Battery draining Battery drains after a day

Have you been able to determine what is causing the battery to drain ?

HELP 2000 Z3 Battery Drain - Bimmerfest - BMW Forums

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Feb 18, 2007 - 7 posts - ‎6 authors
HELP 2000 Z3 Battery Drain E36/7 Z3 (1996-2002) ... Something is draining the battery. ... Posts: 55. Mein Auto: 2000 BMW Z3 2.8 Roadster. z3 1.9 battery drain (fuse 31)
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Starter and alternator are the most likely culprits(one day). Interior lights and radio will also cause this. But usually takes a couple days to drain the battery.

This problem may be a drain or a bad battery or alternator.

The first thing to do before going on trying to find the system that is draining the battery would be to have the battery tested and charging system tested.

A weak battery will seem ok after the car is jumped or will barely start the car and the alternator will charge it even though the alternator is overworking due to weak battery and during the day or when car does not sit long it will seem ok. then when car sits overnight or a few days battery will weaken on its own, making it look like a drain,

so first step is battery test and alternator/charging system test.

See battery from all sides,check battery waterhose r compleatly packed or not

You may have a parasitic drain on the battery.
Check the voltage on your fuses after you turn it off. Wait 5 minutes before doing so.
Hook up an Amp meter in series with the battery and see what the current draw is. If it is more than 250 milliamps you have a parasitic drain.

heater resistor's cause battery drains and air con operate incorrectly.

Sometimes the battery itself is the problem. The quality and age plays a big role. Best way to test is to disconnect the battery cables from the battery after your done using the car. Then a day or so, hook the battery back up and then see if the problem still occurs.

If the battery drained, you'll know the battery itself is the problem.

aftermarket stereo? dome lights? car alarm? Use a multimeter and see what fuse has power draw when car is off.

No, corrosion will not cause a battery to drain, even if the corrosion is on the terminals. Several factors can cause battery drain, I would first have the battery tested to see if the battery it self is not bad. If the battery is good, then the most common is a short. All most all new cars have a certain amount of drain,(measured in milivolts) this drain is for clocks and computer memory's, and it would take several days of a vehicle sitting for the battery to be drained. Don't immediately assume you have a problem if you see 2-6 milivolts of drain on a battery with the key out, now if your battery is being drained after being parked over night, you have a problem. The easiest way to pin down the problem short is to disconnect your positive battery cable from the battery, take a 12 volt test light and clamp one end to the positive cable, and hold the probe to the positive post. Now if you have a short the light will come on. Have someone help you by pulling the fuses one at a time. If when a fuse is pulled the light goes out you have isolated the short to that system. If you pulled all the fuses and the light never went out try disconnecting all the wires from the alternator, 9 times outta 10 do this will let you know where your short is. If the system is not critical like power locks some people just leave the fuse out.