it's can be very dangerous !!!!!!

cristof

cristof

Member
Joined
Sep 30, 2017
Messages
117
Hi everyone,
I was buiding my first 14S/18P mono-block batery, after a few hours, it was time to install and solder the BMS.
The BMS multi wire connector was disconected from the board, I was ready to solder the 5 last wire.....
for sure I did something wrong !
a short circuit with a wire, and one cell becam as a "rocket"
I just had time to cover the batery with a tea towel and send it outside home !

BE CAREFULL !

Cristof = 1 / AVERAGE JOE = 0

Cristof =1 - AVERAGE JOE =0


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How did that cause the cell to get that hot that it exploded? I see you're bypassing the fuse with the purple wire but the fuse on the exploded cell didn't disconnect it?

That's almost looking more like a bad cell than a something caused by a short circuit? Are you testing capacity and self-discharge ahead of time?
 
Accidents can always happen. Pack seems solid, well fused and that bms wire is not that thick to have caused such a short. My opinion is a faulty cell. After seeing this I will be more carefull while building packs and soldering.
Thanks for sharing.
 
That's a huge pack. I imagine you don't recall if that one cell was behaving oddly prior to adding to the pack. By oddly I mean was it hot during charging, was it below 1v when you first tested it, did it have a high IR?

Glad no one was hurt but damn that looks like it was scary.
 
Maybe the cell was charged to a higer voltage than the rest ? and get hot while balancing with the other cells...

It is a good thing the faulty cell did not ignite the other cells...
Isee one that seems to bea bit bulging also... do i see this right?
Keep the pack on a safe place (outside) for a few days, just to be sure...


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Interesting. Wonder what happened. Yes its sad at same time of course.
Important to try to find out what really happened so we all can learn from it!
 
I don't know what has happen exactly, but I first heard the caractaristic "short circuit" sound (in french... "PAFF"), and after the explosion.
I will clean all tonight and had a look if it can be repair.
All cells have been tested with OPUS 3 weeks ago, and were close to 4,15V before I put them together.
May be the wire went between the CID and Minus side, I don't know.
All the fuse were solder 24 hours before, and when I started today to solder the BMS wire, none of them was 'hot"
the bms wire was disconnected from board.
 
Do you have fuses on both sides? If not my only guess is that you shorted the fuse-based side.
 
It's possible the cell had some internal pressure which pushed up the metal positive cap and shorted through the insulator which melted when soldering. You can see the insulation in a video I made here, it's a pretty small plastic washer protecting the pairing from negative:
 
As with any DIY project the potential of something going wrong is always very high. Everyone doing their own thing to accomplish a goal. There generally are no quality control checks, at any stage in the DIY build, therefore the chance for error is always very high. Honestly, I'm surprised this doesn't happen more than it does. I personally have checked and rechecked my individual packs multiple times and still do not trust them. I'm constantly worried that I may have done something that could cause a problem like this or worse. We should all caution on the side of error and check and recheck multiple times before going live or making modifications.
 
Were all the batteries precharged or have around the same level as the rest of the pack? Otherwise it could have been charging at high amps from the other cells while still under the fuse rating. Then combine that with some dubious cell that just didn't like the high rate of charge caused it to erode.

Also, did you use tinned copper wire? When I first looked around I found a lot of resistance wire that were in the same gauge. Looks almost the same but it would fuse at a much much much much higher current.
 
Personally I would say it was a short to the cell directly that caused that. I've had only one cell do that to me when I shorted a cell but that was a sayno heater to begin with. With your BMS they should be attached to the buss side not the Cell. Just a suggestion
 
Yes DAROMER I Have fuses both sides.

I have started to repair, and was surprise to found inside the cell holder, only the dilectric.
I found the 18650 casing (Box? tube ?) on the floor
in fact the cell has shoot my workshop ceiling !
for sure, it's must be a SAMSUNG cell from North KOREA !


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That's quite a projectile. What was the cell brand? Looks like a generic, could be a "refurbished" cell from China without any safety features (CID) to save cost.
 
hi Cristof,
This is crazy how the casing made that hole in your ceiling!!! I would have never imagine the power to pop out like that O_O
 
cristof said:
Yes DAROMER I Have fuses both sides.

I have started to repair, and was surprise to found inside the cell holder, only the dilectric.
I found the 18650 casing (Box? tube ?) on the floor
in fact the cell has shoot my workshop ceiling !
for sure, it's must be a SAMSUNG cell from North KOREA !


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Click to expand...

Was that cell upside down (wrong way) in the pack? Normally these cells will eject (vent) out of the top versus the bottom. The other cells in the same row appear to be negative side up. This one seems to be positive side up if the ejection theory is correct.
 
Hi All,
the cell was : LGES318650, comming from an old laptop batery pack.
when it has arrive, the 48V batery block was "flat" on the table.
the positif side of this cell was looking the table.
On the table, I had a tea towel to protect connnexions.
I have a video 30 second befor it's happend


My Youtube chanel : https://www.youtube.com/user/Cristofguerin/videos

mike said:
Did it actually cause a fire or is that black on the battery just from residue/dielectric?
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it's just residue from the "Rocket", no fire at home.... :mad:
 
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