Cells get warm, or not - TP4056 vs iMAX B6 vs Opus BT-C3100

MajStealth

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Apr 11, 2017
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i notice a strange thing while charging and discharging used cells

while charging and/or discharging them with the opus or imax, like 90% of cells get at least somewhat warmer, some quite warm, not yet hot, but warm

strangely, while charging them in one of my 7 tp4056+protection they do not get warm at all, even ones i know get quite warm when charging

all 3 are rated to charge/discharge at 1Amp

the tps are charging, i checked it with the opus and imax, multimeter has a dead cable.... just 1 week old....
tps are powered from my pc-psu atm, a dedicated one is already laying here after modification of the internals, waiting to get some connectors

what am i missing here?
 
Good Q. They do stop at different stages if im not mistaken. Perhaps thats the issue? Just guessing though that the other that get warm top it off a bit better and therefore stress the cell a bit more.
 
hmm both the imax and opus stop at 4.2v and decrease the amperage from 1A to 0.1A and stop after that, still, the cells are already warm when getting there

to begin with, i am used to the fact that cells get warmer when charging, NiCd and NiNm both did this in the past - so i am a little bit confused that jehu says they shouldnt get warm what so ever
 
My understanding is this heat is totally dependent on the internal resistance of each cell ... an old cell with an Int res of 160m Ohms will generate 4 times more heat on charging (or discharging) than a new cell with 40 mOhm Int res , if charged at the same current.
 
However, if one charger is charging at .8amps, and the other at 1amps, that can make the difference as to whether it generates noticeable heat.
Or, if the IR of the cell only really effects it when it reaches, say, 4.17V @ 1A; if one charger drops from 1A to .8A at 4.16V and another drops from 1A to .8A @ 4.18V, then the one that is holding the 1A for the longer duration will get hotter.

In my experience, I've found that in the same charger, a cell can get quite warm. Pop it out, discharge slightly & leave it for a few days, drop it back in, and it doesn't get warm again. What's going on there!? Did the IR change in the cell? Is the charger working differently on that cell than previously? Did the last charge happen to snap off some dendrites that were forming? ???????

Further review is definitely required
 
definately had that last thing kori states, one day they get warm, another hot and in the third run they are as cool as the room - not logic in it.... but i also had 2 other sorts of cells, one got hot as fu.. and got like 20000mah in charges but must have spent that in heat, while others where capable of holding 5, yes FIVE mah^^

btw the 20k mah charge happened in the imax with tempsensor attached
 
I have noticed the same thing. Also, the cheap 2-cell wall wart chargers NEVER seem to heat a cell, and they also top them up much closer to 4.2V than does the opus. The latter can quite happily tell you the cell is full at 4.09V, which then can be topped up to ~4.19V with the wall wart. I have also shelved charged cells at 4.13V, only to find quite a while later that they have crept up in voltage to as high as 4.18.

image_wjczuc.jpg
 
Cannot compare to the types of chargers used, but i recognized that my cells get heated up only if i charge at 1 Amp. At lesst some of them do heat up. Usually i personally go with .5 Amps during the inital phase and sorting. No issues then.
However, i noticed that weak cells get sometimes hot at even .5 Amps.
 
What I have seen with the tp4056's is they start to reduce the current right away. So for example when the voltage gets up to 4V it's already starting to slow down to .7A and as the voltage goes up it slows down proportionally. Where Imax or RC chargers keep it at 1A (or what ever you set) until it reaches 4.2V then starts slowing down the Amps to keep it at 4.2


This generates more heat in the cell. Which is not a bad thing as it reduces internal resistance (IR) in the cell as it warms up. Now to get a proper reading you should let the cell Cool down for a set time then discharge

Hope this helps
 
Have also found that working a bit with "heaters" sometimes restores them to working state. Maybe some dendrites do indeed dissolve with heat.
 
thanar said:
Have also found that working a bit with "heaters" sometimes restores them to working state. Maybe some dendrites do indeed dissolve with heat.

It's not actually "dendrites" that are growing. It's the chemical composition of the electrolyte. Other threads have discussed this and I came across several articles where they specifically tested these types of cells.
The electrolyte goes through a chemical change and some of the components separate slightly causing a type of oxidation layer on one side of the electrical film. When charging, it forces the bonds to reconnect and the chemicals are reconstituted back together and the oxidation layer goes away.
That's why the cell will get almost fire hot when charging (especially above 4.1V) on the first run, and then consecutive runs it doesn't get as hot. Sometimes it takes 2 runs, sometimes 5 (arbitrary numbers, could take less/more cycles). It just depends on how much the chemical bonds have separated.
 
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