When cells get old, do they get more dangerous or less?
State all necessary assumptions to support.
I’ve got several that are probably below 60% of their original capacity.
I just wonder if they pose any special risk , other than not working all that well.
wle
More or less. There is a difference between a worn out cell and a defective cell.
An old cell has reduced capacity due to the aging component of degradation. Over time the cell will degrade even if not used, and especially if left fully charged. This is not a dangerous condition.
Another capacity degradation can occur due to high usage, i.e. high number of cycles. i would call this normal wear and tear that uses up the cell—it is just worn out. Not dangerous, but less useful if the full capacity is required.
Another factor in capacity degradation is related to temperature of both storage and operating conditions.
A defective cell is another issue altogether with respect to risk and danger.
The main cause of cell failure is loss of electrolyte, and this can become a dangerous situation.
Damage and defects can be introduced by incorrect usage and charging protocols. This becomes dangerous.
Damage and defects can also be introduced by improper assembly and substandard materials. This is just poor quality and short cuts by cheap vendors, and is a dangerous situation.
I scalped a pack from an old Dell (that I owned from new…) and all of the cells were 000 according to my Craftsman multi. All 6 of those cells are sitting on my bench. I intend to recycle them but are they little bombs waiting to go off?..….
Uh… REALLY “absolute zero” That sounds very odd as I have pulled batteries (still in use) one from a 2003 Sony laptop I also owned since new. But there was over 2v on those batteries pulled about 5 years ago.
If absolute 0… I’d toss them and not try to mess with DEAD. The only Li-ion batteries I’ve got zero readings off were some Chinese “knocky-offies” I dead shorted in a project (nothing smoked, but it all got HOT and I left it 24 hours or so to cool down in the back yard) Those were definitely DEAD the next day.
i had serval cells that would not even register on DMM, oddly they came from laptop pack, half of cells were totally dead, like open circuit dead, other half had 4v, and were pretty healthy
[spam removed]
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That looks like an open circuit reading of the meter, i.e. no real voltage was measured. My meter reads 0.000 with nothing connected.
Some cells have an internal protection device to open the circuit path in the event that the cell gets too hot, others will open the circuit device if the internal pressure gets too high.
Dell wouldn’t want any fires to spoil their rep, so they may have a self discharge mode to drain the pack in the event of any cell issues. The BMS chip in some Ryobi packs has this “feature”.
So they need to be recycled; they are likely okay to sit on your bench, but it is not worth the risk to try to reuse them. If you attempted to recharge them, then that is what could set them off.
To charge old cells is dangerous. They heats up and……
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We lived near the Willamette for 6 yrs.
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I tend to work on the principal that if they don`t get warm when charging then they`re safe, if they do, then it`s time to discharge them, thank them for their service and recycle them.
things i learned so far:
warm charge = bad
loss of electrolyte is a common cause of capacity loss = can be bad
( i was assuming no physical damage, or bad charge/discharge damage - just normal use )
thx
wle
Yes, and also check to see if they’re warm when just sitting idle (after charging). I’ve had a couple of heaters do that (fairly new Samsung 30Q). Turned out they were suffering from very high self-discharge, dropping about 0.1v per day. They felt slightly warm to the touch. Must have been a small internal short. So, definitely in the unsafe category.
How old is old for Li-ion? My oldest are 3yo.
also i would add “the charge that never ends” - though if i am not mistaken, cells that do that, are also getting hot
though heating may depend on the charge current…
wle
Green wrapped cells and all dead. I did put one in a xtar X4 and the meter read 0 so I pulled it immediately.
These are 10+ yrs old.
…Love the Willamette
i would also suspect that “0 volt” cells are really cells whose protection circuits have disconnected
probably due to the real voltage being under some “do not charge these any more” threshold like .9v or 1.0v
wle
I`v had that a few times with NiMH batts, I tend to get the opposite with Li-ion, they can be really low, put them in the charger and they`re at 4.1v in less than a minute! they`ll read full but hold almost nothing, sometimes i`v even wondered if someones swapped the insides with a 10180 cell LOL
As a general rule, I would refresh my cells (meaning buy new ones) every 5 years. I do the same with car batteries. Yes I know they will last longer then five years but following this basic rule ensures you always have new batteries. At $5 a pop, its not that much money even if you have 20-30 cells.
yes that is another symptom of being worn out - the too-fast charge and low capacity
i think my phone battery is doing that
wle