Battery safety?

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joshludden

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Had a pretty violent crash this morning & kinda dinged up my battery (see more of the destruction on my frankenbuild thread😆). Is this thing safe to use anymore? I'm hesitant to even put it on the charger. I just don't have enough knowledge/ experience with lipos to confidently do either so any input will definitely help. Thank you all in advance

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I'd be too scared to use it too.
 
I'd be too scared to use it too.
Yeah I didn't even notice the damage to the battery when I unplugged it because almost all of the parts that were destroyed and/or lost were on the opposite side!🤷‍♂️ Sooo glad that it didn't go up in flames!! Just got done building it yesterday & it was about a quarter mile away when it lost traction & crashed 😬🤔
 
Whats the worst that can happen?

charge it outside, on concrete, keep it out of the house and go for gold? I've got a couple dinged up batteries too but I keep them out in the garage tight in their storage bag.
 
If there was anything wrong with that battery it would have already gone up in smoke. I've used lipos that looked much much worse than that. Hell I had a couple that looked like bananas for a few years.
 
It's hard to tell from the picture if there's damage to the cells or if it's limited to the case. This is unfortunately the worst spot for a battery to take damage (edges of the cells) because crushing a cell here is most likely to create an internal short circuit and render it dangerous. If you can do it safely and without further crushing or puncturing the cells, strip back the heat shrink and check their condition. If they're noticeably damaged I would junk it. If they're not, I would keep using it (wrap with tape to hold the casing together) but quarantine it away from other good batteries and monitor it closely for any issues related to charging, balancing, elevated self-discharge in storage and increased internal resistance with any of the cells.

One important thing to keep in mind is just because it didn't burst into flames immediately, this doesn't necessarily mean it's not at a higher risk of doing so now. Most often these batteries if damaged will go into thermal runaway during or shortly after charging, as discussed on pages 57-59 of this report:

Mechanical abuse of cells can cause shorting between cell electrodes, leading to localized cell
heating that propagates to the entire cell and initiates thermal runaway. The mechanical abuse
can be severe and result in immediate failure, or it can be subtle, and create a flaw in the cell that
results in an internal cell fault much later (i.e., after the cell has undergone numerous cycles).

...

Mechanical damage (crush or penetration) that occurs at electrode edges is significantly more
likely to cause cell thermal runaway than damage perpendicular to electrode surfaces
(Figure 32). Exponent demonstrated this susceptibility by conducting crush tests on cells in
differing orientations. When crush damage is perpendicular to electrode surfaces, it may deform
the electrodes and separator layers, but it may not cause penetration of the separator, and thus,
minimal or no internal shorting occurs (certainly, if the separator is penetrated, shorting and
thermal runaway can occur). If the cell case is penetrated (e.g., during a nail test), it is likely that
low impedance shorting will occur between current collectors bridged by the penetrating nail,
and cell heating may be too low to result in cell thermal runaway. However, if crush or
penetration occurs perpendicular to electrode edges, that deformation is likely to result in high
impedance shorting between electrode layers and initiate cell thermal runaway.

...

If mechanical damage does not cause cell thermal runaway immediately or within hours of
occurrence, it can still cause cell thermal runaway if the cell continues to be cycled and used. A
point of mild mechanical damage can become a point of electrode or separator degradation over
multiple cell cycles. Ultimately, severe lithium plating (another root cause that may have the
potential to result in cell thermal runaway) occurs at the point of degradation, or a significant
hole in the cell separator develops, so that during or after cell charging, the cell undergoes a
thermal runaway reaction. Failure by this mode, like most cell internal shorting failures, is most
likely to occur during cell charging, or immediately after charging (mechanism discussed below).

...

Failures due to latent mechanical damage have prompted certain precautions taken by electric
model aircraft (i.e., radio-controlled aircraft) enthusiasts. Lithium-ion pouch cells have long
been favored by this community due to their light weight. However, because these cells are not
enclosed by sturdy cases, they are very susceptible to mild mechanical damage, and routinely
exposed to potential sources of mechanical damage. Fires during charging of these cells are very
common even with cells that do not appear significantly damaged. Thus, enthusiasts have
learned to expect that fires will occur periodically and recommend charging cells in fire-safe
areas or containers such as fire safes, fire places, and sand pits.

...

Exponent has observed numerous field failures caused by latent mechanical damage, particularly
of soft-pouch cells where mild mechanical damage did not cause immediate failure, but rather
failed during subsequent cycling. Exponent has conducted testing to attempt to determine
whether specific levels of mechanical damage will ultimately result in cell thermal runaway
reactions. We have found no nondestructive way to definitely rule out a future cell failure.

...

To prevent fires from occurring due to cell mechanical damage, it is important to quarantine and
monitor cells or packs that have suffered mechanical damage. Mechanically damaged cells and
battery packs should then be disposed of, rather than placed back into service, unless extensive
studies have been carried out specific to the cell chemistry in use and the degree of mechanical
damage experienced, to show that the damage did not induce a defect likely to cause cell thermal
runaway. Should mechanical damage exposure be suspected but not confirmed, the suspect
batteries should be quarantined, during and after, all subsequent charging processes. Packs
should be monitored for excessive self-discharge rates and charging processes should be
monitored carefully for evidence of cell internal shorting (noisy voltage signals, extended
charging times). Any evidence of poor behavior should trigger proper disposal of the battery
pack.

Possibly more than you wanted to know, but I think it's useful information.
 
Thanks a bunch fellas! I'll definitely keep an eye on it. I stuck it in a lipo bag and put it on my concrete patio while I'm out of town for the wkend. No rcing for me this weekend 👎
 
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