(05-02-2016, 11:38 AM)tkaiser Wrote:(05-02-2016, 11:35 AM)clamum Wrote: So it sounds like I'd need a DC-DC step down converter like you or rahlquist posted, and a battery (like this P64 RTC backup battery?)
Nope, in a car you need a stabilized step-down converter and you need a real battery (for the cases when input voltage drops below certain tresholds eg when you turn on the engine). Pine64 has a real battery connector not just for the RTC.
Thanks tkaiser, forgot about the inherent vast fluctuation in voltage in vehicles.
EDIT: A fairly comprehensive piece on this subject.
http://www.carnetix.com/regulators/how_t...e_psu.html
Overall I was just not thinking earlier. What you may want to do is find a stabilized supply that outputs more than 5v (say 9v) stable and the use a normal adjustable DC-DC converter for the final tweak since 5.0v may not be enough and you may need a smidge more depending on your situation and the length and quality of wires you use.