Define "Damage"

[Freep]

I've read many times and many places that overcharging,over discharging, high temps and low temps will damage your cells.

But I can't seem to find an explanation for the kind of damage that happens and what the result is. I imagine that heat damage is not the same as over discharge damage.

Can anyone explain the nature of the damage to cells in these scenarios? All I get from google is "it will permanently damage them".

 

[mjbeam]

Assuming you are talking about LiFePO4:

(PDF) Failure Investigation of LiFePO4 Cells under Overcharge Conditions

PDF | The failure mechanism of LiFePO4 cells during overcharge conditions has been systematically studied using commercial A123 18650 cells at a 1C rate... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

 

[Freep]

Assuming you are talking about LiFePO4:

(PDF) Failure Investigation of LiFePO4 Cells under Overcharge Conditions

PDF | The failure mechanism of LiFePO4 cells during overcharge conditions has been systematically studied using commercial A123 18650 cells at a 1C rate... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

Yeah I meant LifePo4. I also meant can someone explain it in plain English. I have found several research papers including that one and as with most research papers, it takes forever to get to the point if they ever do.

 

[ghostwriter66]

So when we speak of DAMAGE what we mean is that when you overcharge - or severely undercharge the little bouncy balls of energy in the LiFePO4 battery starts doing things that it can't ever stop doing ... we call those runaway batteries ... once the damage occurs they will show signs of charging or discharging way faster than the other cells tied to them .. once that happens there is no fixing it .. LiFePO4 is a workhorse but once you break its leg - its done ... #1 killer of LiFePO4 is Heat .. #2 is ppl overcharging them .... It is far more forgiving with exceeding under-discharge limits then over-discharge ...

With all of that said - LiFePO4 is still a mystery to even the scientific and engineering community -- there has been major papers wrote and argued over these devices. I have seen ppl overcharge a LiFePO4 cell to the point that its literally a burner - and the battery was fine afterwards ... and I have seen ppl overcharge by a small fraction and the battery collaspes ... no rhyme or reason ...

 

[John Frum]

I've read many times and many places that overcharging,over discharging, high temps and low temps will damage your cells.

But I can't seem to find an explanation for the kind of damage that happens and what the result is. I imagine that heat damage is not the same as over discharge damage.

Can anyone explain the nature of the damage to cells in these scenarios? All I get from google is "it will permanently damage them".

The general idea is the uniformity of the electron migration path is compromised.
From memory I think these irregularities are conceptually stalactite's and might actually be called that.
Then again it might just be the gummy bears talking.

 

[sremick]

It's sometimes tricky to make the leap from "electricity is just this magic invisible force that travels through objects" to how electricity can reach out and change objects (aside from lightning, although that's not a bad example). And, in fact, electricity often depends on the physical change of objects to even work.

In simple terms, inside any battery there is chemistry and there are physical structures. Rechargeable batteries are unique in that these processes (charging and discharging) need to "flex" both the chemistry and the physical structures back and forth. Nothing ever goes back to 100% exactly how it was after even one "flex" and so even normal usage slowly degrades the batteries over time (that's why every battery chemistry is rated for a certain number of "cycles". You can think of it like the number of times you can bend a coat-hanger wire back and forth before it finally snaps).

Extremes (hot, cold, pressure, vibration, impact, etc) will also damage the physical structure to varying degrees. How that then translates is somewhat of a crap-shoot based on that exact instance with that exact cell. Anything from benign (reduced capacity) to catastrophic (fire). Swelling, leaking, overheating without fire, etc. I have a fire safe at work that I got in just in case due to the work I do around batteries (and a bucket of sand and other protection supplies).