battery drain?

[Majikal]

I bought a brand new battery for my 91 318i recently, and it was working great. Its not my daily driver, so I left it in my garage for a few days untouched... upon returning and trying to start the car, no crank, batterys dead. What could be draining the battery when the cars off? And even when the cars running, as the battery drains the car shuts off, so is there an Alternator problem? I dont even know where to start with this problem.

[NC325iC]

its usually the obc and radio memory, also if you have a flashlight in your glovebox thats draining it too, as well as anything plugged into the cig lighter, if your gonna leave you car w/ out driving it put a trickle charger or disconnect the battery

[Majikal]

really? Is that just the way it is? I took out my OBC and replaced it with a gauge so thats not it. I dont understand how the radio memory can drain an entire battery in a matter of days, how can it suck so much power? Jeez!

[mattdk318i]

if you have an aftermarket stereo. Id check for wire shorts. lots of times they get crammed against the heatercore and they tend to rub

[Majikal]

nope, still factory stereo. Dont know what to do, no lights are being left on, like the glovebox or trunk or map lights or anthing... I cant figure out what it could be!

[NC325iC]

my car used to eat batteries for breakfast, i donno why do a test on it

use an ammeter btw the ground lead (connecting batt to car) and the battery (yes you must unhook it) and start pulling fuses one by one and when it changes or goes away you found your circuit

[smonkbmw]

you said you checked it BUT. i had issues with both the trunk light and the glove box light. the glove box didnt shut all the way everytime, you could see the light through the cracks.

[Majikal]

Ill double check again, shit Ill even unplug em. lol

[AndrewBird]

Get a voltmeter and check the voltage at the battery WITH the car running. Should be above 12V but no higher then 14V. If it's lower, then the alternator isn't charging.

To check if there is a power drain, hook an amp meter inline with the positive battery cable. If there is a reading, then there is a drain. To find it, start pulling fuses and when the reading goes away, you know what circuit is causing the drain.