I have bought a few of these (similar ones, not exactly this offer, just the same boards) TP4056 Li-ion charger boards, and I attached Li-ion cells out of an old laptop battery pack to them. I charged the cells up to 4.2V with these boards, which worked fine and then started using it. So, recently the battery was low, so I wanted to recharge.
I plugged the USB into a 5V phone charger, and left it there. I got back to it a few minutes later and noticed that the charger LED already went off. However the blue charging complete LED did not come on. I measured the voltage on the battery, and well nothing much had changed. However, the board was so hot that it melted the 3D printed enclosure it was in, and also burned my fingers. The battery did not get hot or even warm.
I have two of those with the exact same setup, same project etc. and they do the exact same thing. Start charging, stop ~20sec later and start heating up. Tried different phone chargers, tried my computers USB source... Nothing changed.
It may be noteworthy that I have modified the boards by desoldering the red charging LED and attaching a 3mm red LED to the outside of the 3D printed enclosure, but the LED works fine and I don't think this would make a difference.
What could have happened here?
