Monday, 30 June 2014
If you don't have a computerized charger to confirm the amount of capacity, another good indicator is to measure the open circuit voltage (no load voltage) of the pack or individual cells right after a flight/drive with a digital volt meter or other similar digital voltage measuring device. An 80% discharged LiPo cell, will give an approximate open circuit voltage of about 3.72 to 3.74 volts. A 3S LiPo pack therefore would show about 11.2 volts after a flight when it's about 80% discharged, a 6S pack would be in the 22.4 volt region. The longer you wait after the flight/drive, the less accurate this voltage method of determining an 80% percent discharge works because as the pack rests after the flight, the resting open circuit voltage recovers slightly, perhaps up to 3.76 volts or so. Remember, states of charge in any battery are based on capacity, not voltage for the simple reason voltage drop in a battery is non-linear.