How close should the cell voltage be when assembling a battery?

Happy new year everybody,

I’m building a 10S5P battery and my cell voltage varies from 3.55V to 3.64V, two thirds of them are 3.55-3.56V, the other third is between 3.60V and 3.64V. Should I try to bring down the voltage on the highest voltage cells before I build the battery? I read somewhere that it’s important that the voltage be as close as possible…



its not that big of a deal. your lowest vs higher is 3.55 to 3.64 and theyll equal out as soon as you weld them all together. one will charge and one will discharge. youll be finee!


Super, that will save me some time, thanks!

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The parallel packs of 5 will charge/discharge themselves as soon as they are connected together. The voltages are not that off so you won’t damage anything.

When you put these packs in series, the voltages won’t balance each other out. A BMS can easily balance the cells for you after you build the pack. You can also individually charge each parallel pack before you put them in series to make sure your cells are balanced from day one.

Thanks for the info. I will be using a BMS so it should be fine :slight_smile:

you could hack a phone charger to charge the low cells and bring some of them up. I would. @barajabali you say the parallel cells will balance each other and the spread in voltage is not a problem but are you sure? It seems like a lot of power will be instantly flowing to balance. Maybe it’s rough on the cells with a spread of a tenth of a volt. If balancing cells by throwing them all in parallel I’m wondering how great a spread in voltage would be too much and damaging. Could be discharging and charging at a really high rate.

@pyttroll you could find matching cells and parallel them. Then you only have to charge a few cells before welding. Then series and balance the whole pack.