When you had a cell go bad. What was the main mistake you did?

[Cyclomania]

I wonder what mistakes are to be avoided that other people have already made when making their lithium battery packs?

What happened to you when you had an accident or a cell that went burning or something like that? And how do you avoid that mistake when building your battery packs nowadays?

I want to know since I am a battery building noob that is researching the subject to avoid all mistakes and minimize thing that can go wrong. Thanks

 

[rafalg]

I had a battery fire at home because I thought it's safe to build it at my desk. One short circuit and battery started burning. Next mistake was a mosquito net in my window, couldn't throw the burning stuff out and had to take it to another room without the net. Another mistake was not having any fire extinguisher or a plan what to do when things go wrong. And finally, soldering nickel strips to cells is a bad idea. Nickel strips should be spot welded and for soldering use copper wires.

 

[Batteryrepair]

If you plan to use the battery at lower power levels that don't require cooling: double wrap the cells if you're going to glue them together. Use fish paper for insulation at spots where the nickelstrip could rub through and short, and use it a lot. Make sure balance wires can't move. Use Bimetallic charge temperature interuptors.

 

[Cyclomania]

I had a battery fire at home because I thought it's safe to build it at my desk. One short circuit and battery started burning. Next mistake was a mosquito net in my window, couldn't throw the burning stuff out and had to take it to another room without the net. Another mistake was not having any fire extinguisher or a plan what to do when things go wrong. And finally, soldering nickel strips to cells is a bad idea. Nickel strips should be spot welded and for soldering use copper wires.

What voltage of battery did you build and how much did it burn approximately? Did all the cells catch on fire? And was the fire concentrated to the battery or did it burst out onto the walls and floors and so on? Or was it more manageable? Enough so that you could pick up the pack in or with something and get it out of there finally? How did you get the fire to go out finally and how much damage did it do?

 

[rafalg]

No, luckily nothing caught fire except of the battery, there only was smoke and some soot. It was 10s6p battery, was almost finished when it shorted during soldering. Molten tin flowed between cell poles and shorted them for good, and almost immediately the thing started burning, first one cell and soon 2-3next. I was caught by surprise, after some messing around I threw the battery out to the lawn where it continued to burn. About 1/3 of it was destroyed, around half of the cells I think were still usable. And I had two more batteries on fire,one shorted when soldering too and another that I punctured when drilling some hole in the plastic holder. But these were smaller and I did the work outside. So, to sum up, 18650 cells seem to be very safe to work with, but if you connect many of them together then it becomes a bit more tricky. And it was stupid to do the work at home, with lots of stuff around that could just catch fire.

 

[Cyclomania]

No, luckily nothing caught fire except of the battery, there only was smoke and some soot. It was 10s6p battery, was almost finished when it shorted during soldering.

Hmm I think Inanek in one thread talked about soldering the series away from the battery, before he connected the strips to that battery. That way he did not have any soldering taking place close to the actual battery. I guess that could have eliminated the problem perhaps?

Because it was the solder that went from the positive side of a cell down to its negative side that shorted it or something like that right?

 

[Cyclomania]

No, luckily nothing caught fire except of the battery, there only was smoke and some soot. It was 10s6p battery, was almost finished when it shorted during soldering. Molten tin flowed between cell poles and shorted them for good, and almost immediately the thing started burning, first one cell and soon 2-3next. I was caught by surprise, after some messing around I threw the battery out to the lawn where it continued to burn. About 1/3 of it was destroyed, around half of the cells I think were still usable. And I had two more batteries on fire,one shorted when soldering too and another that I punctured when drilling some hole in the plastic holder. But these were smaller and I did the work outside. So, to sum up, 18650 cells seem to be very safe to work with, but if you connect many of them together then it becomes a bit more tricky. And it was stupid to do the work at home, with lots of stuff around that could just catch fire.

How did you manage to salvage the rest of the cells that were not affected?

I think I would have had a pretty high pulse at that point, so being able to save the rest of the cells sounds impressive

 

[rafalg]

just waited until the fire went out and stuff cooled itself. The battery landed in a moist, cool soil so it probably prevented it from burning itself completely. In all cases some cells were destroyed completely, neighboring ones not exploded but not looking good either, and the further ones almost unharmed. Plastic holders, wires - all junk. BMS board survived, i think.

 

[rafalg]

Because it was the solder that went from the positive side of a cell down to its negative side that shorted it or something like that right?

I was trying to solder a nickel strip to positive terminal of the cell, there was too much solder already and it didnt all stick to the strip. Instead, it flowed to the side, where the negative terminal is. And connected positive with negative. The cells were already connected in parallel so i think this is why the fire started so fast - whole section was shorted at once.

 

[batteryGOLD]

First point is tha structure. allways use cell holders or insulation card between S elements. and build a solid structure that could absorb electric veicule vibrations &impacts during ride. Battery will be shaked doin downhill on a ebike! and If U have a great fall, battery will spin kind of washing machine or slot machine

second thing is tha BMS, allways make sure bms have working high and low cut cells protection!
some bms´s sellin online from CN example d*aly and some other brands were reported to have faulty low cut limit and/or high limit cut at some units circulating worlwide..
when U build a battery, allways make sure to test battery to see if BMS low cut limit/high cut limit is workin. Otherwise U could have a faulty BMS at Ur battery, maybe 10%-20% probability, is this good or bad?

 

[Cyclomania]

just waited until the fire went out and stuff cooled itself.

Ah ok. How long did it burn for? Trying to figure out how long my battery would burn for, if it goes bad and I have it in the barbecue where I am going to keep the actually build within.

 

[Cyclomania]

First point is tha structure. allways use cell holders or insulation card between S elements. and build a solid structure that could absorb electric veicule vibrations &impacts during ride. Battery will be shaked doin downhill on a ebike! and If U have a great fall, battery will spin kind of washing machine or slot machine

Hmm what type of insulation cards are you using between cells? I have only seen cell holders. Not sure what insulation cards look like for batteries.

 

[batteryGOLD]

Hmm what type of insulation cards are you using between cells? I have only seen cell holders. Not sure what insulation cards look like for batteries.

only need to use insulation cards if no use of plastic holders. this way adds electrical separator between S elements, than U could use hot glue to give extra structure, plus adesive arround battery to secure all cells!..
Is is better to use holders or save some dollars on some holders and spend money on insulation cards, plus hot glue, plus adhesive?

Any way even using cell holder, u could separate cells ,not with insulation card, but with some temperature insulation element. In case of random cell thermal runway, it will not spread heat to surround cells!

Anyone has safe ideas to build batteries?

 

[batteryGOLD]

& also careful about "iBMS's" / smart BMS's with BT app.
most chinease apps installed @ phone have permissions to Ur phone files and other phone system permissions..

Careful when installing ANY app at you phone! learn about online security, do not install crazy apps

 

[rafalg]

Ah ok. How long did it burn for? Trying to figure out how long my battery would burn for, if it goes bad and I have it in the barbecue where I am going to keep the actually build within.

First few cells burned quite violently with flames clearly visible, then it calmed down a bit and next cells just sizzled and smoked for longer time. I left it there for an hour to be sure nothing more is going to burn.

 

[batteryGOLD]

don't trust any cells.. pyrotechnic stuff is not 100% trustable.. careful
there is just a 0.03% chance of igniting battery.. but depends, it could rise to 1% or 20% or 100%! depends on how U use it

do you trust at Sony made in Japan cells or U prefer china cells?

 

[Cyclomania]

do you trust at Sony made in Japan cells or U prefer china cells?

I do like em both I have to admit