Voltage is quite a poor indicator of state of charge (SOC), and with lithium it's even worse than SLA, as there are very sharp drop offs at both ends of the curve. I would guess that 36.9v is between 50-30% capacity remaining.i have the black 13mAh battery...
today after 22 miles ride, i still have 36.9V and it says 3/4 full. I'm finding this
hard to believe
what is the empty voltage for this battery?
If you need accuracy, you need to put a watt meter on it.