Charging the Bus Batteries with the House Batteries

Today, we are sharing a quick project that took one “to do” off our mental checklist. Since moving our workspace out to an off-grid property, we are not driving the bus very often. Therefore, our two 8D chassis batteries are not being charged regularly. We used to simply hook them up to a plug-in smart charger periodically to keep them topped off - when we remembered. However, we found a better way to solve that problem which means we don’t have to think about it anymore. An MPPT solar charge controller.
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About Us:
A family of six dreaming, planning, and preparing to full-time RV around the country. Renovating our '64 GM PD4106.

[@bobf.7238]

How is this going, Juan. I wanted to do this but then, in the manual, I read the following. Quote; "Avoid using the solar charger as a DC-DC charger (e.g., to charge a 12V battery from a 24V battery bank). Connecting a battery to the PV terminals under certain operational conditions can damage the solar charger, which is not covered by the warranty. Instead, use a dedicated DC-DC charger or converter. Check our DC-DC converter product page for a complete product range". I read elsewhere on the Victron site that under certain conditions, the charger will short the PV input with an internal relay. It said that this is OK with solar panels but not with a battery or power supply. See section 8.12.10 through 8.12.12 of the Victron MPPT Solar Charger Manual. The smallest DC-DC charger is to big for my space so, instead of connecting my 12 Volt lithium house bank to the PV input of my Victron MPPT, I used a $14 "short protected" DC-DC step up converter from Amazon in between. So far, so good. This also satisfied the requirement that the PV input be 5 Volts higher than the battery to start charging.

[@minutemark]

Every Prius needs this!

[@BeginningfromthisMorning]

Thank you Mark!

[@sanjeevbhalla2506]

beautiful integration ....with MPPT in place of DC DC charger ... reducing cost ...BRAVO

[@BeginningfromthisMorning]

I was warned many times that it would not work well or last. We have had that little charger in for over a year and I have yet to hook up any external charger to my starter batteries. This little hack has worked very very well for us.

[@offgridtruckerdude7133]

OMG ! That was a mighty good idea. I'm installing 1200ah backed with shore power, 7kw gen set, 600w of solar in my semi truck, and have been knocking my brain on an efficient way to keep starter batteries charged while in off grid mode

[@edwindaxton175]

instaBlaster.

[@paullawrence8394]

That’s what I call thinking outside the box. Excellent idea. 👍

[@BeginningfromthisMorning]

Thanks 👍. It has been working great!

[@royrobbins2214]

Juan, I've been doing something similar for a few years. I took the 12dc from my truck alternator and stepped it up to 48vdc to run from my truck to my trailer MPPT EpSolar charge controller to charge my 16 volt Leaf batteries . By doing that, I can create my own profile, as I have for my solar already. I also remote monitor it over RS-485 and a Verizon MiFi

[@kevinhornbuckle]

Clever.

[@jnjentinc]

Ok im sold lol... AMAZON I NEED MORE PARTS 😆

[@alanblyde8502]

Victron have some amazing products, you have a top setup there 👍🇦🇺

[@brycejeannotte7699]

Just a quick comment about wiring. In your wiring bay, above all of your white cables for 120V there is a wire nut (Marrette) sticking out. These are great for use in house wiring. They have no place in mobile wiring such as vehicles, marine, etc. I know they are quick and easy, but they are not vibration resistant and therefore not a good idea. You are doing everything first class on your bus so I thought I would mention it.

[@BeginningfromthisMorning]

WOW sharp eye Bryce - I HATE those wire nuts and this is only in there temporarily (it is also taped on) because I did not want to risk shorting out that circuit that will be use for lighting in this bay. Nice catch and you are 100% correct - those wire nuts have no place on any mobile vehicle (I even hate them in the house!).

[@lasangap]

What a brilliant idea. Now you have a Smart Chassis Battery system. Hats off...

[@BeginningfromthisMorning]

Thank you! It has been working very well for us.

[@gregorythomas333]

Excellent idea! And love how you ran out of wall space and went to the ceiling for mounting...way to go 3-D :) Might I suggest you rename your devices (on your phone) to something more recognizable like the new one as "HOUSE TO CHASSIS" or something like that. I have several AC & DC systems, multiple inverters and multiple battery banks as well and had to show my folks how them works just in case. But the names were confusing to them so I renamed them and now they understand it so they can run the systems if I am not available. This recently was useful as we have had two hurricanes come through and they were able to keep essential power running without my input.

[@BeginningfromthisMorning]

Thank you Gregory - we are not going to let a little thing like running out of space stop us! LOL. We actually named this charge controller "Lennard" because it was gifted to us by a good friend of mine (who's name is Lennard). I am currently working on a better system to label everything in that bay (right now they just have some stick on labels that are not a permanent solution). SPOILER: I have learned to 3d design and print stuff! WOW two hurricanes!! Please stay safe out there!

