There are several CAN based BMS solutions on the market, this topic is not about which one to choose, it is about a design choice.
Say you have some battery modules paralleled, and they don't have their own BMS. They have their own slave CAN bus module which talks to a master one.
I see two ways in the market of how the contactor placement is solved.
1: Place a contactor on each module. In case of an issue, they open all contactors. And close them also at the same time.
This is done against huge balancing currents, to keep them at roughly same state of charge.
2: Permanently parallel the battery modules together, and just have one contactor for the whole pack.
I am assuming you put a fuse on each module, regardless of which method you have.
Which one is better?
I must add that the contactors typically don't have to work so much, they are typically just on and they don't have to intervene.
I have the second way already running for quite a long time at my house. But the batteries aren't pushed that hard.
I guess, if you would have a short in one cell, the other battery modules could dump it into that faulty battery module. A fuse could still intervene, but might not be triggered.
But on the other hand, that is the worst case scenario, and a BMS might not be able to solve anything at that time.
Say you have some battery modules paralleled, and they don't have their own BMS. They have their own slave CAN bus module which talks to a master one.
I see two ways in the market of how the contactor placement is solved.
1: Place a contactor on each module. In case of an issue, they open all contactors. And close them also at the same time.
This is done against huge balancing currents, to keep them at roughly same state of charge.
2: Permanently parallel the battery modules together, and just have one contactor for the whole pack.
I am assuming you put a fuse on each module, regardless of which method you have.
Which one is better?
I must add that the contactors typically don't have to work so much, they are typically just on and they don't have to intervene.
I have the second way already running for quite a long time at my house. But the batteries aren't pushed that hard.
I guess, if you would have a short in one cell, the other battery modules could dump it into that faulty battery module. A fuse could still intervene, but might not be triggered.
But on the other hand, that is the worst case scenario, and a BMS might not be able to solve anything at that time.
