JK BMS incorrect voltage under discharge (with pictures)

[Block]

Hi all,

I have a JK BMS on a 14s pack leaf pack.

The cells all populate correctly on the app, but once the pack is under any load over 5 amps one cell will show crazy voltages, seemingly at random. Using a multimeter I have verified that all cells stay balanced while discharging. I am using a programmable load and slowly creeping up the discharge. The JK app starts displaying wrong voltages above 600w, and shuts off discharge.

Pack wiring and overall setup seems fine, and has been cycled recently. It had a smaller dalybms, but was upgraded for the higher recharge/discharge rate. I’ve rewired and rechecked the bms leads a few times, definitely roast it if you notice something that could be improved. Red leads are for the JK, yellow leads are unused for now.

Thanks for any advice

 

[sunshine_eggo]

dang leaf modules...

(2S5P)7S configuration.

The > 4.20V makes me cringe.

It looks like you have your balance leads connected to a terminal block. The more connections you have yields more chances for failure. There is either a connection issue somewhere between the cell terminal and the JK sensing pin, or the BMS is faulty.

 

[Block]

Hey, thanks for the reply.

I should reiterate that the BMS screenshots are NOT the actual cell voltages. No cells are even close to 4.4v, or 3.6v when checking with a multimeter.

Had the same idea to ditch the terminal block. The BMS cell taps (red wires) go directly to the Leaf cells. Cells populate fine, no resistance problems.

I don’t think it’s a weak cell problem either, as the extreme low cell jumps around, while other cells seem to increase in voltage at random...

Weird problem. Spitball if you have anything..

 

[squowse]

Hey, thanks for the reply.

I should reiterate that the BMS screenshots are NOT the actual cell voltages. No cells are even close to 4.4v, or 3.6v when checking with a multimeter.

Had the same idea to ditch the terminal block. The BMS cell taps (red wires) go directly to the Leaf cells. Cells populate fine, no resistance problems.

I don’t think it’s a weak cell problem either, as the extreme low cell jumps around, while other cells seem to increase in voltage at random...

Weird problem. Spitball if you have anything..

Ive had this with JK bms as well. At the time it was suggested that it was the balance lead connections

 

[9th]

Check the "Con. Wire Res. Settings" if it's all zero.

 

[Block]

Fixed this issue shortly after, but forgot to post the answer here. It was a programmable load causing problems.

Before spending days running in circles over one component, I should have checked the whole system for other devices causing interference. After switching to a different load (heater) the BMS and cells have shown no spikes for the past 2 months.

 

[squowse]

W

Fixed this issue shortly after, but forgot to post the answer here. It was a programmable load causing problems.

Before spending days running in circles over one component, I should have checked the whole system for other devices causing interference. After switching to a different load (heater) the BMS and cells have shown no spikes for the past 2 months.

Whats a programmable load and how did it affect the cell voltage readings?