The Batteries are switched manually using the toggle switch as it would be unsafe to automatically switch between them (the circuit is designed to utilize break before make switching). As the voltages can range from 42 to 59 volt between a full and flat battery, a direct connection between the packs are not reccomended and can cause fires at worst or shorten the pack life. This circuit uses relays to perform the switching and is not controlled by the microcontroller at all. The arduino simply drives the status LEDs for each pack by measuring the voltage on every cycle.