Multiple battery packs

[FFMan]

I'm just planning the addition of a 12kwh pack to augment my current 9kwh pack.

the obvious approach is just to join the 360v outputs and run them in parallel, which i think is fine but i was wondering is it safe to leave them joined in this manner long term. If i have contractors to separate them, there is a high likelihood they will drop back at slightly different rates and that there will be a voltage difference when i come to join them again.

They need to be joined for charging and driving so it most useful to treat them as one pack but i wondered what others have done ?

[tom91]

For a project I have them Parallel them at module level.

However I have a feeling your are missing a big big detail.

BMW PHEV, 9kWh gen 2 pack is 5 modules, 80 cells in series.
BMW PHEV, 9kWh gen 2 pack is 6 modules, 96 cells in series.

Connecting these together is a big bang.

[FFMan]

For a project I have them Parallel them at module level.

However I have a feeling your are missing a big big detail.

BMW PHEV, 9kWh gen 2 pack is 5 modules, 80 cells in series.
BMW PHEV, 9kWh gen 2 pack is 6 modules, 96 cells in series.

Connecting these together is a big bang.

just checking before i set off on along trip to get the second pack tomorrow.

My current 9kwh pack is 6 modules, 360v
The new 12kwh pack is also 360v in 6 modules just larger capacity cells is it not ?

i.e. current pack and proposed pack are 360v.

[tom91]

Oh okay then it is a Gen1 pack. If both are 6 modules then the voltages will line up.