2007 BMW 525 - Charge issue

i got new battery few months back. i didnt drive the car for a week and car wouldnt start. jump start worked and battery shows as 94% charged within an hour of keeping engine running. i use the car everyday but it didnt start again after a month. i feel some components draining battery. could it be an alternator issue or how to check battery drain?

Shops that sell batteries have sensitive instruments that can test battery drain (and a lot of other things) without breaking open the circuit. That would be my first suggestion.

If you want to do it yourself, you will need an inexpensive volt-ohm meter, and I suggest a 12V power supply that you can plug in to the power outlet (cigarette lighter) to keep the car powered while you pull off a battery cable. The reason to keep it powered is because the car will forget a number of things if it is powered down - seat and mirror and radio settings at a minimum. If memory serves, this car will forget a number of other things, like the full open and closed positions of windows and sunroof. Whatever it forgets, you will need to reprogram after the test. Much easier to use a 12V power supply.

I don’t know where your battery is, but the first place I would look is below the floor of your trunk in the passenger side.

The actual ‘home’ drain test involves pulling off a battery terminal clamp and putting the amp meter in series between the battery terminal and the cable clamp. Then go get a cup of coffee because it will take 10-15 minutes for all the computers to go into sleep mode so you can measure the drain. Historically, the rule of thumb was 30 milliAmps to 50 milliAmps was acceptable and would allow the car to be parked several months. I suspect on this car that a little more than 50 milliAmps will be normal. If you are flowing over 100 milliAmps, something is not turning off as it should. Start pulling fuses one at a time and see if the current flow rate drops.

You should wait at least an hour to make sure all computers/modules have gone to sleep.


Hey, would using a battery minder (temporary power supply plugged into lighter) screw up an at rest power draw/leakage test?

Some cars with a lot of electronic gizmos might start running low on battery charge after a week of not being started. The result would be a fails to crank, you don’t hear the normal rrr rrr rrr sound with the key in start. Is that the symptom?

Why would anyone do that?


No, what I mean is if somebody is putting an multimeter between battery and positive cable to check for power draw after engine turned off (parasitic loss, like above), would leaving the the memory saver plugged into the vehicle during the test process screw up the results?

That little 9 volt battery will have no effect on a parasitic draw test on the main battery.