Pop and smoke from reversed voltage sensing connector?

[jameshowison]

I was replacing a cell in a server rack battery. The BMS is a Pace BMS.

All was going well (voltage across the battery showed ~52v) until I went to put the white connectors back onto the board. See attached pic. When I put the second one in there was a “pop” sound and I smelled some smoke

I checked the voltage on the balance/sensing wires and all seemed correct (around 3.29 volts between each consecutive pair, ~52 across first to last)

Now when I attached everything and turn the BMS on it shows 0 volts for everything.

Perhaps I was putting the white connectors on upside down? Is that possible? They connectors have temp sensing wires in the as well, I think (the black pairs on the left of each plug).

Reckon the BMS is fried, right?

 

[Daddy Tanuki]

don't think thats possible with those connectors is it? did you have the mainpower and ground unhooked? most of the chinesium bms's you have to unhook the negative and positive and then attach all leads then hook up the negative and lastly the positive. at least thats how my chinesium BMS is.

 

[robbob2112]

Those connectors sure look like they are keyed so they are impossible to put backwards without major force and distortion.

 

[D71]

Those connectors sure look like they are keyed so they are impossible to put backwards without major force and distortion.

That last part is most likely the result.

 

[jameshowison]

No luck with trying with B- and B+ disconnected, then adding sensors, then reconnecting battery. Same result, exactly as if sensors were completely disconnected.

Figuring the BMS was shot anyway I disconnected all and flipped connector 1 upside down. It does slip on, without significant forcing, producing a small spark. This is without the BMS being powered up (B- connected but the small B+ wire disconnected.

That said, there are little ridges on the top of the male connector, matched by slots on the female connector. So y’all are right, it is keyed but even a very little wiggle defeats that and it slips right on. Gah.



Looks like flipping the connector would apply voltage to the pins supposed to connect to the Temp sensor cables. For connector 1 that would be ~13v and for connector 2 that would be ~23v and ~26v respectively. Guess that’s enough to fry something in the board. Rest of the BMS seems to work ok (ie turns in and can navigate menus).

 

[jameshowison]

I swapped the BMS out for another one and all is well. So, um, yeah, don't force the connector in upside down

 

[Daddy Tanuki]

I swapped the BMS out for another one and all is well. So, um, yeah, don't force the connector in upside down

Feel for you and as beer involved? I find the universal lubricant causes me issue’s sometimes