[@basilmccullough3408]

Good evening Juan and family, have a nice day.

[@BeginningfromthisMorning]

Thank you Basil! Have a great day!

[@Schuylker]

Seeing your fantastic projects -and especially the electrical stuff in this bay, it always reminds me of the first few demo videos. I was a little skeptical seeing you tear it down more and more and more and wondering where things would go after you hit the frame. Maybe my skepticism was just a reaction to the humility you two always come across with. You have for sure surpassed all expectations in every area you work through! Nice one, thanks for the vid!

[@BeginningfromthisMorning]

Wow thank you so much - very kind of you to say. Your skepticism was not unwarranted. We had absolutely no idea what we were getting ourselves into! Thankfully with a lot of research and hard work this old bus is shaping up exactly how we envisioned :). Thank you for joining us and encouraging us!

[@DennisWintjes2]

Very cool idea! Thanks for sharing. Like #352

[@BeginningfromthisMorning]

Thank you too

[@rodneymiddleton9624]

What a fancy set up. Looks like you have a well thought out system. Keep us posted on your progress. Can't wait to see your travels.

[@BeginningfromthisMorning]

Thanks! Will do!

[@joseortiz5965]

Awesome

[@MrEdsster]

U d man. Always your videos having adhd it would take me an extremely long time to get a solar system put in my class b. But I'm going to have a person in Panama city do it for me. Thanks again you woke the solar bug up in me again

[@billbelew8275]

Thanks!

[@BeginningfromthisMorning]

Thank you!!

[@brycejeannotte7699]

Very cleaver way to charge your chassis batteries. Great job. Nice to see ferrules being use too. Really keeps everything neat and tidy.

[@briandavis9975]

Brilliant, just brilliant

[@BeginningfromthisMorning]

Thank you Brian - it has been working out just as we had hoped. Starter batteries stay at ~13.5ish Volts and start the coach right up when we need to go :)

[@briandavis9975]

@@BeginningfromthisMorning wonderful I'm doing it on my coach. Again brilliant idea and it makes so much sense. You are my new mentor.

[@allmomomosthomebus3895]

Great idea Juan!

[@BeginningfromthisMorning]

Thank you Larry - little by little she is getting there!

[@olemissjim]

Awesome video!!

[@tabealer]

Genius, good thinking there Juan.

[@BeginningfromthisMorning]

Thank you Todd

[@er1073]

Congratulations that is a sweet charge controller. I just can't get over how organized your electrical bay is it is a mass of wire but so organized and labeled. Thanks for sharing your video with us. Ed

[@laknox88]

God forbid the RV industry in general Gets a Clue!

[@BeginningfromthisMorning]

Thanks Ed I have a few more things I want to do for labeling but we will leave those for another day :)

[@VLBrander]

Wow.. I spent the whole time salivating over your electrical bay. A lot of that you haven't shown. That's amazing. I love it.

[@BeginningfromthisMorning]

Thank you Vicki - one of these days I will make a complete "walk-through" video of our entire electrical system :). We do have playlists of how we built almost every component of the system - but the one thing we are lacking is an overview of how the entire thing works. (Added to the TO-DO list)

[@FirstSuiGeneris]

_Way cool and smart! I like it and thanks for that idea!_

[@BeginningfromthisMorning]

Thank you!

[@steveschannel961]

Excellent idea using a charge controller in that manner. I suppose you could use one to power other 12 or 24 volt items in the bus also.

[@garycleary7191]

This is so simple it's brilliant! Have you shared this with Victron? I'll bet they would put an engineer on this right away to sus out your set-up (might even get a nice attaboy from them).

[@BeginningfromthisMorning]

Thank you Gary - I don't think Victron would endorse this use of their charge controller :). I will say that it has been working very well for us because the charge controller spends 99% of the time just floating.

[@edenfieldwarrior]

Another great project done and dusted. Well done.

[@BeginningfromthisMorning]

Thank you! Cheers!

[@richroj]

looks really good Juan & Michelle. can't wait for the next video!

[@BeginningfromthisMorning]

Thank you Rich!

