I have my eyes on the JK active balance BMS and will be building 10S2P battery with P42A cells so the total battery is rated to 90A but my ESC (currently) only pulls 30A. I will be looking to upgrade in the future but for now that’s my setup. I want to future proof the battery pack for more powerful ESC’s and can either buy a BMS with 80A max discharge or go for the cheaper one and just bypass the discharge. Bypassing the discharge also leads to a much smaller BMS which is a big advantage. I have two questions:
- Is it dangerous to bypass the discharge completely? What short circuit failure can I build instead?
- Will bypassing the discharge lead to a problem with the active balancing of the cells? Are there any features of the smart BMS (other than max discharge protection) that won’t be available to me?
Thanks a lot for the help!
When you bypass a BMS it’s only bypassed as far as discharge is concerned, which means standard charging and balancing are not affected
But you are reliant on the ESC(s) to protect the battery from being over drawn or over fed (under voltage or over current on acceleration and over voltage or over regen current on deceleration)
I wouldn’t worry about short circuit protection because if you trigger the short then you have no brakes and that’s an easy way to get yourself killed since skates have no mechanical brakes
Thanks a lot! The VSC I’m using only pulls 30A max and the pack is rated for 90A (Molicel 42A in Series of 2) so I don’t think the VSC pulling more from the battery than possible is a consideration here. Would you agree? Is there any risk from the Regen with this route? As I said before, the smaller the better for the BMS but I don’t want to do anything stupid and want to make things safe.
As the ESC is pulling more from the battery than it can take, this isn’t really a risk as if I upgrade the ESC, it will be to a programmable VSC so again can manage things fine there.
Thank you for confirming that bypassing the discharge won’t affect the active balancing. It was almost impossible getting JK to confirm this. Their customer service has very little technical knowledge.
So the last question is that you don’t think any kind of short circuit protection is necessary?
Or would a short, most probably just blow the ESC anyway so there will be a break in the circuit?
I just want to make the setup as safe as possible.
That battery is more than enough, I wouldn’t worry. I’d skip on the short circuit protection on the ESC side, a fuse between the charger and BMS is very important to keep your house from burning down
Thank you for all the help! Really appreciate it.
Can you give me an example of a fuse I can use for the charger port? I’m really sorry but don’t know what to search for.
Look for a 58v rated mini blade fuse and an online holder, then pop it in the positive side