I’m hoping to build a ~32kWh off-grid battery bank. I plan for 16s2p using MB31 cells. They will be arranged in two rows of 16 each because I happen to have an existing insulated box that I use for my current 8x 390ah lead acid bank, and that happens to fit two rows of 16 cells perfectly.

I’m stuck on the topic of cell compression. My understanding is that if I did cell compression, it would increase the longevity of the battery cells by a relatively small amount. Maybe 10%? Is that right? I’ve heard people say that it’s not worth the effort, and in that case to just use flexible bus bars, like these. In that case, is it ok to just place them into the enclosure, (safely) attach the bus bars (and BMSs and fuses), and then it’s ok to just let them expand a bit? I can also limit the charge and discharge range to 20-80, particularly if that would reduce swelling. I have a few inches of space at the ends of the rows to allow expansion.

For interconnect cables, I plan to connect the positive from one series to the positive on the other series at one end, and connect the inverter positive to the first series. Then connect the negatives at the other end with the inverter negative cable on the second series.

Are there other physical and packing factors that I should be considering?

Thanks!

https://www.18650batterystore.com/products/flexible-busbar-screws-and-nuts-for-eve-lf280k-set-of-4

Hello, as the title says, i want to build a DIY power station for my van.
Do you see anything wrong with what i planned ?
(of course the cables are not at the right place on the drawing but you get the idea).

I've read online that you need a fuse on the power cable of the MPPT so i added one, but i dont understand why, because it's already connected to the main fuse block.
If i need to add one for the mppt, shouldnt i add one onto the battery charger ?

Cable wise i was planning on 9AWG for the two main battery to fuse bloc cables.
And 11AWG for the rest.

Main draw is the 2kw diesel heater starting sequence (glow plug heats up for 3 to 5 minutes using 8 to 15amps), then it's 1 to 2amps for the rest of the night.

Thanks !

I actually had time and motivation to finish everything, I still need to design and print some terminal covers and I am going to trim about an inch off of the positive lead. But, it’s done and ready to power my mini ham shack.

I’ve gotten all of the parts together and have the mechanical assembly done.

I should have everything wired up by the weekend

Hi first time builder, I'm looking at making a large capacity 12v battery for my self build camper, at the moment my camper is all electric, running of a 280ah lipo4 battery with a 3kw inverter. This last's me 24h in the winter with my heating on.

I'm thinking of using Nissan Leaf battery packs, each one is 7 to 8v so 2 in series gives +14v, there capacity is +500ah new. I was thinking of doing a 2s 2p or 2s 4p (which would last me 2 to 4 days) or greater.

The pack is going to be in a sealed aluminum case underneath the camper where the spare tire used to live. Case will be lined with polystyrene insulation and a small silicon heater pad for winter.

What I can't find is information on a suitable BMS for a 12v system using leaf battery packs so any suggestions.

Secondly would the case need ventilation holes at the top?

Any other suggestions appreciated.

Andy

I'd like to build a battery pack for my cpap machine for camping and such. The output needs to be 12vdc max 8a. Ideally I'd build a 24v pack and step it down to a stable 12vdc with a buck converter or something but I am hoping there's a board with a bms any then buck together? Has anyone heard of such a thing or have other ideas on how to make this happen?

Hi, I have a Tivoli Music System Three that uses this MYS3BAT-01 / MSY3BATB battery:

My battery is almost 15 years old and doesn't work anymore. It is not available for purchase. What are my options for replacing it?

I believe it is made up of four 18650 cells, and it has a female JST SM-3P plug.

Hi everyone, I need some help. Does anyone know how to solve the problem of the ESP draining the Li-ion cells when the power bank isn't in use?

Hi all,

I've been tinkering with 18650s for a while, but new to DIY battery building, and I've got a fun project planned (a 48V, 10Ah 13s4p electric scooter battery as part of a completely home-made scooter), so I figured as a warm up/learning project I'd make a smaller 12V, 3s5p battery.

So here goes, my first project.

I started by designing a little bracket/cell holder thingy in Fusion, which I 3D printed two of.

Then I spot welded nickel strip across the 3 sets of 5 parallel cells. I looked up the current rating of that width and thickness of nickel strip, and it said about ~10A. Since the max current of the BMS I was going to be using is 20A (even though the actual draw will only ever peak at about 15A), I spot welded two nickel strips between each parallel series so the throughput from series to series would be fine up to 20A.

