[update: LiLyGo placed the following warning info in banggood.com:
About the lipo charging circuit problem (Important update in 10th September 2018):
After V2.1-1.5 was upgraded to V2.1-1.6, after our tests, the diode components should be used on the charging circuit, but we used a fuse, the diode is unidirectional, and the fuse is bidirectional. This causes the USB voltage to pass directly to the battery. After a long woking time, the battery may become hot or burn, so you cannot use this V2.1-1.6 version to charge the battery! ! ! (Battery can be used, but the battery cannot be charged)
If you want to use this V2.1-1.6 version to charge the battery, you need to replace the fuse in the figure with a diode (Type: BS5819 SOD123 1A) to use the charging function normally. The following is an upgraded picture.]
With SMD diode:
With SMD fuse:
[update: It's offered here in aliexpress]
Verkehrsrot tells us:
"!Attention users of TTGO2.1 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!"
I just received a warning from the TTGO (lilygo store) regarding their TTGO ESP32 Lora v2 1.6 with regards to charging LiPo’s via the 2.1 1.6 board.
Please all be careful.
"Diode components should be used on the charging circuit.
We used a fuse. The diode is energized in one direction, but the fuse is bidirectional, which causing the USB voltage directly access to the battery.
After a long time charged, the battery is hot or burned, so please don’t use this V2.1-1.6 version to charge the battery! ! !
(Note: The board can be powered by battery, but we mustn’t charge the battery when the battery is connected to the board, mustn’t charge! mustn’t charge! mustn’t charge!)
If you want to use this V2.1-1.6 version to charge the battery, you need to replace the fuse in the picture with a diode, then the charging function return to be normal.
It can be changed the model number of the diode : BS5819 SOD123 / 1A current."
"This seems to be a reaction to my post above, i forwarded it to LiLyGo. That means my assumption battery has direct connection to 5V USB was validated by them.
Unfortunately another fatal design flaw and poor quality management seen at a chinese manufacturer…
LiLyGo / TTGO will send replacing diode, if requested, Santos told us there:
I received same mail today.
This is really dangerous. If i would have left the board with battery and USB connected unattended, my flat would probably had burned down. And i used a small 3Wh battery only. That’s far less than e.g. a common 18650 cell…