Making 12 volts from my 48 volt battery, DIY Powerwall

I install a step-down converter into my DIY Powerwall. This will convert the higher voltage of the battery (48v) down to 12 volts so I can run smaller things. The first thing to run are the 12v computer fans to cool the cabinet. I bought this step-down converter from amazon, link below.
This dc to dc converter is part of my larger project of making a solar off-grid system. (sometimes called a buck converter)
Step-down converter: amzn.to/2y6WMoO
12v Fuse Block: amzn.to/2t5AaiC

[@MStrickkk]

Excellent choice of fans. I have about 20 Arctic fans running right now. Spend the extra buck and get the ball bearing fans every time, you'll never be upset.

[@seanpeacock8959]

I like that little step down that you have. I was thinking about using that on my 48 V batteries for my ham radio. I think there is a DC the DC step down that’s adjustable out there you can get a little more power out of it.

[@TeamRiceUSA]

Nice battery bank and solar water system. One other way to increase efficiency of solar water system. Only if your system can handle salt added to water would increase denisity of medium.

[@glenngoodale1709]

I love your videos, they are inspiring and calming, please keep up this quality!

[@DavidPozEnergy]

Thanks.

[@alexshatner3907]

@@DavidPozEnergy Dose the step down converter drain the 48 Volt battery by just keeping it connected? even when the converter is not in use? just curious

[@katgarvey9301]

Hahaha, I love that lawn boy cut scene.

[@SuperFredAZ]

You should put some heat sink grease between the case and the iron, but you would be better off with aluminum or copper and more area, if you are concerned.

[@dwfdwf5371]

Cool the batteries are awesome.

[@todisboss23]

I love what your doing, but you need a BMS these batteries are lithium cobalt (which is the most unsafe) even if one of the cells comes out of balance it could lead to your whole garage burning down. These aren’t lead acid batteries and they aren’t made to be treated like lead acid batteries. They need to be managed with a lot more care or they will catch fire. Personally I would not even use these batteries until I got a bms for them. Thank you and have a nice day

[@DavidPozEnergy]

Thanks. I'm still looking into different BMS's and trying to decide on which one to get. I'll need 8 of them for my current set-up.

[@moriwaki80]

I've been using 2015 Chevy Volt modules on my scooter conversion and they have kept their balance for 6 months without any issue. I just charge and discharge with a buffer and do a monthly check. This means 4.07v max charge per cell and max 3.55v per cell discharge. I just checked today and they are just the same as when installed.

[@DavidPozEnergy]

Nipping Shrew de Reefs: Thanks for sharing your success. It is very encouraging. Mark Osborne also has no BMS and shared his success in this video: kzbin.info/www/bejne/mpOyZZeen6p5q5o

[@moriwaki80]

cheers! Yes I had thought about it for a while, but read of others not having issues. I also limit to 320A max discharge to avoid stressing them and potentially causing them to drift. I think peak 10 second discharge is 350A.

[@moriwaki80]

Also when I was using GBS lithium iron phosphate cells they would drift quite quickly. I was using a BMS but found it couldn't cope with the amount of variation between cells as the bleed off on the resistors wasn't enough to prevent the cells first to top up from over charging. So with these I also charged within the BMS limits and discharged within the limits, but needed to check cell variation every 2 - 3 weeks.

[@harveyboy45]

The guy below knows what he's talking about. My batteries exploded in my front living room took them outside and my entire bike caught fire the fire brigade had to be called. Have water available as powder or electric carbon dioxide will not put a fire out on these batteries.

[@Dutch_off_grid_homesteading]

heya nice small stepdown converter

[@DavidPozEnergy]

No, It was bad. Don't buy it. I removed it.

[@Dutch_off_grid_homesteading]

@@DavidPozEnergy ah oke thank now I won't buy it

[@jackturtle131]

that looks like an Honda motorbike gadget

[@Paul_Bearden]

I put two in parallel, now it can do 400 watts, but it still gets hot, so I added a fan.

