Safe temperature for charging 18650 cells

I have a Foxnovo 4s Digital charger and I noticed that some cells are charging a lot hotter than others.

Is there a recommended max temperature for a cell being charged at 1 amp so that decide which are bad and which are not? They do charge up to 4.2v and most are rated at 2000+ mamps on the discharge.

becarefull the red ones .... ( sanyo ) get really .... extreme hot ! ... you must be gentle with this ones....( 500 mah ... charge or discharge )

If you can't hold it comfortably with bare hands then it is too hot. Most cells don't exceed 35C while charging at 1A.

if you cant leave you finger for more than a few seconds, too hot. take them out and let them rest for a day or so. then you could retry them. some cells will get hot after sitting for a long time. afterwards they are fine. i have several like this. but dont let them get hotter than 40C

I generally do the hand test. If I can set my hand on without thinking "oh that's hot", it's fine. That being said, everyone's threshold for heat/pain is different.

I've had quite a few situations similar to what Korishan said earlier. Some cells (often red Sanyo, but not only) get hot when I first try to charge them up to 4.2. I take them off the charger and give them a day or so and retry at a lower current. Many will then charge fine. If they still get hot, I bin them. With the ones that charge OK on 2nd try I normally do a discharge/recharge to see if the heating is a recurring problem. If they are OK (don't get hot), then I'll test them for capacity.