Battery drain

[don 147]

I had spoke earlier about a battery problem, If the car sits for a couple of days the battery is not strong enough to start the car. It seems to be drained. The OBC looses the MPG, time etc. I had the battery checked today and was told it was fine. Where should I look for the drain.
I think that when the car is going to not be driven for a few days, I'll disconnect the positive cable from the battery and see if when i reconnect it if the battery is still charged. If I drive it daily then no problem. Any ideas...

[3798j]

Check this out...It should help.
http://www.popularmechanics.com/_mob...battery-drains
If you do decide to disconnect the battery, it's better/safer to remove the negative cable.

[don 147]

Originally Posted by 3798j

Check this out...It should help.
http://www.popularmechanics.com/_mob...battery-drains
If you do decide to disconnect the battery, it's better/safer to remove the negative cable.

Thanks for the link. Good read.

[jdoublehcubed]

Some people have reported fixing problems like that by replacing the positive cable from the battery. Sounds ridiculous, but I feel like I've seen 4 or 5 people that have replaced it and had a bunch of issues magically cured. Maybe the cable has some sort of smart chip or something in it.

[Taylorguy74]

Whenever I get into my car, I always hear the DVD for the nav spinning up and I always wondered why. I also found out the hard way that after 3 or 4 cyclings of the retractable top, it leads to a no start condition. I plug the car in shortly after any weekend drives and now only take it down on the charger or while running.

My 2008 E90 is always making some sort of occasional bits powering up or down noises, but as it's my DD, doesn't cause anything. Longest I have ever left it alone is about 12 days, and all was still fine.

I read something similar to this article regarding home appliances pulling juice as well even when switched off - ones you wouldn't even think of like a toaster oven. Good read.

[pungo]

I would check the parasitic current draw. Connect a amp meter inline with the positive battery terminal and measure how much current is drawn once the car goes to sleep. Should be 10-20ma maybe a little more. If it's allot more, start pulling fuses until the amps drop and that's the circuit drawing too much current. Troubleshoot that circuit.

[don 147]

Thanks for all the advice, I'll start checking things out. I never power the top up or down without the car running, so that's not the problem. I don't have nav so couldn't be that. I still wonder if its not the battery, don't know but it's a BMW brttery, so it could be the original. They said it checked fine though.

[WAMz4]

A faulty ignition switch has tricked many of us into suspecting a battery drain.
When you turn your key does the instrument panel light up right away, or are the panel lights off when your trying to start the engine?
If the panel lights are off, your engine will not start and you have to turn the key off and back on to get the lights to come on.
This is caused by a faulty switch not turning on the ignition before you turn the key to START position.
This is very sporadic and can happen days or weeks apart so its difficult to catch as your not always looking at your instrument panel when you turn your key.

[don 147]

Originally Posted by WAMz4

A faulty ignition switch has tricked many of us into suspecting a battery drain.
When you turn your key does the instrument panel light up right away, or are the panel lights off when your trying to start the engine?
If the panel lights are off, your engine will not start and you have to turn the key off and back on to get the lights to come on.
This is caused by a faulty switch not turning on the ignition before you turn the key to START position.
This is very sporadic and can happen days or weeks apart so its difficult to catch as your not always looking at your instrument panel when you turn your key.

Thanks, I haven't noticed that, but when it won't start it doesn't matter how many time you try, it just clicks.

[MakSmack]

Looks like I'll be doing this myself. I just bought my M roadster a couple weeks ago. I've been driving it often. Then I left it for a three or four days and it was completely dead.

I still have to ensure that my battery is not to blame, since it's a new purchase and I don't know the battery age/condition/history.

I hate dealing with this kind of stuff...so time consuming.

[StickMon]

Make sure it's an H6.
When I bought mine I found that somebody had put in an H5 ... badly.

[Vanne]

batt should be good to go for a couple of weeks without driving. Mine atm gets driven once a month if lucky and starts fine. no idea how old the batt is, but its gotta be older than 2 years though

[XMetal]

Originally Posted by StickMon

Make sure it's an H6.
When I bought mine I found that somebody had put in an H5 ... badly.

I think even an H7 would fit!