17500 Problem

[dca2]

I was checking my BOB and discovered these:

Pos End

Neg End (the pics are arranged with the cells in the same order left to right--I am concerned with the one on the right)

They were stored charged in a small ziplock-type bag, side by side, pos. up. My BOB typically stays in the back of my car and has seen 100+ temps and ~20 Temps. I have 2 more identical cells that were in a Wolf Eyes Raider in the same BOB and they show no bad marks. The cells are about one year old and have about 3 cycles on them. Ideas?

My WE Raider also has some weird corrosion on the exterior. Related?

Thanks for any insight,
Dave

 

[SilverFox]

Hello Dave,

It looks like your cell vented.

When expecting temperature extremes during storage, it is better to undercharge your cells before storing them. Charging to 4.05 or 4.1 volts should keep that from happening in the future.

Tom

 

[dca2]

I am guessing the vent happened last time they were in the light? I did not notice the damage to the cells and charged them on a DSD charger. It was only this morning, 2 months after charging, that I saw the discoloration and corrosion. There is no discoloration or damage to the inside of my Raider.

Raider inside body tube

Raider inside tailcap
Only corrosion is outside tailcap

I should mention that the cells were not in the Raider, nor were they close to it when I noticed the damage. Cells were inside the BOB and the light was in an outside pocket of the BOB.

 

[VidPro]

looks like the right one in the pics , is the one that popped, the left one just has residue from the top of the other one.
you know to not get that stuff on your skin and all, right?
cause your freaking touching it , wash your hands

is there any denting or impact damage on the dead one?

 

[dca2]

looks like the right one in the pics , is the one that popped, the left one just has residue from the top of the other one.
you know to not get that stuff on your skin and all, right?
cause your freaking touching it , wash your hands

is there any denting or impact damage on the dead one?

Slight buldge at the top:

(I knew about the hazards--I wore gloves earlier and the cases were then cleaned--no residue was on the cells)

 

[VidPro]

they are protected, from what it looks like
in this picture AW17500side.jpg is that a thin melt or burn line down the side? (or just a reflected shadow).
the protected cell has a metal strip that runs From the opposite pole to the protection curcuit, you can see on the good one the slight bulge line under the insulation.

on the Bad one, is there melting down that strip line?

 

[LuxLuthor]

Slight buldge at the top:

(I knew about the hazards--I wore gloves earlier and the cases were then cleaned--no residue was on the cells)

LOL...you look ready to do some Ebola virus testing.

 

[VidPro]

Did it vent IN or out of a light? CSI style

the residue on the bottom of the other cell would indicate that the cells were together stacked top to bottom.
Witness claims are that the batterys when out of the light were side by side, not stacked top bottom.
IF they were together in the light, then the venting location would be somewhere in the middle of the "all too clean" tube.
if you removed the battery without noticing the venting, got caustic materials on your hands, and subsequently, touched the tail cap of the light to screw it on or off.
it Might be consistant with the oxidation looking damage on the tailcap.
adding, if you didnt know you had transfered costic electrolite to the tailcap, it would have the time to eat away slowly at it.

that just leaves the "mystery" of the clean tube.
it was a minimal venting, more caustic electrolyte and less solid materials.
the way the 2 batterys would "stack" and the vent hole location, would still allow stuff to escape out the side.
sooo, the tube could be clean because of a coating that is less effected by the caustic materials, like Oiley, or plastic coated, or enameled, or similar.

 

[SilverFox]

Hello Dave,

It is good to see you taking safety precautions.

I can't seem to find the article I was looking for, but it discussed cold weather charging. One of the problems was that the voltage of Li-Ion cells would increase when going from cold to warmer conditions. The RC people have had problems with this in warmer climates in the summer. They have burned their cars up by charging their Li-Po pack up in a cool office over the lunch hour, then placed the pack in a warm car getting ready to fly after work.

When becoming curious about what all the commotion was about and why there were fire fighters in the parking lot, the employee discovered that his car was totally involved in flame.

The cause was never determined, but speculation suggested that the battery pack was out of balance bringing at least one cell to a dangerously high voltage level, and the 30+ F increase in temperature was enough to bring it to a runaway condition.

I thought there was a chart that showed the change in voltage with respect to the change in temperature, but I can't find it.

Tom

 

[DM51]

This is an intriguing thread with some very interesting and useful information.