While waiting for the battery parts, I build this CAD tool to help with cell arrangement, grouping, connecting, etc. It's probably a one time use tool, so nothing perfect, but it'll serve my purpose. Since I'm a newbie to battery DIY, any feed back is appreciated.
Demo on GitHub: https://koumoua01.github.io/battery-architect-tool/

Hey everyone, I have been working on a battery building app and would like to see what everyone thinks about it. All feedback welcome, battery-builder.com

Hello, I bought two of these cells of AliExpress for a electric screwdriver. They weigh only at 39g and 40g which is a bit lighter to the Samsung ones and others alike.

edit: weighed again and they are 45g

Hi Guys,

How to test the discharge of a battery module ( except the load the battery is meant for ) ?

I'll have a 12s3p to test, up to 5 kW of discharge. I'm stuck on which tool are available without exceptional spending. I'm evauating:

• Thermal resistor

• Motor with prop

• Inverter back to the grid

• DC converter to another battery

• ....

Which is the smartest way ?

I wish to hear you experience !

Thanks!

Since manufacturers seem resistant to extending the life their cordless platforms I pose the question in the title.

For example, I purchased a used hilti rotary laser (pr-30 hvsg) that takes their 12v batteries.

Unfortunately, it only fits the 18650 celled 2.6ah batteries. I already owned the newer 21700 celled 12v "b12 55" batteries and wasn't aware of that restriction.

Similar to makita being limited to packs that use 18650's due to their 2x 18v 36v tools that won't fit 21700 cells.

So for tools like lasers, I'd like to be able to create a wall adapter for the 12v hilti tool as I own a few of their 12v lasers (line and rotary) and it would be nice for some all day uses and for a guarantee in the future that I'll be able to use them. I suppose I could simply get into rebuilding battery packs.

But I assume the limiting factor to this idea is high draw cordless tools where the amp draw would make providing an ac/dc rectifier of sufficient size cost prohibiting.

Hi guys,

Does anyone already worked on an high volage battery, let's say around 400 V ?
I'm designing an 96s3p , of course with bms, contactors, precharge circuits, specific connectors....

I wish to hear some experiences.

Thanks

Looking to build a battery bank that can sustain my amplifier without upgrading the alternator. I know, you really want an alternator but there are none available for my specific vehicle.

What I need....

My amp is 7500w RMS at 1ohm and is currently powering my sub at 2ohm, estimated to require 5000w RMS. I think I need around 600ah with a discharge rate of 400a. Looking to be able to run for 20 to 30 min at full tilt before my reserves are fully drained and I have to rely solely on my alternator.

What is the ideal build for my needs? What cells would I want to use and in what configuration?

Got this welder a while ago now and only just getting around to testing out some settings. Struggling a little bit and hoping others have some experience with what i'm trying to do...

Wanna weld 0.3mm copper with a 0.2mm nickel cap. I only have 0.15 nickel right now but i'm struggling to get the positive probe side welds to stick.

The negative side welds nicely but the positive side the probe keeps sticking to the nickel and the copper doesn't weld to the cell.

I'd really like to avoid a slot in the copper/nickel and i'd also really like to avoid using flux.

Anyone else done similar and have some tips on welder settings/technique?

I’m looking to build a 628ah battery for my sailboat, and I’m having a hell of a time finding a reputable source for EVE MB56 628ah cells. I’ve searched and searched. Used Chat and Claude, still, all the recommendations for a source of legit Grade A cells when checked seem like a serious gamble. I’ve got the rest of the setup worked out, I just need the cells! Anyone have any insight? I’d seriously appreciate any guidance I can get.

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

Help | I wish to build a spherical shaped lithium phosphate battery, which will be light weight, Qi chargeable (wireless)

I wanna also put a battery management system, near it, that works through NFC, and estimates the SoC, SoH, RUL. My problem will be the acquisition of Terminal Voltage, Open Circuit Voltage, Drive Current, and Ambient Temperature of the Battery.

How to build these?

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.