The eSystem must be wired directly to the battery so that is has a continuous power supply.
The system is activated by the onboard accelerometer in response to movement of the bike. It uses a very small amount of power to periodically check whether it should activate or stay in sleep mode. This power consumption is in the region of 400uAh and is less than the natural discharge rate of the bikes battery, so it will not flatten your battery in any way.
This is the correct way to install the eSystem, and if this continuous power supply is maintained the eSystem will retain all the settings input by the rider. If power is disconnected then these settings will reset to default positions, for example the oil level will return to “empty” and the flow rate will return to “off.” If the eSystem is not wired in this way, and is instead wired through a switched power source, then it will not retain its settings. Effectively the switch interrupts the power supply, therefore connection through a switched source is not recommended.