Spark from a wire in battery, unclear cause

[Pacto]

I was putting a 48V Himiway Escape Pro battery back inside its case when a spark suddenly flew from the red wire. The burn marks can be seen in the photos. What's strange is that the wire did not appear to be in contact with anything else, and there's still continuity in both of the two fuses of the battery. The charging and output voltage also appear to be normal afterwards. Any idea on what could have caused the spark? And is it likely to present a hazard from then on?

 

[amberwolf]

Given the plasma burn on the edge of the case, I'd guess the battery negative is grounded to the case inside, or if the case is mounted to something else then that something else is grounded to battery negative. Then the edge of the case was touched by that exposed metal of the holder for the white tube (fuse?) that's on that red wire, allowing a short across the pack.

The fuses are intact at least partly because they are both apparently (or possibly) *past* the point at which the short occured, so were not in the current path.

Until the electrical connection to the case is removed, it remains a hazard.

Same for the uninsulated holder terminals.

 

[Pacto]

Given the plasma burn on the edge of the case, I'd guess the battery negative is grounded to the case inside, or if the case is mounted to something else then that something else is grounded to battery negative. Then the edge of the case was touched by that exposed metal of the holder for the white tube (fuse?) that's on that red wire, allowing a short across the pack.

The fuses are intact at least partly because they are both apparently (or possibly) *past* the point at which the short occured, so were not in the current path.

Until the electrical connection to the case is removed, it remains a hazard.

Same for the uninsulated holder terminals.

That fuse holder is normally covered by a plastic case. It's the white thing on the right in this picture. Definitely a huge mistake that I didn't put on the cover before doing anything else.


The batteries are separated from the case by shrink wrapping. Would it be sufficient to add additional insulating tape to the two ends where the wires come out of?


What sort of damage to the battery is likely to have already happened?

 

[amberwolf]

Probably no damage so far, unless the BMS was involved in the fault. Does the BMS correclty turn off the input when charging and any cell reaches full? Does it correctly turn off the output when discharging and any limit is reached (LVC, overcurrent, etc)? If so, then the BMS is ok, too.

But, you still have *something* that allowed battery negative or some point in the pack more negative than that fuse terminal to contact the casing. I don't know what it is, but there had to be a current path, and that path goes thru the casing, so....

It's probably actually good that this relatively innocuous event happened, so that you now know there is such a fault in the insulation somewhere, and you can then find it and fix it before something really bad happens (like a short between cells at opposite ends of the pack thru the heatshrink allowing them to touch the casing, etc).

 

[Pacto]

Yeah this could have very easily been a disaster. It looks like the negative side of the battery is indeed on the left (from the perspective of the first two photos), so it could have contacted the uppermost part of that red wire's metal fuse holder somehow. How exactly that happened through the nonmetallic wrap and casing is still baffling.

The charger normally displays red when charging, and turns green when the battery is fully charged. This still happens, so is it safe to assume the BMS is still working at least with regards to charge management? I'm not sure how to test the output stoppage though.

 

[999zip999]

I made a 12s pack of A123 20ah pouches and made neg and positive different lengths and could not touch I put it down on a hardware store vinyl floor. The leads 6in apart and a plasma ball jumped up. It spark thru the floor tiles ? No it was indoors and dry. I don't know how that happened I wasn't running to be a mess as being 20 ah. And no damage I could tell. Continuity from a vinyl floor ?.
There's a gap in a spark plug and it's able to jump.
A TIG welder you never touch the tip to the metal.
Thor can throw a lightning bolt.