Low and Critical Battery Voltages

Different wireless device types define low and critical battery state voltage levels independently.
Device Type
Low Battery
Critical Battery
4.6V
4.3V
4.5V
4.0V
4.5V
4.0V
4.7V
4.5V
6.0+ volts is considered to be the maximum value, or 100%.
To calculate battery percentage:
percentage = (batteryVoltageOrMaxPossible – criticalVoltage) / (maxBatteryVoltage – criticalVoltage) * 100