Is it possible to connect two lithium-ion batteries in parallel with independent BMS?

I'm thinking about doubling the capacity of two lithium batteries in parallel with independent BMS. The two lithium batteries are new and the same model.

Yes, in the short term, this is fine as long as you load both lithium-ion batteries in parallel on the same startup SoC (the best practice is 100%) and try to make them around 0.1V.

But after a while, there may be a relatively large difference in the SoC of the parallel lithium-ion batteries, where one battery will turn on first and the other battery will have to carry the load alone, which is not very feasible.

There are many solutions to this problem, though:

  1. Are there any communication ports for the separate BMS to communicate with each other? If there is, then the solution is obvious.
  2. If not, try adding some actuators (DC contactors) at the output, which will turn on whenever one of the BMS is turned on (or logically with normally closed type contactors). Therefore, if one of the BMS is on, the whole system is off.

MORE: Does the 6S lithium-ion battery require a BMS?

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