Do batteries get hot when charging?

Question

Charger

I got a varta lcd charger 57070 today , put the batteries that are included in the kit to charge. After an hour or two I touched them. And one pair is straight hot burning, the other is warm.
Should I be worried? Ask to exchange the charger, but there seems to be no problem? Or is this the norm?
How, in general, to make sure that everything is in order and works correctly without waiting for something to melt or explode :)?

Answer 1

There is little good in such heating, these are all the costs of striving for "fast" charging. In my "smart" charger like BC700, when the charging current is set to 700 mA (this is the maximum for it), the batteries heat up noticeably, and this is the norm. With more current, the heating will be greater, so if yours can give more current, then do not be surprised.
But the difference in individual channels is alarming. Swap heated and non -heated ones and see where the heat moves. If it remains in the same place, the charger is guilty, if it moves, the problem is in the batteries (they, worn out, may have increased internal resistance).
And one more thing: driving batteries in excessive modes is not good for their durability. So the desire for speed can go sideways.