[@timcannady3213]

Dumb question for someone new to this. Why did we add the fuse/breaker upstream from the converter? Is it inherently needed as-is? Or instead, maybe something related to plans you have for using the 12v power? I ask because I’m about to use this same converter on my 48v ebike battery to power some 12v lights. I considered adding a fuse for good measure. However the batter itself has. 40a fuse, so I thought I might be good there? I *am* new to this though, so seeing you add one grabbed my attention.

[@DavidPozEnergy]

Hi Tim, The additional fuse is probably not needed, but I had a spare fuse holder. BTW, I've removed this converter from my setup because it get's HOT all the time. It constantly draws power even if no load is on it. I mention this simply so you may want a switch between the battery and converter so if you don't need lights you can turn it off.

[@timcannady3213]

DavidPoz Thanks for the follow-up as well as the tip for the switch! That hadn’t crossed my mind until today coincidentally. Another video of a similar controller has a switch for similar reasons. Will pick one up. On a separate note, might there be a better ready-to-go solution than that one to achieve the same thing? E.G. from a different company? Or maybe it’s inherent in the technology?

[@DavidPozEnergy]

Hi Tim, I don't know of another DC to DC converter that does not waste energy. You may already have thought this through, but could you add a small 12v battery just for your lights? I've never built an E-Bike, but are you going to have 40 watts or so of lights? If the longest you could ride your bike is 2 hours, then 80 watt hours of power, plus battery loss. Maybe 110 watt hours of battery size at 12v, 9.2 amp hours. www.amazon.com/Phosphate-Rechargeable-Batteries-Baseline-Battery/dp/B01FVMQJCY/ref=sr_1_2_sspa?keywords=lifepo4&qid=1563665505&s=gateway&sr=8-2-spons&psc=1 Set these up as 2p4s and have a nice 12v battery. Would that not be simpler than doing a conversion? I'm sincerly asking because, like I said, I have not built one.

[@harveyboy45]

I've never heard of a single system that can balance cells properly

[@mark_osborne]

I'd love to know the topography of that converter - it's got to go something like this: DC input > Oscillator > AC > voltage regulator > step down transformer > rectifier > output It would be fun to put a scope on the output.... if my topography is true, it must have some ripple. What are your thoughts . Nice video David

[@leegenix]

I'm sure it uses some good capacitors in that device. I had a Yamaha DX7 synthesizer. I looked inside and there were about a dozen toroid induction coils in there. Being all digital, the voltage logic levels had to be ultra clean when I saw it on the friends oscilloscope.

[@thedampestcrib6004]

Did you make or buy the bus bar? Useing 100ah batteries so I'm assuming bus bar needs to accommodate 100ah per series so 4 series 400amps?

[@DavidPozEnergy]

This is an old video series. At the time, I used scrap metal I had on hand. I used some aluminum angle that was 1/4" thick. I have a more recent video on busbar that may be helpful: kzbin.info/www/bejne/m4jUe52ifdSKb6Msi=mHbFM6KH_S0yd8yj

[@mark_osborne]

I'd love to know the topography of that converter - I'm thinking something like this: DC input > Oscillator > AC > voltage regulator > step down transformer > rectifier > DC output It would be fun to put a scope on the output.... if my topography is true, it must have some ripple. What are your thoughts .

[@DavidPozEnergy]

I don't have a scope to test it, otherwise I would. BTW, I linked to your video for Tod Isboss in the comments below.

[@mark_osborne]

which reminds me , I've got to do an update video on the current state of "un-balance" on my poor battery packs after 18 months.. my gosh I don't know what I'm gonna do :P

[@DavidPozEnergy]

I hope you do, I would love to see that.

