Hi.
I noticed, that my Lii-500 is overcharging some 18650 cells.
New/old no matter.
Some are terminated, others are charging 5000, 6000mAh @4.2V and getting hot.
All slots, no difference.
Is it cell or charger issue?
Mike
I’m gonna say charger. It must terminate at 4.20V. If it’s doing what you described with known good cells it’s the charger for sure.
Note that 4.5V is only a very small step away from thermal runaway, fire and explosion. You should discard these cells.
I tend to agree. Most chargers are <$30, does not pay to mess around.
Maybe old batts .Measure resistance. But …charger shows 4.5V on screen? Whats not normal. Have no protection? Probably both time to trash.
4.2, sorry fat fingers.
I had overheating problems with old laptop batts , if so, you know what to do.
You can’t pump more current into the batteries without raising the voltage. So if they’re sitting at 4.2 V, all you see is either bad batteries (very high internal resistance) or a problem in the charger (it can transfer heat via the charging contacts into the battery).
Can you check the voltage with a multimeter? Maybe the charger doesn’t measure correctly.
Does a charger measure the current to the battery?
As batteries age the fully charged resting voltage will drop, i have some cells that only charge to 4.14v and that may be triggering the charger to keep charging so the charge cycle goes around in a loop which will just make the situation worse.
Problem diagnosed and solved.
Nothing wrong with charger.
3 of 5 VCT6 cells were faulty. After no more than 20 charging cycles. Bought from reputable local company.
So I need new cells.
Mike
1 Thank
Interesting
Fake or Old — High heat and Extreme cold will ruin cells — I have some VTC6 cells around 6-8 yrs old with that still test 95%
If they are using the constant Current/Constant Voltage aogrithm they have to. During the constant voltage phase they need to sense the current to determine charge termination.
2 Thanks
Sorry for your loss 
And VTC6 batteries have a good rep from what I can see, which makes it quite puzzling.
I would try and let the company you bought from know, at least it should be an important data point for them, and perhaps (if besides reputable they’re also friendly) they will offer you some kind of ‘consideration’ (eg replacement batteries or at least a discount on buying new ones).
I was thinking red sanyo heaters.
Stay at 4.2v and get hot.
Bad cells