Attention users of TTGO21 v1.6 (boards labeled “T3_V1.6” on pcb): During a test run on battery after about 30 minutes the battery exploded and got on fire. Board and battery burned down to nearly nothing in less then 30 seconds.
I used a Li-Po battery 3,7V / 840mAh. It was properly connected to the board, since the board did boot and run on battery. I then connected the board additionally to a 1A USB wallcharger using it’s USB port.
Since there is nothing left after board and battery burned down, i cannot investigate what happened.
But i remember that i wondered about the voltage measurement which was shown by my software, using the voltage divider on board: It showed 5,024 Volt. If this is really correct - and i assume it is - it means that there must be a hardware design error on the board which is causing a direct connection of the battery to USB 5V.