[@Orbis92]

When I see the buses electrical bay I stop what I doing and watch the video first. I love what you are doing and the bus looks so great from inside and outside so far :) I was going to write half a doctor thesis how the MPPT might or might not be suitable for your application when I realized I know Victron for their regular DC/DC charger systems... I would highly recommend looking for one of those instead using a MPPT charger. Edit: The Orion-Tr48/12-9 should be what you were looking for ;) The thesis :D I'm not sure if you are fine with your charger because its specifically made for solar. The output voltage/current should have a higher priority than the MPPT curve, but I would watch the chargers behavior under different charge levels. I know, you know this, but I will mention it anyways ;) The MPPT algorithm tries to get the most power at its inputs by changing the load current of the solar panel and so the output voltage of the panel (e.g 9V@2A are better than 12V@1A) Based on the price you paid for the charger it should be intelligent enough not to draw the max power from your house battery while figuring out its current maximum power point. I would say you could ask the manufacture if its fine, but I guess they wont recommend this use case just for insurance reasons...

[@BeginningfromthisMorning]

Thank you Orbis - Thank you for the very detailed and thought-out comment. I had similar concerns about the MPPT algorithm trying to pull as much power as it could from a battery bank that is easily capable of delivering over 1600 Amps. Of course, the circuit breaker should prevent this, but this controller has only ever pulled about 3.5 Amps or so and never tripped the 10A circuit breaker it is connected to. This reminds me of a similar concept of "over panelling" in solar applications where some people install more PV Watts than the controller could possibly use because it is quite rare to see 100% throughput from solar panels. The output will always be limited to 15 Amps so the intake will only ever be able to pull maybe 4 Amps from the high voltage side. I looked at the Orion 48/12-9 and 30Amp and they seemed lacking when compared to the MPPT controller. They don't seem to be a multistage lead-acid charger like the MPPT - The documentation seemed to indicate that you set an "output voltage" and that was it - (no bulk, absorption, float phase). It also has a cut-out for when the vehicle is running "hinting" that it might not be smart enough to handle multiple charge sources (something that is handled with the MPPT controller). There is no connectivity options or application to let you see what has been going on with the charger, no access to historical data, etc. One thing that did concern me was if the charge controller being left on 24/7 would consume a lot of power or maybe even possibly over-heat. I know this is not the intended use for this device so of course, Victron is going to say "no do not use it this way". I will keep an eye on it for sure - it has been in and working fine for about 4 weeks at this point without any hint of bad behavior.

[@JerrysThisandThat]

The bus is really coming together and I am looking forward to seeing the adventures you have on the road.

[@osamahasan6326]

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[@normanboyes4983]

Great job - have you updated your ‘as fitted’ electrical schematic?😉😀👍

[@BeginningfromthisMorning]

Thanks, Norman. Not much has changed since we did the original installation, but when we are done building, we will go through and put together final schematics for our electrical and plumbing systems.

[@rickycoon4857]

nice idea awesome execution as always!

[@BeginningfromthisMorning]

Thanks again!

[@bobflinn7529]

Good video and explanation of the need to keep chassis batteries charged from the house batteries and your solar array. The question I have, is what is the phantom draw on the chassis system? Your engine is purely mechanical, so no ECU. Dash radio? You could try pulling each fuse in the chassis system one at a time and monitor the battery drain. SOMETHING is using ~.12kW/a day.

[@BeginningfromthisMorning]

Yes our engine is 100% fully mechanical - however, lead acid batteries will self-discharge fairly rapidly. [from the Internet] "The rate of self-discharge for lead acid batteries depends on the storage or operating temperature. At a temperature of 80 degrees F. a lead acid battery will self-discharge at a rate of approximately 4% a week. A battery with a 125-amp hour rating would self-discharge at a rate of approximately five amps per week." There is some overhead to running the charge controller (I think there is a column in those last screen shots for that). We do have a few VERY small loads on the chassis battery. 2 USB ports up front and the front door (it is controlled by my cell phone).

[@bobflinn7529]

@@BeginningfromthisMorning Thanks for the reply. I have an RV with a mechanical Cummins 5.9 and I've left it for as long as 5 months over winter, with the battery disconnect switch off, come back and it started, no problem. Of course, I'm in Ohio, not Arizona!

[@RussP357]

oh man you are amazing your bus is turning out so nice the wiring so clean you must be in high tech i am loving your build are you done with it or still building. i bought 1964 4106 that im working on love the videos

[@BeginningfromthisMorning]

Thanks, Russ! Welcome to the vintage bus life! Our bus is also a 1964 - #2357 (I think, I don't have the number right in front of me). What number is yours? We are still working on the bus. We will hopefully be finished in the next 2-3 months, and can't wait to hit the road. I am a software engineer by day, but have loved learning all of the skills of building this old bus. Have you joined some of the vintage bus facebook groups? If not, I can give you some suggestions of some great ones to be a part of. The vintage bus folks are fantastic and helpful. Good luck with your bus!

