JK bms melted balance leads

[Alex1]

Are you going to get conclusive results on how this happened?

I dont know, but I think i will never find out what rly happened.

2P 8S eve 280 cells
I install new bms with pico 3A fuse with 1mm2 balance wires.
Is there point of compresing cells at this point?
In future I plan to switch to the 16S configuration to use it with deye inverter.
Im not satisfied with 35mm2 serial connection between upper 2p4s and lover 2p4s batteries, is there any batter way?

 

[Zwy]

Any reason why 2P 8S?

I don't really care for parallel cells in a pack. You get double the discharge amperage capacity (100A vs 200A) just adding another BMS and if one BMS fails, you have the ability to run off the other. Bank capacity is still the same with parallel single cell packs each with a BMS as 2P.

Balancing could take more amps than with single cells, there are 2 cells to take in balancing current. A BMS with 2A balancing on 2P is equal to 1A on single cells.

I noticed this spot



Where exactly did the balance leads run? If any balance leads were across the bare busbars, then it could have been the cause.

 

[Kornbread]

Did you use the m3 mounting holes on the back of the bms? That burnt area of the pcb is very near one of the 4 threaded m3 bolt holes. IIRC, the bolts that go in there can be no longer than 3mm. Is it possible a longer m3 bolt was used to mount the bms which shorted the internals, or eventually caused a short?

 

[Zwy]

Did you use the m3 mounting holes on the back of the bms? That burnt area of the pcb is very near one of the 4 threaded m3 bolt holes. IIRC, the bolts that go in there can be no longer than 3mm. Is it possible a longer m3 bolt was used to mount the bms which shorted the internals, or eventually caused a short?

You had me wondering so I checked. I had used 3mm x 6mm screws with a washer.

Plate is 1.85mm painted on both sides and the screw does compress the paint. Washer is 0.5mm thick.

This is what the back panel looks like on the inside.

 

[Kornbread]

Is there anything vital a long bolt could hit?

 

[Zwy]

Is there anything vital a long bolt could hit?

The circuit board fills the whole back from side to side and end to end. If the screw was long enough it could hit the board. I think about 7 or 8 mm might be the depth of the hole. I know if I put a nut on the 6mm long screw, it didn't have enough threads to hold.

 

[Kornbread]

Worried. I have to run out to the shed and measure the m3 bolts I got.

 

[Kornbread]

Looks like I have two different length m3 bolts, 8mm and 6mm. Used on small lock washer .65mm, and a flat washer 1mm, under the 8mm bolts and the bracket they are mounting to is 2.72mm. With the 8mm bolts that leaves ~3.63mm threaded into the bms.
@Zwy does it look like that will miss the board?

 

[Zwy]

Looks like I have two different length m3 bolts, 8mm and 6mm. Used on small lock washer .65mm, and a flat washer 1mm, under the 8mm bolts and the bracket they are mounting to is 2.72mm. With the 8mm bolts that leaves ~3.63mm threaded into the bms.
@Zwy does it look like that will miss the board?

It should be fine, mine is running in about 4mm.

 

[Frugal Devonian]

I've just had a mouse chew through two of my balance wires, happened as I was watching the app, I knew it was a mistake to wrap my batteries up in underlay for winter, I created a perfect nest site.