[@SuperBrainAK]

it is probably a syncronous buck converter, those tend to draw power when idle but will be 90-95% efficient at full load

[@michaelmourek3879]

Your inverter can run on 14 volts - therefore your inverter will always stay on -:your converter get HOT it can explode - true

[@HaroldMcDermott]

So if it heating up that quickly it must be wasting alot of energy, but would probably use alot less energy going though the power inverter itself.

[@12headlock]

Yeah I agree heat means a lot of energy... I want somone to help me... If you put 4 12v batteries in series and just take 12v off one battery do they all discharge together... Because this would mean you would have the most efficient 48 and 12v supply without any loss... No1 wants to answer my question though

[@theMekanik]

How many amps kan you push through a 48 volt to 12 volt step down konverter

[@DiyintheGhetto]

Hello David why not use a Din rail breaker for your 48v and one for 12v stuff? You can add as many breakers as you like. And i have been seeing them all over the internet for good prices. I have picked up a 24v DC breaker with 6 amps for a small project I'm doing. It was 13 dollars for the breaker that is a little high for me because I'm cheap but i need to to keep my stuff safe.

[@DavidPozEnergy]

I plan to do just that. I'm planning to add breakers for the batteries, inverter, dc-converter, and one for the charge controller.

[@DiyintheGhetto]

DavidPoz Nice. I we can't wait to see that.

[@jdell6250]

Other then small fans, what other devices can one run off this 12v setup?

[@toysareforboys1]

The step down converter you're using can run right down to 30v input while still spitting out a perfect 12v, that's how step down converters work. If I'm running a 12v device right off a panel I use this step up/down converter if running a small panel (8v to 40v input, 12v/120watts out, www.aliexpress.com/item/8-40V-to-12V-10A-8-40V-TO-12V-10AMP-DC-DC-Converter-Reducer-Regulator-Waterproof/32690762976.html ) or I use this step down converter on large panels (18v to 40v input, 12v/480 watts out, www.aliexpress.com/item/24V-TO-12V-40A-DC-DC-Step-Down-Converter-Reducer-B40-24-12-Daygreen-CE-Certificated/32822253858.html ). They also have the same ones that put out 13.8v if you'd like charge a lead acid battery plus run your load at 13.8v. I love that you bolted the circuit breaker right to the buss bar, I do it similarly with fuses in my car: ecuflashking.com/junk_in_the_trunk.jpg :)

[@theMekanik]

Why don't they just make 48 volt DS applianses???????????????????????

[@bobbyjunelive1993]

I have two choices. Buy a 12v 100ah battery later or use my 48v 20ah battery now. I'll be running with the 12v and inverter for two iPads, a macbook, some iPhone and some fans. what would I be loosing if i choose what I have?

[@1012magdi]

Can it power my 12VDC 2Amp router 24/7 - how hot is it ? warm or hot ?

[@GCSol]

David, how is the buck converter holding up? I'm thinking about getting one but have been seeing mixed reviews on it.

[@DavidPozEnergy]

The buck converter still works, but I removed it. it gets hot. I'm using a 12v lead acid battery to run my cooling fans and top off the lead acid battery every few weeks. Not as elegant as I would have liked. At some point I will figure out something else. Maybe I'll use the same buck converter, but add a relay to switch it on/off on the 48 volt side when not needed. Again, it was just HOT all the time. I even tried adding aluminum stand-offs but it wastes a lot of energy as heat.

[@GCSol]

@@DavidPozEnergy Thanks for the quick response. I was wondering if your angle iron helped with the heat. I've read several reviews where people say it draws power even when not being used and it gets very hot.

[@GCSol]

@@DavidPozEnergy David, I've been using this converter for six weeks now. I've been checking it everyday and it hasn't gone over 110 degrees. This may be better than what you were experiencing. www.amazon.com/gp/product/B079Q2QPGW/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&psc=1

[@DavidPozEnergy]

That looks like a very nice unit. Yes, that is much lower temp than I was seeing. Have you been able to measure the efficiency under load, and the idle watts? I'd love to know.

