Dual BMS, in case one fails?

[guerney]

Do dual BMSs exist for ebike battery packs?

 

[saneagle]

Do dual BMSs exist for ebike battery packs?

You already have many of the functions doubled up by the charger and controller. The only thing not covered is balancing, which is why I'm so against people doing charging procedures that stop it from working. If you wanted to cover that, all you need is a smart BMS that you can control and monitor with a smart phone.

Covered by charger and BMS:
Minimum voltage alowed for charging
Max voltage cut-off

Covered by controller and BMS:
Minimum operation voltage
Maximum discharge current

You should also have a fuse for the max charge current, which can be in either the battery, charger or both.

When I've been testing batteries, I found many where one or more functions were not working, mainly low and high voltage cut-off, but nobody would have known because the charger and controller have them covered, and they're normally ahead of the BMS.