Audis vs Batteries

[rdh@genrad.com (Robert D. Houk)]

Hmmm...what is the plural of Audi? Audis? Audies? Audii?

Anyways, with regard to batteries and key-off accessories and keeping them
topped off -- I find it very hard to believe that the radiator fan (injec-
tor cooling fan; auxiliary turbo coolant pump; etc; and so forth) running
after the ignition is turned off has *any* significant effect on the bat-
tery. I am of course assuming that the whatever do shut off properly, as
I'm certain that a radiator fan running overnight will drain the battery!
And I know for a fact that leaving a [high-powered assault] stereo on over-
night in 10F weather will drain the battery . . . [cough cough]

Assuming that the fan runs a full minute (I've never seen my UrQ run that
long, and they certainly like to run hot), and draws maybe 10 amps (the
whole circuit is [under]fused at 25amps, and key-off low-speed is a *lot*
less power than AC/overtemp hurricane-force), and the injector cooling fan
draw the same (No Way! wimply little motor!), and the fuel pump stayed on
that long (it doesn't!), and the non-existant (on UrQs) turbo coolant pump
ditto, that's still only maybe 50 amp-minutes peak drain. This represents
1-2% of the battery's capacity at most. (More of course in cold weather,
but still a small percentage of the battery's capacity.)

If you have to keep charging your battery, then something is seriously
wrong with your electrical system. Granted with an Audi, that's almost a
given, but still . . . even my UrQ (which must represent Audi's nadir of
electrical competence) idle voltage doesn't drop below 13v until I've got
headlights and fan and defroster and radiator (or windows) running. Of
course that's with a new alternator . . .

					-RDH