[@PentaxLife]

Great work around I would put in a breaker to stop it form back charging to the mppt when driving form alternator

[@Lake_Lover]

Love the solar video's! Great idea ! Good job as always.

[@BeginningfromthisMorning]

Thank you Mark!

[@without_bounds]

I have a dedicated 100 watt panel and charge controller just for the start battery. Seems to work ok.

[@BeginningfromthisMorning]

Yes this would work fine as well!

[@swaterman08]

I take half credit for saying you could use DC generator without the inverter to a charge controller to the battery. Great idea!

[@BeginningfromthisMorning]

Absolutely!

[@hakunamatataadventurebus5944]

Nicely done sir! I have the same plan for maintaining my chassis batteries.

[@BeginningfromthisMorning]

It has been working very well so far - we will keep you updated if something changes.

[@hakunamatataadventurebus5944]

Hi again Juan. Any news with using the solar charger to maintain the chassis battery? Has it been performing well?

[@pocketchange1951]

👍👌🇨🇦❤, this should work for you, just be sure to have the proper size fuses inline to protect your solar,system or from tour solar bank, Juan , are you able to match your Victron mppt charge controller to your battery specs, as with most batteries, they are have different specs as to what voltage they should be charge at, gr8 video as always, I 7se a si ilar system on mine and has been working flawlessly for years,

[@BeginningfromthisMorning]

Thank you Greg - I do think I will add a fuses to the output. I had incorrectly assumed that the fuse in the unit was for the output.

[@marchalpeck470]

Awesome video as always

[@BeginningfromthisMorning]

Thank you Marchal - I hope you are well.

[@JamesEDennison]

Hi Juan..... I've been kicking this idea around for a while but didn't know if it would work and here you've gone and done it.... great... now I know it works.... I'm also wondering if I could charge a lithium battery bank from the engine this way.... the bus has a 250 amp 24v alternator and I'm thinking of connecting the PV side to the alternator instead of solar panels and then use the mppt controller to charge the battery bank.... you think that would work or am I nuts???... well I already know I'm nuts but thats a separate issue🤪🤪🤪

[@BeginningfromthisMorning]

LOL we are both nuts - that much we have already established! As long as your voltage is high enough to trigger the charge controller (typically 5V above battery voltage) you should be able to make it work!! If you are wanting to run big loads off your inverter I would consider a higher voltage :)

[@jaapdewind8774]

Great thinking. A mppt is in fact a booster and a battery charger in one. Don't worry about cosumption with so many panels |-;

[@BeginningfromthisMorning]

Thank you - it has been working great!

[@ryanchristie5349]

I was looking at AC 120v to DC 12v RV Battery chargers to accomplish this (for me to keep the starter batteries topped off) this is important for me because my lift-gate and rear door actuators are run off of the vehicle starter batteries. This is much more elegant and fits into your overall system architecture.

[@BeginningfromthisMorning]

Thanks Ryan - time will tell if it holds up. I will report back if I see any trouble with it but so far so good :)

[@ryanchristie5349]

@@BeginningfromthisMorning did you change any of the settings to alter or disable the MPPT feature?

[@ryanchristie5349]

...also, I’m guessing that you didn’t connect this controller to your color GX. The GX would add it to your total solar production vs what it’s actually doing.

[@BeginningfromthisMorning]

@@ryanchristie5349 I did not disable the MPPT feature and did not connect it to the color control GX - I am basically using it as a battery charger so my system sees it as a "DC Load". I would say it spends 99% of its time just in "float" mode and draws very little power. However,t we use our starter batteries on occasion for running the macerator pump (~7-10A draw for 20-30 minutes about once every 4-6 weeks). During this time I have checked the MPPT controller and it ramps up to fit that need but settles back down when we drive it back to the storage lot.

[@Grangeno08]

A very good idea. Maybe you want to install a relay (normally close) between your charger and your starter batteries so when you start the vehicle the relay will open the connection and protect your charger from a possible overload.

[@BeginningfromthisMorning]

Thank you Gustavo - the MPPT charge controller should be smart enough to detect other charging devices (shop.pkys.com/multiple-charge-sources)

[@davidmisiluti9069]

Im using a cheap 60a 24v mppt solar controller which is monitored by my 702 BMV its topping up 24v (2 x 12v) truck start batteries. Highest voltage seems to be 28v after a full day of sun. Do you think thats too high and overcharging? After watching this Im thinking of swapping the controller out for the victron equivalent. Also do you use the orion product to charge the house batteries from the alternator? Im running 760ah AGM and wonder if thats something i need to add too. Btw: compliments on your great channel and clean install

[@BeginningfromthisMorning]

Thank you David! 28V does not seem out of line to me. I think float typicially falls back to 13.2 to 13.4 (26.4-26.8 V for 24V system) but "FULL" for lead acid is typically considered 14.2-14.4 (28.4-28.8 V for 24V system). The Victron controllers are pretty nice but if the system you have is serving you well and is working correctly I don't see why you would replace it. I do not charge from the alternator at all - our bank is at 48V and we have not really needed to charge from the alternator.