[@GCSol]

@@DavidPozEnergy I'm using it to run several LED lights and cooling fans. At idle it uses 3.6 watts at 97 degrees. When everything is running, the wattage is equal to the stated wattage of each device. I did mess around with it and got it up to a 20 amp draw at 110 degrees. I haven't used it to it's full 30 amp capability so I'm not sure how hot it will get at that point. What kind of temps were you getting?

[@stephenbramble]

still wanting to know were you bought the panels

[@DavidPozEnergy]

Hi Stephen, I checked with my POC, and he asked me not to post his info online. Sorry.

[@ElaBellll]

Ebay or amazon, search for X volt stepdown and you will find lots of different types.

[@rickyfinch9671]

How to drop 54.6 voltage to 12 let me know thanks

[@NathanShantz]

Great video! I want to use a 48v to 12v step down converter for and EV ATV project to run the lights. It's suggested amps is 10A so I was going to put a 10A car fuse in but most fuses are rated to only 32V. Did you have any problems with your fuse and is yours rated for 48V? Thanks!

[@DavidPozEnergy]

This particular converter was always hot. It drew power even with nothing attached. So I removed it for now. I have also replaced my first fuses with some class T fuses that go up to 120 volts DC. I didn't have a problem with the first fuses, but I wanted to play it safer.

[@igorberezin856]

All 120v fuse can be used all the way down to 1v projects since only current is what matters not voltage when it comes to a fuse as long as its not higher voltage than rated om the fuse

[@johntatman9168]

Did you have any trouble with arking when you connected the input leads to the bus bars? I'm getting a major ark as if there is a dead short in the converter.

[@DavidPozEnergy]

No, but this unit did get very hot. I removed it.

[@johntatman9168]

@@DavidPozEnergy What did you end up going with?

[@davidaustin4579]

I know this post was years ago but I have a question.... I'm going to install the same converter on my 36v golf cart that I just went with a lithium boxed set up and it has no post. It uses a plugged in cord with ring eyelets. Back to the converter, you didn't attach the black neg coming out of the converter. I was going to attach mine to the neg. block I have created witch has all the battery neg wiring attached. This is also were the converters input black will be. Is that wrong?? Hopefully I didn't lose you! There is no 12v accessories black wire only a power feed to a fuse bus for horn, lights, etc. That is the original set up. Feeding that prior with old lead batteries (hooked to only 2 - 6v ones) is only one wire, no neg.

[@DavidPozEnergy]

I would not buy this particular converter. It was very inefficient, always too hot. I removed it. If you are doing a golf cart, try this one instead: amzn.to/3e4HTWQ

[@redman2751]

Have you thought about running DC voltage lighting in the garage instead of converting dc to ac and then back to dc again for LED lighting.

[@DavidPozEnergy]

Hi Jared, Yes, I have thought about that. I bought some LED ribbons that run on 12v and hooked them up to test. They were very dim compared to these and when I calculated out how much it would cost to buy enough to get comparable lumens it became cost prohibitive.

[@redman2751]

DavidPoz what about RV light fixtures or the trucking industry lighting? They are generally designed for area lighting versus ribbons lights which are more accent lighting.

[@DavidPozEnergy]

Hi Jared, It might work, I don't know. Another way about it is to buy 12vDC light bulbs, that screw into a normal fixture and wire in fixtures dedicated to the 12vDC power source. These options might work. It would be a lot of fun to test them out. I guess it comes down to what you are saving. If the average inverter is 90% efficient, then you are saving the 10% loss. If I turn on every light bulb inside my house I'm at 168 watts, which means if that was being powered by an inverter there would be around 19 watts of energy wasted in the conversion process. You could try running the math out further, but paying extra for DC lighting is probably not worth the savings. But I admit that I'm just using a gut feel here. What do you think?

