David Farber wrote:
With the unit powered on and no load or signal, the draw was about
545ma.

About 6.5 watts... that seems reasonable.

In standby mode, the current draw was about 4.5ma.

This shouldn't kill a car battery in good condition. I have heard
various numbers for the acceptable "key off" draw on a car battery but
20 mA is usually somewhere in the ballpark. This is for everything in
the car - the radio station memory, a clock, anything the ECU needs,
security system, etc. 20 mA is 0.48 amp-hours a day, or 6.7 Ah in two
weeks. A car battery is very very roughly 50 Ah plus or minus [1]; with
6.7 Ah gone it will probably still start the car. ("Airport time" is
one name for this - you should be able to leave the car at the airport
for X amount of time and it should still start when you get back.)

I'm going to reinstall the radio tomorrow and see how these numbers
compare to the current drain from the car battery.

You might poke at the harness side of the connectors with a 12 V test
light before you reinstall the radio. Maybe it's not getting the
message that it could go into standby - short to battery power on the
"hot in run" line?

If this car has any aftermarket stereo equipment wired to the factory
head end, you can assume this was done incorrectly and be right about
half the time. Other sources of automotive electrical fun include
aftermarket trailer hookups and driving lights.

If the car has a trunk light or underhood light, look to see if it's
shutting off correctly when the trunk/hood is closed. This can be
a hard-to-catch source of battery drain.

Matt Roberds

[1] Yes, I know they are not rated by their manufacturer or sold this
way. If you use one like a deep-cycle battery instead of a starting
battery, you get roughly 50 Ah. Yes, it's not a good idea to use a
starting battery like a deep-cycle. The 50 Ah number is just there
as a reference for things like this.