Battery pack management system?

Hi everyone! I've been wanting to use multiple battery packs in parallel for a long time. As you may be thinking "That couldn't work cause the higher voltage pack will try to drain into the lower." and you're right. Wouldn't it be possible via power diodes?
I don't know what kind of diodes I would need, but I'm determined to get this right. Have any of you out there ran multiple packs in parallel?

TOPdawg said:

Have any of you out there ran multiple packs in parallel?

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Never been thought of before.
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Once you connect all the packs together including the balance connectors, they equalize. Once they equalize it just becomes one big battery pack. No power diodes needed. You can use one BMS to manage all the packs.

My 220ah 4s lifepo4 battery is actually 4x 55ah 4s packs connected in parallel. I been using it like that for 2 years.

As long as all the packs have the same voltage when you connect them together, there shouldn't be any draining between packs. They will charge up and discharge equally.

The challenge as I see it, is a current-limiting connection when adding a very low SoC sub-pack to a very high SoC "mother pack".

Or vice versa.

Letting them safely "equalize" without a charger involved.

Or even when the "mother pack" is being charged, in fact if the charger current output is much higher than what you'd usually use for the sub-pack on its own

I would think there would be very little "intra-pack" current flow exchange with the mother pack.

But ideally, the sub-packs could be connected without worrying about this, nor any voltage levels.

I think that initial "reuniting" connection would be fine via the power lead pair only.

The per-cell-level group connection between sub-packs only needs to be there while re-balancing maintenance is active, independent of whatever device does the balancing.