[@redman2751]

DavidPoz I agree, I haven’t done the math at all. I’m in the early stages of wiring a garage similar to yours(with a battery bank and inverter) was just thinking about running a 12vdc setup for lighting and run the inverter for all the other AC appliances. Not sure how feasible this would be but I’ve been following you for awhile and was wondering if you had tinkered with the idea at all.

[@DavidPozEnergy]

Cool. I've made a story board for a video that is specific to workshop lighting, but have not yet filmed it. I was going to focus on Lumens and lux, but I might address this question in that video. Do you think that would be good?

[@user-cr6ki4qs4y]

Hi David. How did u test to know that device was using 3 watts? Does that 3 watts increase as you draw more power?

[@arjuns6480]

How much money this parts cost

[@DamonMedekMusic]

I have a bus conversion with a 48V 50Ah Battery system. I'm wondering if my bus batteries die. Can I use a 48v to 12v 20amp step down converter to charge the batteries? That should bring the battery up to 12v and start charging the amperage. It will take awhile but then if I disconnect the step down converter. The batteries should be strong enough to start it up. Is that right? My starter pulls 200 amps so completely removing the acid lead batteries would be a bad idea a basic step down converter wouldn't handle that. I'm asking in case I'm ever in that situation.

[@DavidPozEnergy]

Yes, that sounds like it would work well. I've seen people do that.

[@ludlow7369]

Okay so the heat from the step-down converter is energy loss/waste. Does anybody know of a way to step down from 24v to 12v w/o such wasted energy?

[@fernandocacnio2634]

How to charge 12v Battery by DC generator motor?

[@cathyrobinson885]

David, I'm trying to solve an off-grid power problem. Components include a 48 to 12 volt MagneTek converter charger and a 12 volt LP fridge RM2652; the 48 volt to 120 Xantrax SW4048 ac inverter stays on and will not go to standby. The fridge looks like it draws 12 volts at 12 amps when calling for cooling. I'm considering the Cllena 48 step-down 12 v 20 amp converter, the spec shows low no-load current to reduce idle power draw. Thoughts? Hope you have some suggestions for me. thanks Cathy

[@DavidPozEnergy]

I had bad luck with my Celena, it was drawing a lot of power even with nothing loading it. I trust Victron products a lot more. Here is an example: www.invertersupply.com/index.php?main_page=product_info&products_id=24883&gclid=CjwKCAiAg9rxBRADEiwAxKDTujG_O-Kksg4dLHzqA0QinUWg5m8T-OX0SXGFbRKZ-2hbOLWGxn-nKhoC8D4QAvD_BwE This can be used direct to your fridge from your 48v battery. It outputs the 48v. It's possible your setup doesn't work if your fridge has a larger inrush current draw when it first starts. Your 48-12v converter might not be able to handle that. If this is the case, then a small 12v battery (buffer) between converter and fridge might handle the surges. Another option would be to change out your fridge for a normal 120v AC fridge that can run on the inverter. Another option: Set up a mini solar off-grid system with a small 12v battery, charge controller and solar panel. This can be done with a MPPT charge controller like: amzn.to/2GMGtir “As an Amazon Associate I earn from qualifying purchases.”

[@starckmad1779]

First! Good job David.

[@jamest.5001]

Do you have a link for the buck converter? I want to buck my 29.4 / 24v system to 12.5v or so. I know the 48v version will not work with 24. But I'm interested in the brand and where you got it. I have a large'ish 8-12 amp china made buck. And a few 3amp buck converters. I'm thinking I will either use them on led lighting or a few other things like usb jacks . and 3v for my water heater ignition. Its an camping style tankless gas . it takes batteries. I don't want to have to replace them so I guess a small buck converter and a capacitor to help with current surges on start. Since its a small buck converter. Isn't it amazing the power in such a small lite cell. Lithium is awesome! I have 108ah and building. I'm adding about 30ah soon as they get here! I hope I got enough sun for 1200watts of pv to charge the bank . I can add 300watts or so without buying a charge controller. I loose sun about 4 in the evening. So I plan to have 2-3kw in pv. And over 1000 ah in lithium batt bank. To run my off grid home. I don't mind using my generator for laundry day. And use a gas stove and grill. Can't wait to see more of your setup! Keep at it! Sorry for the rambling!

