Does it matter what the voltage difference is in my series connections?

[Kadenmac]

Hello,
I am building a 20s 12p battery pack and I have made the parallel packs already and when making them they were all the same voltage. Does that also apply when making a series connection. If so what is a safe voltage difference? I am using a bms by the way if that matters.
Thanks in advance.

 

[spinningmagnets]

The closer they are in voltage, the easier time the BMS will have balancing the entire pack. In theory, a different voltage doesn't matter much in the series connection, because you can series two packs of completely different voltages.

A 12V pack added in series to a 36V pack will make a 48V pack.

 

[john61ct]

Yes, called manual balancing, ideally would have sorted the cells so that each parallel group were as close as possible in total capacity.

The goal if using a cheap BMS doing the balancing, is to try to minimise the work it has to do.

With quicker more capable balancing gear, not so critical even if a lit is required more frequently say once every 20 cycles, 10min is enough

 

[Kadenmac]

The closer they are in voltage, the easier time the BMS will have balancing the entire pack. In theory, a different voltage doesn't matter much in the series connection, because you can series two packs of completely different voltages.

A 12V pack added in series to a 36V pack will make a 48V pack.

Ok thank you for the help.

 

[Kadenmac]

Yes, called manual balancing, ideally would have sorted the cells so that each parallel group were as close as possible in total capacity.

The goal if using a cheap BMS doing the balancing, is to try to minimise the work it has to do.

With quicker more capable balancing gear, not so critical even if a lit is required more frequently say once every 20 cycles, 10min is enough

Thank you for the help