Hi, I received a dead multipurpose (relatively new) Lithium Ion battery pack from my brother who is a test engineer for brushless garden equipment.
The pack contained 20 Sanyo 18650 (UR18650RX) batteries in which two had clearly failed. (Bubbled and deformed)
The remaining 18 measured 0 - 0.14 volts, dead flat! I proceeded to charge the remaining batteries in my Xtar - Vc2 (In a safe place).
They have on average charged to about 1350mah So far so good, no overheating, explosions or general weirdness. I have plenty of other decent batteries, but wanted to let you guys know :)
I doubt that each cell is protected. In the big packs like that they usually just have one protection circuit that protects the pack as a whole, not the individual cells.
I have heard that too. But is it always true? I assume there are two ways the cell can go to 0v. Number 1 being that it is self-discharging due to health issues. But number 2 would be an external influence ran it down to 0v. For the second case I imagine it could be just fine if it was a quality cell to start with. Anyone agree or disagree?
overdischarging then charging can cause internal shorts that may not show up right away, they can catch on fire just sitting there or under use later, i would keep them outside!
those are a somewhat safer chemistry(not li co)
but it is still not good to do!
i have seen datasheets that stated that <1v is a do not charge even with newer safer chemistries.
and the fact that something bad happened to damage some cells means recycle it now.
The fact is that when li ion cells are overdischarged the copper anode dissolves into the electrolyte, then when brought back above 2 volts the copper ions precipitate where they are, not on the foil where the copper belongs. This leads to internal short. Thermal runaway can happen during charging or thereafter with increasing risk if the cell continues to be cycled and used.
Irreversible physical changes have taken place in the cell.
An overdischarged cell is an electrically abused cell.
These damaged cells may continue to function, but with increased risk of failure (including rapid dissassembly).
Don’t Really see the harm,he’s a test engineer so likely well aware of what he’s experimenting and any associated danger.
The op has already stated his intention is to use them “I don’t intend to use them.
It’s just an experiment. I will check the voltage drop from month to month”
As long as he’s taking precautions in case something should happen to them and stores them ideally outside away from the house then I don’t see the problem.
The world and this forum would be a much poorer place if people weren’t curious and didn’t experiment.
People do far far worst and often totally pointless things to these cells, he just wants to see how they hold a charge over a few months for his own curiosity, can’t see any harm in that, personally I’d be interested to see how they hold up.
Whilst it’s a very good idea to warn people of the dangers, - especially inexperienced people -
Of these cells, if people relentlessly hammer the point ever time someone mentions li ion cell, it rather losses it effectiveness especially to the very people who relay do need educating on the dangers of these cells.
Just my opinion of course
This is not the cause of the risk, the danger is that below 2.5V chemical changes happen that can lead to crystal growth over months or years of normal functioning then suddenly the cell explodes with no warning. There is no known way to measure this without taking the battery apart months or years later by someone with the equipment to examine it microscopically
The first indication that your brother isn’t sufficiently well informed is that he gave you a dead lithium battery pack. Or, maybe he didn’t know it was flat and assumed you would know to recycle any zero volt cells rather than charge them. In any case I would not assume someone else’s knowledge base when it comes to my own responsibility. The warnings are there because of real risk. You can’t see inside a cell or test it to know whether or not it’s about to fail, all you can do is follow the guidelines regarding treatment of abused cells and whatever the cause, zero volts constitutes abuse.
