I want to create a modular battery system

I want to create a modular battery system

The modules would be 16.8v, 4 cells in series and 10 parralel, around 300Wh each

Okay, for a 4S you would need 4 modules - this kit has all the parts you need for that

[DIYBMS V4.40 x8 Modules (KIT) - Shop | OpenEnergyMonitor]

you will also need a controller board [https://shop.openenergymonitor.com/diybms-controller-populated-pcb-kit/]

On top of the parts that come with the kit you also need a WEMOS D1 MINI PRO and some JST cables to connect everything together.

I already checked the link and I’m sure it wil work good, only I’m wondering if anyone would make a new PCB layout integrating 4 modules in one for space saving purpose

The modules are tiny and are designed to be isolated and standalone, so merging these onto a single board would also increase heat - you need the modules as close to the cells as possible - short cables as possible.

Because I’m limited to 10 cells parallel I can use lower currents for balancing, I’m trying to make something like this: (it’s not finished yet, first time working with eagle)

Hi @Lex_Poel, what are the drawbacks to using the existing design? Are you just building a PCB for fun?

@stuart I want them side mounted (on the small side) of my battery packs. Using 4 small prints and stacking them isn’t the prettiest solution in my mind

I want one small print here:

@Lex_Poel, they are neat. Were they preassembled?

@Lex_Poel looking at the battery you have built that is 6S20P - 6 in series (about 24v).

You will need 6 cell monitoring modules for that, not 4 - you don’t put them on each of the “rows”

Home made with scrap lithium batteries from work and 3d printed covers

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They are connected like this

Okay, wouldn’t it of been easier to just build a 4S pack instead of multiple 4S packs?

You are now going to need 12 monitoring boards instead of 4.

It would be easier indeed. Only it misses my point of creating a modular system. So now I’m trying to make one small PCB containing 4 of your modules. So one battery pack has one slightly larger (more expensive) module instead of 4 small modules

Given that the existing module is only 30mm wide, it would have been easier just to glue 4 of these onto a board and wire them to each other!

i’m going for a size of 5x7cm

The final first version of the 4S DiyBMS with half the discharge rate.
Current size 62x53mm

At the end of the month, I will order the first prototypes for testing :slight_smile:


Looks nice.

Did you improve or make changes to the circuit at the same time?