The voltage of Li-Ion cells depends upon their State Of Charge (SOC) - how much energy is in them - and how much current is being drawn. Refer to the chart for a Panasonic cell. The SOC can be estimated by measuring the cell (or battery) voltage.
The Rad battery indicators are simple voltmeters, and are meant to be read with no current draw. This from Rad:
"Check the gauge when the bike is not moving. The LCD display gauge calculates battery life based on the battery power output (instantaneous voltage reading) and can fluctuate while riding if power demand and/or output changes. If you are riding, the battery reading should stabilize at the current battery capacity after about 5 seconds when power assist is off (pedal assist 0 and no throttle applied), the brakes are not activated, and while coasting on the bike."
https://radpowerbikes.zendesk.com/hc/en-us/articles/360006192213
The Rad battery meters are not linear. My chart showing battery voltage vs SOC was made via discharge tests on my Rover 5, and the battery indicator readings determined by substituting a variable power supply for the battery. Note that the bar-type meters can only show a range - for example, 4 bars is anywhere from about 48V to 50.5V, or 50% to 70% SOC.
The Rad battery indicators are simple voltmeters, and are meant to be read with no current draw. This from Rad:
"Check the gauge when the bike is not moving. The LCD display gauge calculates battery life based on the battery power output (instantaneous voltage reading) and can fluctuate while riding if power demand and/or output changes. If you are riding, the battery reading should stabilize at the current battery capacity after about 5 seconds when power assist is off (pedal assist 0 and no throttle applied), the brakes are not activated, and while coasting on the bike."
https://radpowerbikes.zendesk.com/hc/en-us/articles/360006192213
The Rad battery meters are not linear. My chart showing battery voltage vs SOC was made via discharge tests on my Rover 5, and the battery indicator readings determined by substituting a variable power supply for the battery. Note that the bar-type meters can only show a range - for example, 4 bars is anywhere from about 48V to 50.5V, or 50% to 70% SOC.