[@allanhall9656]

What happens to the charge system when you start the engine?

[@TimRebernik]

The current goes one way, so when the voltage rises, the current just stops flowing.

[@BeginningfromthisMorning]

All modern solar controllers are designed to compensate for having multiple charge sources (either a plugin in battery charger, alternator, wind charger, even another solar charge controller). When we start the engine it usually just displays 0W from the solar panels.

[@jamest.5001]

Does it have current limiting? What will happen if the battery gets low, and it tries to pull a ton of current, to charge? Will it pull over 15a, and cook the charge controller? Being its basically connected to a unlimited current source!

[@BeginningfromthisMorning]

It should be smart enough not to do this. This is the entire job of the solar charge controller. If it was wired into solar panels it should work the exact same way. The solar panels can provide up to 200W of power but the charge controller has to be smart enough to limit itself to not over-charge the battery.

[@projecttrawler]

Is this still working well. We have a 24v house bank and want to charge our 12v starter bank

[@BeginningfromthisMorning]

Hi - yes this is still working very well. It has been in since July (about 6 months so far) and not a single complaint. We have put the manual battery charger on our starter batteries since and they are always 13.5 when I check them manually (about once a month - or every time we dump). It is nice to be able to see the history and have Bluetooth connectivity and we never worry about the starter batteries now :). It should work fine with a 24V bank as well.

[@lee8652]

@@BeginningfromthisMorning Glad to see it still working well for ya. I've been taking a strong look at this as well but was concerned when I read that the MPPT 75/15 has a Max. PV short circuit current 15 amps and goes on to say "A PV array with a higher short circuit current may damage the controller" lol our batteries have thousands of amps when shorted so I don't know what to think.

[@ryankidwell9362]

Great idea, and great info on all of your videos and blogs! I’m designing a similar 48v system for my sailboat with a Quattro. Does the MPPT allow you to monitor voltage of your 12v system on your Color Control GX?

[@BeginningfromthisMorning]

Thanks Ryan - I do not have this MPPT connected to my Color Control GX because it does not service my "main" house battery. As you can imagine this is not a "recommended" setup by any means. When we finally get this thing finished I may have to go back and revisit this :)

[@robertdonnelly434]

As ALWAYS, a great explanation of the how's, why's, and what's of an addition to the "Bus"... Does the new MPPT controller default to the FLA battery settings? Or, because it's kinda' a minor thing, did you simply go past that step?? Cheers from Canada, hard by the shores of Georgian Bay, Ontario!!

[@BeginningfromthisMorning]

Thank you Robert - the MPPT Controller is fully programmable but it does default to the 3 phase FLA battery algorithm. If you look closely at @12:02 you will notice on the first day the bar graph shows 3 colors for "bulk", "absorption", and "float" as it went through those stages charging the battery. The rest of the time it just stayed in "float" and really settled in after a while and used very little power.

[@oglaucio]

Pure genius! Well done, guys. As a budget option, could a PWM solar charge controller also be used? Cheers!

[@BeginningfromthisMorning]

Thanks Glaucio! A PWM solar charge controller might work but the efficiency would be absolute garbage. With a PWM controller, you want your input voltage just above but very close to your output voltage. The way the PWM controllers work they basically "cycle" the power (turn it on and off) to get the voltage to drop. What this means in laymen's terms is that to charge the starter battery at 15 Amps we would need to draw 15 amps from our battery bank (not accounting for losses). Since our battery operates at about 55 volts that would mean we are pulling (55V*15Amp) 825Watts to produce (13.5V * 15 Amps) 202 Watts of charging power. The MPPT on the other hand is basically a really fancy DC-to-DC converter so you can see in the video @11:02 that it only pulls about (56.04V * 3.5 Amps) 196 Watts from the battery to charge with 190 Watts (12.81V * 14.80 Amps) of power.

[@oglaucio]

@@BeginningfromthisMorning oh, got it! That makes sense now! I appreciate your explanation. Cheers!

[@mercuryblues226]

you have done a great job very good arrangement except those hoses hang down ,drain them and cut them off. GREAT JOB:

[@BeginningfromthisMorning]

Thank you - those hoses are the original hoses from the heater system that still needs to be used for the defrost system.

[@TheGrimshaw]

What about the bus alternator when you start up, wouldn't the batteries over charge?