[@DavidPozEnergy]

Here is the link: amzn.to/2y6WMoO

[@leegenix]

There are lots of 3.7 VDC Lithium Ion batteries out there. That might work?

[@whynot8416]

I'm not good with electricity in the slightist so could someone help me out. I have a 48v lithium battery that's rechargeable. Will this work to get a 12v and 3amp output?

[@DavidPozEnergy]

Yes, it can work. You could probably even use a smaller model.

[@Bob-uw1zn]

I have a project for you. I acquired a 48 volt 17 amp hour ebike battery which I have no use for, unless I can convert it to run a 1500 watt 12 volt power inverter. But considering I don't know anything about electronics, is it possible and what connectors do I need to make it all work together?

[@DavidPozEnergy]

I don't know of any DC converters big enough. You would need about a 150 amp converter. It might be easier to get a new battery.

[@OffGridSolar]

Hi David, Did you ever find a new 48 volt to 12 volt step down converter? If you did can you make a recommendation or provide a link?

[@dznuttzonyachin7499]

Efficiency of step down ?

[@DavidPozEnergy]

This thing was getting very hot all the time. Even with no load. Don't buy this model.

[@kevindooso4988]

Hey, Any recommendations for the dc to dc step-down converter 48v-12v?

[@DavidPozEnergy]

Not this one! I like the Victron brand ones the most.

[@szwengao4839]

Hello Kevin, We design and manufacture dc/dc converters.

[@micjakes1]

Need to ask your help Dave, i am putting a 48volt system in my van. Can i run a cable from the car battery using a 140 amp isolator and a 12v to 48v step up to charge the 48volt batteries? Thanks

[@DavidPozEnergy]

Yes, but you need to make sure the 12 to 48v boost converter is CC/CV, meaning constant current and constant voltage. I have not found one that will go 12 to 48, but I have seen them 12 to 24 or 24 to 48. Although I'm not building out a van so i haven't done an exhaustive search. Do you have a link to the products you are looking at?

[@micjakes1]

@@DavidPozEnergy Maybe the : www.amazon.com/Dual-Battery-Smart-Isolator-KeyLine/dp/B00WTAFR84/ref=sr_1_1_sspa?crid=28MKNB6KEDHCB&dchild=1&keywords=battery+isolator&qid=1585368574&sprefix=battery+iso%2Caps%2C243&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExMDJBQTVWVTlYQk5UJmVuY3J5cHRlZElkPUEwNDYxMDM5MjJLWFBWNEE4UU9GQiZlbmNyeXB0ZWRBZElkPUEwODM3NTkxMUVJUUlMVDZKMlo3TyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU= for the isolator and www.amazon.com/SMAKN%C2%AE-Waterproof-Converter-10-30V-Supply/dp/B017TPRLLY/ref=sr_1_3?dchild=1&keywords=12+to+48v+step+up+converter&qid=1585368424&sr=8-3 for the step up transformer.

[@DavidPozEnergy]

Hi. That isolator can work on older vehicles, but sometimes newer cars have alternators that can throttle back (lower voltage) when not needed, which might cause this to shut off. But if you know your vehicle stays 13.3 volts whenever it's on, then yes, that isolator can work. The power supply module can not be used to charge lithium batteries. It is not a CC/CV charger.

[@kevinclark2856]

here is one for you lol am old just fixed alternator on my car witch was a bastard pain now it is kicking out 17.4v is there a thing can put betweet terminal to redues to 13v as i am sick to death off in lol some sort dial thing ? kev uk

[@jameswilsin5348]

Can you use that stempdown on a 48 volt panel to hookup to a 12 volt controler

[@DavidPozEnergy]

I don't know if it will work or not. I've never tried.

