I like the volt/amp displays people used…
On my electric Schwinn scooter I use a wireless unit and it works great. You just need a 5 volt usb
power supply to power the display - so no cables!
The newest ones have even a 24 inch long temperature probe installed on them, which would be great
to control our batteries temperature in flight.
On the display you enter the Ah capacity of your battery and it shows the remaining Ah’s in use.
My idea is to put it on a flight deck or directly to the harness like here…