[@billbelew8275]

Can you tell me if using the charge controller to charge the Cassie's batteries is still working I did the same thing but my charge controller failed a week later

[@hydroalternation]

having been bus driver for 27+ years the problem begins when the bus engine is running and one of the diodes goes bad on the voltage regulator and an ac spike comes from alternator to high side at about 300 plus amp surge the victron will vaporize i have seen 2/0 cable become a fuse on busses with questionable connectors on the original equipment ie old age

[@BeginningfromthisMorning]

This could certainly happen. I am not sure there is a way to 100% prevent this from happening. All the components are fused or contain a circuit breaker. That much power should pop the circuit almost immediately.

[@LauwersFreddy]

Hi Juan, great video! Just wondering what will happen when you start driving and the battery charges the usual way. Don’t you need a relay to interrupt the solar charging when the motor is running? Thank you for making these videos.

[@1978jra]

Probably nothing, victron just stops charging, when voltage rises enough.

[@LauwersFreddy]

@@1978jra Thanks, you have a good point there!

[@BeginningfromthisMorning]

Thank you Freddy - almost all modern chargers are designed to deal with other charging methods. When we fire up the bus the Watts from solar simply go to zero. We have had this installed for about 4 weeks or so and it has been working exactly as we hoped.

[@nickidewet7711]

Did you make that rivnut tool, or did you buy it like that? Great idea on using the MPPT by the way!

[@BeginningfromthisMorning]

LOL thank you Nicki - I actually broke my "real" rivnut tool and had to run off to harbor freight for this one last minute! It BARELY got the job done but for $10 I am not going to complain too much :)

[@mojo68mitch]

We have the Orion smart converter charger 24/12- 30 basically does the same thing. Never thought of charge controller. Can you wire in a cutout when the engine starts so the alternator takes over.

[@BeginningfromthisMorning]

Thank you Mitch - I looked at the Orion and still chose the charge controller for a few reasons. 1) The Orion looks like you just set a voltage and it converts the voltage - I didn't see the option too set a charging profiles like a lead acid-battery or a lithium battery as is offered by the MPPT charge controller. 2) No bluetooth or historical data logging to let you know what has been happening 3) No need to wire up a cutout for an MPPT controller (shop.pkys.com/multiple-charge-sources) 4) cost. I got this charge controller for about $118 - the 48/12 Orion costs about $215 or so. I only did some surface research on the Orions so some of my assumptions may be off base.

[@markphillips6154]

What do you do for the kids school? Home home school?

[@BeginningfromthisMorning]

Yes. We have always homeschooled them.

[@Bruce-ub8dv]

What kind of 10 gauge wire are you using? All I always find is the 10 gauge solar wire that doesn't have that nice weather cover.

[@BeginningfromthisMorning]

We use marine grade tinned wire. We bit the bullet early on in the build and we use marine grade wire exclusively throughout the entire bus for AC and DC wiring. The cheapest place we could find it was: www.waytekwire.com/products/1461/Marine-Wire-Cable/ - fair warning - it is still very expensive.

[@Bruce-ub8dv]

@@BeginningfromthisMorning Thank you!

[@moritzs3886]

Hi great video. I have been thinking of a solution for dc to dc charging for my bus batteries too. However my house battery aswell as my bus starter battery are both 12v. My idea was to make a circuit that has a boost converter between house battery and mppt which should trigger the mppt with my set voltage and charge starter batteries. If anyone has experience with this, please let me know.

[@BeginningfromthisMorning]

If both of your batteries are at 12V you could use a battery Isolator that is built for this purpose: www.victronenergy.com/battery-isolators-and-combiners/argo-fet-battery-isolators

[@jamest.5001]

I'm interested to see how this works, I have 2battery banks, a12v, and large 24v(7s liion, 29.4v full,)

[@BeginningfromthisMorning]

It has been installed for 4 weeks and it just keeps floating along. I have been checking the batteries to see if I can see any evidence of boiling over or overcharging but it has been all good.

[@richardowens9061]

You have a really state of the art electrical system in your bus! So, let me suggest something that would get you away from lead-acid batteries altogether: Lithium Titanate batteries! The big advantages of Lithium Titanate batteries are that they can be recharged 50,000-100,000 times, they have extremely high demand current capability, they can charge extremely fast, they're as safe as LiFePO4 batteries, a 6S configuration will give you a nominal 13.8 volts DC, and they're very tolerant of low temperatures. The big disadvantage is that they're relatively expensive, compared to both lead-acid and LiFePO4 batteries. But, for your application, I think they would be ideal.