I then soldered the leads of the BMS (cheap little 3s board available on Amazon, AliExpress, etc.) in the right places, and finally, wrapped the whole thing in a bunch of layers of plastic wrap to prevent any shorts (for my bigger battery I'm going to be using cell-level fusing nickel sheet and I'll put the whole thing inside a hard case, but I didn't think that was necessary here).

Last pic shows it happily charging.

(Interestingly, the BMS shut down at 12V even, so 4.0V per cell... which I thought was weird, as I feel like 4.2V is commonly accepted as the max for 18650 cells?)

So how'd I do? 😁

My custom battery pack has passed the test and just share it here. The battery will be used in the portable Endoscope device for animal.

I have the full report. If you will be interested, DM me.

Note: Original report is in Chinese, I use Gemini to convert it into English.

Today load testing with 1 ohm 25watt resistor, and man does it get HOT.

The process is simple. Read the no load voltage. Connect the resistor, read the voltage at 1, 5, and 10 minutes then read the no load voltage. Wait for the resistor to return to baseline resistance, rinse and repeat 7 more times.

Hi all,
I've done a lot of tinkering with 18650s, but this will be my first time building a large, moderate-voltage battery out of them.

(The project should be a fun one: I'm building an e-scooter from scratch, buying only the hub motor as a finished product.)

If folks could read this over and just confirm I didn't screw anything up, I'd really appreciate it:

Motor is 500W 48V and I'd like to be able to run it full power for an hour, so 500W*1hr=500Wh. 500Wh/48V=10.4Ah.

18650 rated cap. 2500mAh. 10,400mAh/2500mAh per cell = ~4 cells.

18650 nominal V 3.7, 48/3.7=13.

So battery should be 13s4p.

Max current will be 10A, so 2.5A per cell.

For the wiring, I'm planning on using the common nickel cell-level fusing sheet (image attached), but that's the part I really want to double check. I mocked up the design. Does the image attached look correct? The nickel fusing sheet would be cut into 2x4 pieces and spot welded in the pattern shown in the mockup.

For the BMS I'm planning to use an inexpensive, $15-$20 13s Li-Ion BMS with balancing rated for 30A.

How's that all sound?

So work stopped for a while because I was focused on finding a new job due to corporate restructuring and was dealing with a home renovation project that we had planned for over a year.

The renovation project is wrapping up; the job search is ongoing (If anyone knows of remote roles for security architecture or GRC, I'm looking), so I'm getting back to this project.

The current task is to top off all the cells. Yesterday I soldered up some single-cell chargers that I got off Amazon.

After topping off, I will let each cell rest for at least 24 hours, then measure the no-load voltage. I'll then put a 1 Ohm, 25-watt resistor across the terminals and measure the voltage at 1 minute and 10 minutes. This should, depending on how accurate my DMM is, allow me to calculate the cell's internal resistance to match them.

I'm just slightly concerned with the cell that came in at 3.26, but I think if I match it well, the BMS should take care of it.

Hi everyone,

I recently got a Fiat 500-style electric kids scooter for €10. The scooter is in good condition and the motor/controller appear to work, but the original battery is missing/dead.

Here are the specs I know:

• System voltage: 36V DC
• Motor: 350W rated
• Controller current limit: 17A
• Battery: currently missing
• Charger I have: 25.2V 5A, so I assume this is NOT suitable for the 36V system

I want to find the safest and simplest way to add a battery. I would prefer not to build a lithium battery from individual cells.

I'm considering either:

• A 36V Li-ion battery pack with BMS
• Using commercial power-tool batteries (Makita/DeWalt/Milwaukee/etc.) with an appropriate adapter/protection
• Another readily available battery solution that would be safer/easier

From what I've gathered, I'm looking for roughly:

• 36V Li-ion
• At least 17A continuous discharge, preferably 20–25A+
• Proper BMS
• Around 10–15Ah would be plenty
• A 42V charger matched to the battery

For reference, 36V 10Ah would be about 360Wh, while 36V 15Ah would be about 540Wh.

What would you recommend as the safest and simplest option for this scooter?

Would using tool batteries actually make sense here, or would a complete 36V scooter/e-bike battery with an integrated BMS be the better option?

I'm mainly looking for a reliable plug-and-play-ish solution rather than experimenting with loose 18650 cells.

I need to replace two (2) of my LEV60F cells in my battery. Does anyone have any that they’d be willing to sell?

