A 13th battery was purchased today. This bring the voltage up to 156 volts from 144, and the total pack capacity up to 11,700 watt hours from 10,800. This is a 8.3% increase in available energy. I expect to see slightly more than an 8.3% increase in range however. This is because of something known as Peukert’s effect, which basically states that the more quickly you draw energy from an electrochemical cell the less total energy can be extracted ultimately. This holds true conversely; the more slowly you discharge your batteries the more total electricity they will provide. Say I’m traveling down the road at 50mph and consuming 100 amps at 100 motor volts.
Volts * Amps = Watts
100V * 100A = 10,000W
In this case the vehicle is consuming 10,000 Watts of energy. The batteries are not being discharged at 100A as you might expect, as the motor controller acts as a “power converter”. If we have a 144V pack voltage the amp draw from the batteries can be calculated thusly:
Motor Watts / Battery Volts = Battery Amps
10,000W / 144V = 69.4A
So 100A at 100V to the motor consumes about 69 Amps at 144V from the battery string. But now if we increase the battery voltage to 156V by adding an additional battery.
10,000W / 156V = 64.1A
The motor is drawing the same amount of power from the batteries, but because the pack voltage has increased the current required decreases.