[@sajithaperera1228]

Check his battery installation videos. He has a Nissan leaf battery pack in there. It's providing the 56V for this system

[@richardowens9061]

@@sajithaperera1228 I'm fully aware of his entire electrical system, as I have been watching their series of videos on their bus build for almost three years, now. I'm suggesting that he replace his lead-acid chassis batteries with the LTO batteries because of the advantages they provide over lead-acid, as I listed above.

[@Sylvan_dB]

I've wondered about super-caps for the starter battery. They don't keep a charge like lead-acid (or LTO) but with the 48v bank available, "keeping a charge" doesn't seem needed.

[@richardowens9061]

@@Sylvan_dB Super caps are even more expensive than LTO batteries.

[@Sylvan_dB]

@@richardowens9061 more expensive but you won't need as many. lto aren't great for high current. A $50 supercap module from china will start anything I own (multiple gas and up to 4L diesel). It's 6 of 500F capacitors and about the size of 500g of butter. Probably need 4 or 6 of those modules for that bus.

[@scotthelmann5156]

Why not just have it (your additional solar controller) powered by your solar panels on the roof. Wouldn’t that be more efficient? Don’t forget to add water to your starting batteries as they will probably now use more water.

[@BeginningfromthisMorning]

The solar panels on our roof are too high of voltage (they run at about 170 Volts or so). An MPPT controller with this high of voltage would have cost us significantly more. Great tip on the water - we actually did check it last week and topped them off.

[@JNTimperley]

Have you looked at Nissan leaf or used electric car batteries they're very interesting prospects

[@VLBrander]

Need to go back and look at their battery build.. It's awesome.

[@richardowens9061]

They're using a Nissan Leaf battery pack for their house batteries.

[@laknox88]

Plus 1 extra module. ;-)

[@BeginningfromthisMorning]

Thank you John - we built our battery about 3 years ago and it has been really great. It took a lot of research (this was before we had so much information on them!) but we are really glad we dove in and got a system that has been working great for over 3 years :)

[@Simmons2358]

For every engineering disaster, there is at least one engineer or team of engineers, that was/were shocked that the failure that happened could have happened. Basically, they ignored Murphy's Law. Those look like water lines in your electronics bay! I know, I know, no way they could ever leak.

[@peterg.8245]

They’re coolant lines from the radiator that used to heat the interior of the bus.

[@BeginningfromthisMorning]

As Peter mentioned they are coolant lines that run inside to the defroster for the coach. Yes there is a chance it could leak but there area also high pressure hydraulic lines running to the power steering as well as fuel lines running down the center of the bus that could just as easily leak. I do check these clamps and hoses very frequently ... but there is always a chance ...

[@Simmons2358]

@@BeginningfromthisMorning -- I was sure there was a good reason. May not be able to prevent a leak but to might be able to direct where the fluid goes should there be a leak. Pipe inside a pipe kind of thing. By the, the neatness on you wiring and electronics is impressive.

[@mewky6245]

Your better off using a Victron Orion dc/dc converter,more suited and easier to control

[@randyrainwater983]

👍👍

[@a2cryss]

Since you are coming from a battery source, you probably didn't need to spend extra for a MPPT controller.

[@JerryDLTN]

Do you have a second alternator on your engine to charge your house batteries?

[@richardlazarski4553]

Yes there is an alternator on the engine.

[@peterg.8245]

They don’t yet, several kW of solar in Arizona have been all they needed. I don’t know how far north they plan to roam in the winter but they can charge at a campground.

[@BeginningfromthisMorning]

Thank you Jerry - great question. We have a very robust alternator on the bus (A Delco Remy 50DN rated for something like 275 Amps). We have not hooked it up to charge our house batteries for several reasons. 1) We are trying to be as gentle as we can with this old engine 2) Our house battery operates at 55V and we would need a substantial boosting controller ($$$$) to do that (from 12V). 3) We are hoping between solar, shore power, and maybe an emergency generator we will not need to do this. Of course we reserve the right to change our minds when we actually start using this thing :). We'll see how it goes - we do have a backup plan that involves the alternator if things start leaning in that direction.

[@sellC1964]

No fuse going to batteries on 12volt side?

[@BeginningfromthisMorning]

I had originally thought the 20Amp fuse on the unit was for this ... I have read more and it is not for that! So I will be adding a 20A fuse to the output.

[@dannyjensen4954]

I don’t think this was a good idea when I looked at it.. I had this idea a few years ago. Per the link below... Please don't ignore that the MPPT charger can short the PV input. If it does that when connected to a battery, bad things may happen. See Error codes 38 and 39 for some situations that can cause it: www.victronenergy.com/live/mppt-error-codes . Source community.victronenergy.com/comments/57064/view.html. Also a guy Rene on a FB group called Victron and asked them if this was okay and they said something like the MPPT could burn out being under load for an extended period of time. I can’t find the post. You could call them I guess but this does seem to work! Thanks for this video.

