On 01/30/18 07:54, Ahem A Rivet's Shot wrote:
> Keeping a pi running won't matter to a car battery.

"Keeping a pi running won't matter to a car battery."

don't be so sure; the capacity of a car battery is only a few tens of
amp-hours.

I recently bought a battery for my car that's rated at 55AH at 20 amps.

Drawing an average of 200ma for a few days can drain it completely, like
maybe an RPi "left running".  Yeah.  This makes a few assumptions about
how good your power conversion is (a switching 5V power supply will be
more efficient than a linear regulator) but you get the idea:

200ma * 24 = 4.8AH ==> ~12 days for 55AH

Also you're really not supposed to go below 50% capacity on a car
battery if you don't want to damage it.  So make that "less than a
week".  Plus there's the "can I start my car when the capacity is that
low" factor.

--- SoupGate-Win32 v1.05