Is this setup possible?

[E-HP]

Absolutely. Best practice is to separate them for recharging (to the same voltage), but run them in parallel every time. That way, each pack only has to work half as hard, and they both get the same duty cycles.

If you don’t charge to full, the you can also keep the paralleled and bulk charge via the discharge connector. I do this 99% of the time.

 

[amberwolf]

If you don’t charge to full, the you can also keep the paralleled and bulk charge via the discharge connector.

If the packs are common-port BMS (no separate C- and P- pads on the board) then that is safe enough, as is charging via paralleled charge connections (as they are the same as the discharge), as there is full charge and discharge protection either way.


But if they are separate port BMS, then there is no cell-level protection in place when charging via the discharge connector, *or* by charging via the charge connector while leaving discharge connectors paralleled. That means if either pack ever has a problem with a cell group (they all will eventually, as they age), the BMS cannot stop charging it regardless of what happens.

 

[E-HP]

If the packs are common-port BMS (no separate C- and P- pads on the board) then that is safe enough, as is charging via paralleled charge connections (as they are the same as the discharge), as there is full charge and discharge protection either way.


But if they are separate port BMS, then there is no cell-level protection in place when charging via the discharge connector, *or* by charging via the charge connector while leaving discharge connectors paralleled. That means if either pack ever has a problem with a cell group (they all will eventually, as they age), the BMS cannot stop charging it regardless of what happens.

Thanks. I should have added if each pack had matched cells that can normally be charged to 80%-90% without going out of balance, then charging while paralleled should work. If made of unknown generic cells, then I wouldn't advise.

 

[amberwolf]

If made of unknown generic cells, then I wouldn't advise.

Unfortunately I would guess that the majority of packs fall into that category.

 

[99t4]

Moral of the story: If you want the most simple, convenient method for charging paralelled batteries, use healthy batteries that have common-port BMSs. They can be left connected together during charging, dischaging, and when at rest.