what happens if B- is disconnedcted while balance wires are connected ?

[SammyMc]

Hi

I have a battery with internal BMS which seems good but has no BT function.
I intend to add another BMS externally (JBD smart) in series with the B- of the battery. The balance wires will be soldered to the original cables. So both BMS will see same cell voltages.

I have 2 concerns :

• does the 2 BMS interfere in voltage sensing (same balance leads).
• I read in BMS manuals that B- should be connected before Balance cables. So what will happen if the internal BMS disconnects ? BMS 2 (the external) will have balance leads (BC0 to BC16) without B- connection, will this blow the BMS ?

cheers

 

[DThames]

I can't say for sure but using a JBD BMS on a new battery build, I pulled in the balance cable first and then accessed via bluetooth. I had some nutty and incorrect readings....sort of freaked out and unplugged it. I finished the other connections (power connections) and connected it all back up. No problem, no damage. Maybe I got lucky, not sure.

Not sure what your goals are but if you just want to check cell levels, would a plug in monitor work for you?

 

[SammyMc]

Nice idea . will this battery monitor have BT or any wireless option ?

 

[DThames]

Nice idea . will this battery monitor have BT or any wireless option ?

No wireless or BT option. It does have some balance functions and low voltage cell level alarm.