PinePhone Developer edition

[wibble]

How can I revitalize it?
Does the PinePhone do trickle charging if powered off?

I'd hope that the PinePhone would charge the battery when off, but can't say for sure. Your best bet may be a universal external charger - they're fairly cheap and handy to have around anyway. They've usually got spring contacts with adjustable spacing. At a push you can use a bench supply if it has an adjustable current limit. Either should let you get enough charge into the battery to start the phone.

The battery datasheet is in the wiki now, including the schematic and board layout for the protection PCB. The contacts aren't explicitly labelled but if I'm interpreting the pcb layers correctly the 4 terminals are as follows, starting with the one closest to the edge of the battery:

• V+
  
• thermistor
  
• V-
  
• n/c
  

I've just spotted the + and - markings in sharpie on the battery connector in this photo which look consistent with that.