Another parameter for cell testing?

O

Oz18650

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I was thinking about cells getting hot during charging.

I was wondering if checking how much power has going into the charger for a cell and comparing with the tested capacity would be worthwhile?

If cell A takes more power than cell B (and they both measure as being similar capacity), could you say that cell A has a problem and should not be used?


Presumably a cell that gets hot is wasting the power gong into it as heat.
 
As far as the charger is concerned, it's going to dump power into the cell. If cell A turned 10% of it's power into heat, and cell B stored 99% of its power, and they were both started at the same time, the charger isn't going to know the difference. It's going to think they are both the same capacity.
The only way to know that more heat was generated from cell A is to use a thermister and monitor it during it charging and keep track of at what voltage it got hot at and for how long. Then take the average heat during that time frame and you might be able to do some fancy math to determine how much 'capacity' was converted into heat. Then you might be able to see if cell A is truly bad or not compared to cell B
 
Korishan said:
As far as the charger is concerned, it's going to dump power into the cell. If cell A turned 10% of it's power into heat, and cell B stored 99% of its power, and they were both started at the same time, the charger isn't going to know the difference. It's going to think they are both the same capacity.
The only way to know that more heat was generated from cell A is to use a thermister and monitor it during it charging and keep track of at what voltage it got hot at and for how long. Then take the average heat during that time frame and you might be able to do some fancy math to determine how much 'capacity' was converted into heat. Then you might be able to see if cell A is truly bad or not compared to cell B
Click to expand...

I was thinking that measuring amount of power consumed by a tp4056 charging a cell and then comparing that to the capacity found by discharge testing could be interesting.
 
That could be an option, too. It would be interesting to see what the results would be.

However, that would only work if the cell was fully discharged when it's put into the TP charger. If it's at 3.4V, and the discharger goes to 3.2V, then the readings will be off. Same is true if the cell is at 2.8V to be charged, and the discharger goes to 3.2V, it'll still be off. Even with perfectly good cells.
 
Thats what you test when you look for self discharge afterwards. High self-disacharge = you need more to charge and maintain it. I suppose it should be pretty related.

But doing such a test and then comparing to above would be good.
 
Interesting idea. Even if a cell doesn't get hot. It would be interesting to test none the less. I shall investigate a couple of cells myself.
 
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