hello, I use the sim 7000g to communicate with another device over the serial interface with a level shifter in between (3.3V <-> 5V). I addition, data are transfered by the use uf gprs (mqtt). That worked for some days, but then the board is not working any more when just powered over usb or by the solar panel connector (5V). I guess the 3.3V supply has blown up. Is there the need to have always a battery inserted? In the meantime I have destroyed already 4 devices and have still not figured out what the reason is.

I now try to use a bypass step down converter to power the device also over the VBAT with 4.2V (Lithium charge-end voltage). On the same way I could recover the damaged boards. Only programming is still not posible (Com port is recignized but a connection cannot be established). Is there someone who can help me?