What is wrong with my 2003 BMW 525i?Battery Drain

when a battery is completely drained, it shortens the life or could kill it all together. Time for a new one. Doesn't need to be coded.

Most probably it should be a line problem,Need for a right tail light

The oil drain is on the bottom of oil pan off to the side. you will need to remove the lower engine covers to get to the drain plug.

2008?? in my alldata book it says that this is a dealer only job to reset the key fob with diagnostic software ,it is also saying that battery replacement isnt necessary providing it is used at least once a year so it must charge up its own key by the tesla principle ,I cannot be more specific than this as i do not work in a dealership for this type of vehicle

Hi
A car battery can run down for any of several reasons:

• You accidentally left the lights on or some other accessory that pulls power from the battery even when the ignition key is off.
• The battery is not being recharged while the vehicle is being driven (you have a charging problem)
• There is a key off parasitic electrical drain on the battery because a relay is sticking, a module is not shutting down, or there is a shorted diode in the alternator.
• Your battery is old and will not hold a charge anymore. The battery needs to be replaced.

Most of the time if the battery is fairly new and keeps getting drained have the mechanic check the alternator if its charing the battery.
Thanks for using Fixya.

install a battery tender this will mantain the voltage in the battery these work great and will not harm battery or car

www.batterytender.com

have the alternator checked by a shop that is qualified to work on your car.

You might have a parasitic drain on your battery. Meaning something isn't shutting off like it should be draining your battery. Your positive battery cable might be shorted to ground not allowing power to flow.

new altenator,sounds like you put the cables on the wrong way round

If the brake lights are really on (?) this represents about a 4-5 ampere drain that would drag down most batteries in less than a day. (Could be over 100 ampere/hours.)
I don't know your car but brake lights can be controlled by a switch operated by the pedal suspension or a pressure switch that monitors hydraulic pressure in the braking circuit.

If your brake lights are on, the switch that controls them has failed or a relay that is operated by the switch.

If the car seems sluggish or pulls when driven, it could be a failure in the ABS circuit since that is a high-demand (normally intermittant) load.

The best way to locate the problem would be to monitor the current drain with a meter in series from the battery (engine off, monitor the ground side) and pull and replace fuses one-by-one to see which circuit is the culprit.