Do I have a wacked out BMS?

[Rednecktek]

So I picked up some 52Ah cells and made a 24v ammo can build for giggles (honestly, it's not an addiction, I can quit any time I want) but there are a few things it's doing that make me wonder if my JBD BMS is bad or just weird.

1: When I disconnect the balance leads, I still have full voltage to the terminals. On my 4s builds when I disconnect the leads and put a meter on it there are 0v so seeing 27v strikes me as odd.

2: I've got both a runner AND a lagger so I ordered a 5a active balancer and I was wondering if I need to tear half the bolts out of my pack or can I just unplug the balance leads from the JBD and plug it into the jack on the balancer. As I understand them it doesn't NEED the BMS or charging to do its job, just time. Can I just move the plug and give it a couple days to balance everything out?

3: The Overkill app works with all 3 of my 4s 12v batteries but has refused since day 1 to talk to the new 8s. I've had to resort to using the Xaioxiang app and be quick on the selection to see the info. Has that happened to anyone else?



So is my JBD wonked and needing replacement or am I reading something into nothing?

Thanks y'all!

Yes, I know they're Grade-B but it was a toy box so I wasn't too worried about EV grade-A perfect pristine cells. Some tight pulls with the packing tape solved the bulging issues.

 

[Quattrohead]

Doesn't sound right to me.

 

[DIYrich]

1: it could be that on one bms if it sees 0v, it thinks under voltage and shuts off battery, or it gets power from one of the leeds you disconnected.

2: verify the leeds can handle 5amps.

 

[Rednecktek]

1: it could be that on one bms if it sees 0v, it thinks under voltage and shuts off battery, or it gets power from one of the leeds you disconnected.

It's reading 28.4v on the C- and Pos+ terminals whether or not the BMS leads are connected. It just strikes me as odd that doing the same thing with the other two 4s BMS's I get 0v between C- and Pos+ with the balance leads disconnected and 13.8v with them plugged into the BMS.

2: verify the leeds can handle 5amps.

Good point, I'll have to look that up. The balance leads are 20AWG according to my strippers.

EDIT: Good thing I asked! Looks like 1.2a-1.5a is all those leads can handle, not gonna be able to throw a 5a balancer on there. Time to break out the deep socket.