue top 31M as a start battery, the Alternator is a Balmar 120Amp alternator controlled by a Balmar 614 regulator. After looking at the video I checked my charging relay and saw it was a Blue Sea M-ACR 7601, which appears to only handle 65 amps. My impression afte watching the video was that this design should be adequate to protect the alternator, but I am questioning whether I should upgrade the charging really to the SI-ACR to handle the higher amperage.What are your thoughts? Thanks, John

[@PacificYachtSystems]

Tough question and unfortunately no definitive answer. Assuming your AGM optima Group 31 is not heavily discharge, your alternator is connected to your Relion bank, you normally should not have lots of amps going from your Relion batteries to your Optima Group 31. As with all battery combiners, regularly check the fuses on both sides of the circuit for accidently over amperage.

[@danpease8395]

Jeff, great talks, BUT, is this combiner smart. NO! It is not. You will be doing a dis-service to your lithium bank by charging in a non specific form. You really owe it to your viewership, to either modify this video, or take it down and tell people why, as pointed out by others here, use a smart b2b charger, and not limited to that protection. You should also, in EVERY video when yo talk about any combination or lead and lithium batteries, NEVER NEVER NEVER directly connect the two different chemistry battery banks together unless you are ABSOLUTELY SURE that the banks are perfectly equal in voltage state. Please man, protect these people.

[@PacificYachtSystems]

Thanks for sharing Dan, appreciate it.