Charger pinouts
Charger output - 4.27V (open circuit)
At 3.7kΩ load, charger outputs ~20.4V
Device connected to charger without battery - turns off after a bit
haveged: haveged Stopping due to signal 15
signal 15 -> SIGTERM
20.4V, peak 140mA
Device connected to charger with battery
20.04V, idle 41.1mA
Some funky power signal
https://featherbear.cc/UNSW-CSE-Thesis/posts/serial-dump-during-4-wire-power/
https://featherbear.cc/UNSW-CSE-Thesis/posts/serial-dump-during-2-wire-power/
