This isnt so much of a question, but an observation…
I have a LoPy4 and Expansion board running on my bench, plugged into the USB on my mac as power source and charger for the LoPy’s LiPo battery.
For the most part it runs fine but the LiPo battery would never go above 3.9V and occasionally / randomly the LoPy would restart and stop uploading data to TTN.
This morning I have plugged it into a RPi wall wart supply and after just 10 minutes the LiPo voltage is reading 4.08V. Time will tell if I stop getting random re-starts.
The point of this thread… Dont skimp on power supplies - it appears to be important.
There might be something else worth exploring… while Pycom have a first-class dev team, the documentation is sparse.
If you are using a LiPo and an external power source (and want to hot swap them whenver) then pull P8 (G15) high (to 3.3V) on the expansion board.
If you also need the SD card, use a 10k pull-up on P8 (G15) to 3.3V.
This all comes about due to some programming automation modes. From what I understand, there were compromises on rev3 of the expansion board that were not well communicated (more features, but some needed external hardware for use).
On my car TTN-Mapper project (which has a LiPo, but also uses external power if available), I haven’t had any issues with charging/hot swapping since I added the pull-up.