I’m looking at avionics, engines & batteries Some of Garmin’s items ask for 14/28 volts. Rotax’s website & the 915ISC discusses an electric starter of either 12 or 24 volts. Then at the bottom the same engine states it has a 24v power supply delivering up to 800w. I’d like to go with the EarthX ETX680C battery which is rated at 13.2v. So my question is, do I choose 12/14 or 24/28v? Probably a rookie question but I know enough about electricity to get a good shock.

My best guess is that I will have a 12v system. But what dictates this?

Thanks in advance,