[@seriouszen5670]

What is the maximum amp for the output!?

[@psychicmind9]

is there power loss once you do step down from 48v to 12v ?

[@DavidPozEnergy]

Yes. I don't think this particular one if very efficient. I took it out of service because it was always hot.

[@psychicmind9]

@@DavidPozEnergy Thank you for your respond. Really appreciate it.

[@robertpolito6139]

Battery hook up sell a lawn mower batteries like that one for $6-.

[@VroomvroomNY]

Where did you learn all of this?????

[@DavidPozEnergy]

LOL, I'm still learning. It started with books on solar, then forums, then KZbin. One of my favorite resources are the videos from "Alt-E". They are my single favorite source of information. www.altestore.com/video/

[@banglarphoto9565]

I have a thousand watt powder inverter in my bar bolt, four batteries of the bar bolt, one battery one hundred and fifty watts. I will run a cylindrical machine. Would you like to say my answerHelp me

[@rcmedianetworks1920]

I need this can you please help me for that

[@DavidPozEnergy]

Sure, here is the link to the size I bought: amzn.to/2ORFK11

[@IceAge20017]

I bought one of those converers. Piece of crap. The output wires were short circuited inside the silicon.

[@DavidPozEnergy]

Yeah, mine was getting very hot. Burned my fingers, so I removed it.

[@ryans5565]

electrical tape is a NO NO

[@danagrauke5761]

Are 😂using ion batteries

[@rogerkerkmann]

12.2 V sucks, can't even float a battery. Adjustable? Mabe a cheap solar controller that's adjustable. Thoughts? Also to all the BMS trolls, lots of inverters have high and low cutouts already, a voltmeter is a good thing, even better get one of those RC voltmeters that do up to 8 cells with low voltage alarm, $5 bucks on E-bay, walk by and see voltage flash on each cell? Thoughts?

[@DavidPozEnergy]

Hi Roger, Yeah, 12.2v can't float a battery, and at 240 watts I can't do much with it. However, I bought this to run the computer fans to cool the battery cabinet. I think it will work fine for that job. I was worried that it would only put out something like 10v when I have 43v input, but was pleased it at least hit 12v. As for the BMS... I agree that it would be great to visually see the voltages of each cell. That has been my hang-up on most of the BMS boards I've been seeing; no interface. I think it would be very cool to hook up an Arduino that could display all 96 cells at once!

[@jrgt628]

Roger Kerkmann yes you're right it can be run without a BMS but it's not advisable the BMS does many things to support those batteries. The engineers that GM spent many man-hours figuring out all kinds of safety and protections related to the batterys. So now this gentleman had to repurpose these batteries with no form of Fail-Safe or disconnect. And you're suggested to him to go on eBay and buy a $5 product so that he can monitor the batteries. This is what a BMS system does it's a Fail-Safe if there's a problem. Running these batteries long-term without a BMS system is not advisable. I work in aviation, and these batteries are currently being used and I can tell you not using a BMS system is an accident waiting to happen.

[@ahaveland]

Roger, Lead acid cells balance themselves. Lithium cells don't. Really bad things can happen without using a BMS. You may get away with it for a while, but I guess it depends on how much you value your battery, your property and the lives of your family and the risk you're willing to accept. Your choice.

[@DavidPozEnergy]

Hi Andy, I've seen some BMS boards on ali-express in the $30 range. I have 8 batteries, so $30x8=$240, which is much more doable. Can you shed any light on these style boards? Near as I can tell, they don't have a user-interface. Are they good otherwise?

[@rogerkerkmann]

Soooo if you have 5 cells in a pack in series, even a bms doesn't check every cell!! Unless you got a hundred bms. If you have big prismatic cells it's easy, my point with the rc volt and alarm you can monitor 8 cells for $3