[@nebulight]

This. Normally the mppt will wake up in the morning with sunlight but this is running non stop. And if it ever attempts to short the panels this won’t be good.

[@dannyjensen4954]

@@nebulight thanks for your comment validating my impression of why this may not work out so well in the long term.

[@adon8672]

Since the higher voltage battery being used as solar panels is much larger than the battery being charged and since the battery being charged is not always in continuous use, don't you think the mppt charge controller will be idle most of the time?

[@dannyjensen4954]

ad on I am not an expert. I’m not sure the voltage difference matters as much as watts. It would seem if the SOC of the starting battery is mostly high, the amp output should be low when floating. Perhaps limiting the charge state timers could further reduce load. learning more about when / if the mppt shorts the panel input would be critical for me since I am on a boat and can’t easily retreat from a battery explosion.

[@BeginningfromthisMorning]

Thanks guys - great discussion. I am still learning about this stuff and I find all this stuff pretty fascinating. Here was my thinking: Does the solar charge controller care/know that the power is coming from a battery? At its most basic level doesn't a solar panel act like a really poorly behaved battery? It seems that an MPPT controller is really just a fancy DC-to-DC converter. Under normal circumstances (using solar panels) if my battery is full at 10AM and I still have 6 solid hours of sunshine putting power into my panels shouldn't the charge controller just use enough power to float my batteries - limiting the current to just trickle charge the battery even though much more power is "available"? I looked up Err 38, 39 and they talk about another source charging the battery at a very high voltage (referring to an an equalise cycle at something like 17 Volts) or the battery being disconnected using a manual switch. I have had this installed and working for about 4 weeks - I have not seen any errors yet. For the first couple of weeks I kept a very close eye on the batteries looking for any evidence of boiling over and checking the voltage with my multimeter to be sure everything was OK. I was concerned with the 24/7 operation that might over tax the unit and cause it to fail. However, if you check out the historical data (see the last screenshot) shows that almost all the time this is "float" or "idle" and is consuming very little power. We do not use our starter batteries for any 12 loads (those are handled with buck converters off our 48V battery).

[@lutomson3496]

Only works in the sun though why not install something like a Trik-L-Start that keeps your chassis battery charged when plugged in during storage..I keep my rig under cover and covered great videos though

[@JNTimperley]

Hello have you looked at battleborn batteries for their warranty and capabilities?

[@richardowens9061]

Battleborn batteries are great! But, they lack the demand current capacity to function as starter batteries and they're not cold temperature tolerant. Their Nissan Leaf batteries will serve their needs well for their house batteries. So, I would suggest they consider Lithium Titanate (LTO) batteries to replace their lead-acid chassis batteries.

[@allmomomosthomebus3895]

The storage they have would have cost like $14 or $15k or more as battleborn batteries. He has a huge battery capacity on this bus.

[@BeginningfromthisMorning]

Yes the Battleborn batteries are a great product if you are looking for a drop-in "no mess", "no homework needed" replacement for a lead acid system. In our particular situation I think they would have offered some pretty substantial down-sides. The obvious one is Cost - we have the capacity of about 18-20 or so battle born batteries - that alone would have cost more than our entire system (including solar and wiring). Another downside is that Battleborn does not really like you to use their batteries in a 48V configuration. Since the BMS in each battery does not communicate with the outside world it has no way of knowing what the other cells are doing or how charged/discharged they are. The Warranty is great but in less than 10 years there will be something even better/lighter/cheaper. even TODAY - I would go with 280Ah LFP cells - 27 kWh costs about $3000 shipped to your door. For the price of 3 or 4 battle born batteries you get the capacity of about 22 of them. so at about 1/7th the price if they last even 2 years you are ahead. (This is very similar math to what I used with the Nissan Leaf cells I am using - they cost me about $2800 - so even if they just last 2 years I am ahead already)

[@allmomomosthomebus3895]

@@BeginningfromthisMorning Juan tell me more about the LFP cells... this is the first I'm hearing about those...

[@BeginningfromthisMorning]

@@allmomomosthomebus3895 The batteries I am talking about are 280 Ah LFP batteries. Here is a link for them: www.alibaba.com/product-detail/3-2V-280Ah-Batteries-Cell-prismatic_62556226025.html?spm=a2700.galleryofferlist.normal_offer.d_title.34a62f3c6oKpNW you need four of them to make a 12V "battery" or 16 to make a 48V "battery" - More work than a drop-in battery but just as safe and. you can use an external BMS that actually communicates with your system.