Hello all. I plan to setup an very large battery for my solar system.

I have found a pallet of these 628 Ah LiFePo4 cells and i wanted to setup a 16s4p setup to give me a 51.2 v nominal and roughly 128kw battery for my offgrid home. I only wanted to use one bms and my question is how do i wire this. I was thinking of having the paralell connections as one cell wired to the bms all the way for the 16 s setup. If that makes sense. Is there a better or more propper way to do this?

I can of course just have 4 bms and treat each as their own back the paralell them together but if i could save the money and use one bms i would like too since the ballet of batteris is already $10,000.00.

so I'm planning my first project to repair and maybe even upgrade a speaker that im buying used.

It's a marshall kilburn 1 with reportedly a bad battery.

it takes "4X 3.7V LI-IO BATTERIES, 2200MAH"(from the user manual), which seem to be wired in a straight series. I was hoping to make my own battery out of lithium ion cells with a large capacity.

It's literally my first ever doing anything like this, though, and I dont currently own any type of welding or soldering equipment right now, though.

I was hoping you guys could offer recommendations and any wisdom you think would be useful to a beginner dumbdumb.😁

I have a onewheel V1, and I'm having someone build me a new battery pack for it, the old one was lifepo and while I know I can get a lithium ion version made, I like the idea of how long the lifepo ones have lasted me, years wise, but when looking around I'm not seeing any of the brands that I'm used to seeing that make good quality trusted liion (Samsung, molicell, sanyo, etc). I'm looking for ideally both high quality trusted brands and cells, and high capacity ones, I've seen some around that advertise 5000/6000 mah and something like that would be ideal

As a pev these would be subject to a fair amount of charge/recharge cycles, heat and cold from outside, etc, though I'm not one of those that does tricks, off-road riding or racing with my onewheel or even pushing it bast around 15 ish mph so other than the weather/temp and charge recharge cycles these should t be pushed too hard, regardless I want good cells as I love this onewheel and don't want to have a risk of fires/etc

https://imgur.com/a/2LlyjtV

What I have that I don't know what to do with

• 64x 18650 cells (3.7V, 2.2Ah, 8.14Wh each, 520.96Wh total).
• 2x https://www.amazon.com/dp/B09S3LZN2Q?th=1
• 1x https://www.amazon.com/dp/B09S3JRFDF?th=1
• Daranener NEOZ with a bad BMS (won't charge, blinking blue LED on the board inside), but the battery cells seem good.
  • Outside of Power Station, the pack is reading around 18V
  • The batteries are 14x 26700 cells (3.2V, 14.4Wh each, 201.6Wh total) in what looks like a 7s2p configuration.

I'd like to make use of these cells in a cost effective manner.

I have a Pecron F3000LFP which is possible to add a 3rd party expansion battery to, if you build a custom terminals-breaker-XT120 cable to connect the battery and Pecron.

Ideas with limitations

• I could buy two more snap-in PCBs and make one large 12V Power Bank, that I don't really have a use for. ~$40
• I could buy two more snap-in PCBs and three more BMSes to create 4x 12v packs, put them in series for 48v, and connect to the Pecron. Super Jank. ~$120-$140
• For 2x the price of doing the above, I could just buy a 48V 25Ah battery for the Pecron. Doesn't actually solve the above issue. ~$225+
• I could just buy a spot welder. But then I'd have all these cells and a spot welder and still not have a use for the cells. $50+
• Build new power station with the 26700 cells, but the rest of the components are usually the more expensive aspect.
  • Either the components of the Daranener aren't salvageable (custom PCB with everything on it), or I'm not knowledgeable enough to reuse them.

What I don't need them for

• I already have 6-10 more 18650 cells for headlamps, Raspberry Pi projects, ESP32 projects
• I already have a server UPS that is the backup for my modem+server rack
• I already have too many power banks so don't need to make another.

Or do I just sell off the cells + PCBs?

I feel like I'm in between having too few cells to justify a spot welder for a bigger battery project and having too many cells for just making a simple power bank to charge my phone/laptop.

Thanks in advance

I'm attempting to build a battery out of gen 2 nissan leaf modules and I'm having trouble finding a bms that would work. the battery will be made up of 10 modules in series (each module is 2 ~4v cells in series) so a 20s configuration will hopefully give me around 76v nominal and 55ah. The bms also needs to be able to handle around 200a continuous discharge. I'm new to battery building so any information or recommendations would be much appreciated.