videosystm said:
I will look for a 150a bms and use that for my project. Thank you for all the help.
Something to note about BMS capability: they don't usually state *why* they are rated at a particular current, but if the reason is that the FETs may overheat at currents higher than that, then if your max current is over the rating long enough to heat the FETs enough to damage them, they could fail in a way that still lets current thru them but that the BMS cannot turn off anymore. When that happens, the BMS can no longer protect the cells because it can't prevent overdischarge by turning the output off.
It's a "silent" failure, in that there is no alert or indication this has happened.
The only ways to know are when a cell does go low enough to trigger LVC, and there is either a display (Bluetooth, etc) or LEDs on the BMS the user can see that indicate this, or the cell goes so low it has a problem and fails in a catastrophic way or at least one that prevents the system from operating correctly so that the user will notice, and then test the pack / BMS. Or if the user does during-ride cell-level monitoring, or is testing often enough to see the problem.
Also note that not all BMSs actually shut off on overcurrent, some just have a rating for max allowable current, so before depending on this function, make sure the one you choose supports it.
Most systems use the controller's battery current limit to ensure the pack is not stressed.
On a Kelly controller, it isn't always straightforward how to set that; some use a percentage of the phase current limit, and the phase current limit is a percentage of the max allowable current, making it even more complicated.