It never did that before. This is a somewhat worn-out Sanyo cell, specced at 2000-ish mAh, some 1500 left in it. It could get slightly warm, 34-36 C, perhaps, but never hot. And the most bizarre is not the fact that it got hot but the circumstances. It was charging at 500 mA, the process was some 30 minutes in, it was nearing the switch from CC to CV. Voltage reading was something like 4.13 V. In fact, I think it might have switched to CV already but I’m not sure. Then I went out for ~50 minutes, and when I’m back it’s at 500 mA and 4.1 V, and the cell is hot. Clearly, it’s not normal for the voltage to go down during charging, the charger should have detected that as a suspicious behavior and stopped charging.
I restarted the charger, let the cell cool off and reinserted it. I discharged it with 1 Amp for several minutes and it didn’t even start getting warm, the voltage was fine as well. Then I charged it with 500 mA, just as I tried before, and it went without a hitch. Does anyone have an explanation what has actually happened? I don’t understand what was going on and why it got warm.
Also, CC/CV charging for 1.2 V cells is a joke, they might have as well said they don’t support NiMH/NiCd at all. It always overheats my Eneloops, so I have to break out Opus for Li-Ion and the good old LaCrosse BC-450 for NiMH, it gets tedious and a waste of time and space to have to fiddle with both. Combine this with significant error in voltage reading, and you may see why I can’t recommend this charger to anyone.