What's a good way to track down a battery drain?
 

The problem is not on my P-car but in my brother's Alfa Spider. He's replaced his battery once already and now, the new one is already dead (less than 2 months old). Does anyone have a shortcut way to track down what's draining his battery? I thought measuring the voltage while idling to get a baseline then shutting it down, pulling a fuse, then restarting and remeasuring would be a good way but that would take a long time. Does anyone know a better, surefire process? His car is a garage queen (it gets driven maybe 1500 miles a year only). Thanks.

You need a good amperemeter to check if there is any current when the car is not running. If there is start pulling fuses until you have the branch located that draws current. Sometimes wrongly wired stereo equipment (amplifier that does not power off) are the culprits. If nothing else helps he should get a trickle charger to maintain the battery in case the car is not driven often.

Just to be sure I would also check the voltage when the car runs to make sure you are not dealing with a dead regulator. This would cause the battery to constantly overcharge and loose its capacity.

Good luck,
Ingo

Charging voltage off-idle should be in the range of 14+ volts. Depending on the system load during operation (fan, electric FP, electric motors, lights, etc.), a lower charging voltage may not be enough to prevent discharging the battery.

To conduct a Parasitic Current Draw test, connect an ammeter in series between the battery ground post and the ground cable, then follow Ingo's procedure.

Hope this helps,
Sherwood

Thanks guys. I knew I could get the help I needed here.

This has been posted before, but you may want to try this...

remove the cable from the negative terminal of the battery and put a multi-meter between the cable and the battery ( car not running!). Measure standby milli-amp draw ( set scale correctly on meter if necessary). Start removing/ re-installing one fuse at a time until the draw goes down. The problem will be in THAT circuit. Now...trace all the users on THAT circuit until you find the culprit.

Wil

Thanks Wil. I've got a feeling it's the car stereo that he had Good Guys install two years ago that's causing the drain.

It's almost always aftermarket stereo or alarm guys.....hackers !!!

Wil