I left my Morserino-32 switched on overnight and was able to replicate the effect: my battery is now down to 1.8v. I have a couple of prototypes at home, so I was able to splice in a replacement and the Morserino-32 now works fine. I had a word with Willi about this effect and this is what he wrote back:
the problem with LiPos is that they do not like deep discharging… I think this is the first time that I hear this happen with a Morserino, but in general, deep discharging a few times will damage the batteries, so that eventually they need to be replaced.
Unfortunately the electronics on the Heltec module prevent overcharging, but not deep discharge .
May be it would be in order to include a warning in the manual…
I did a deep discharge 3 or 4 times on one of the Tattu batteries, and it is still working ok (maybe with slightly diminished capacity).
So, it seems like there is a possibility that the LiPo can be deep discharged if the unit is not turned off at the main switch. Willi is going to update the manual, but in the meantime, Morserino owners should take it as read that the unit should always be turned off with the slide switch when you are finished. If you do accidently over-discharge your LiPo, the Morserino-32 will still work fine powered from a portable USB power source.
In all instances, Willi is always happy to receive ‘constructive’ feedback (in both English and German). Please contact him by email if necessary.
73 de OE6FEG