Power will come from two sources:

• From the 12V line, available at the lighter. Only available when the scooter has it's ignition on. Connected to the arduino DC jack.
• From the battery, 65v to around 84v power supply. I'll be using a DC/DC bring it down to 5v. The connection will be made at PA3 connection, which is the ignition connector. And will connect directly to the 5V VCC at the arduino.

The battery power line will have a NO relay connected to it that will be closed from the arduino itself. This will allow the arduino to completely power off in case of low battery. It will come back to life when the ignition is turned on, by the 12V.

Meanwhile, since we're tapping the ignition line, lets add another relay (NC now), that will be used to remotely kill the scooter, in case of emergency or if stolen.

One thing I'm in doubt is if the arduino prefers to be powered from the DC jack or from the 5V. Probably won't be an issue. The rest of the logic will be always powered from the battery via DC/DC.

By the way, the DC/DC will be a 110-230V power supply that I tested and provides 2.5A from at least 48VDC to 96VDC.