[lukernie55]

alright so I've been having this problem for almost a year now. The first time i had this problem it was said to be the battery, so we got a new battery. Then it was the alternator so i got a new alternator. Then the new battery failed again so we got another new battery.

A couple months went by with no problems but recently if i let the car sit for a day without using it, it wont start. This morning i went to start it and it seemed like it was trying but just wouldn't start. The dashboard starts to spaz out whenever i try to start it and then the car wont start.

Does anyone know what it could be? I've been through two batteries and an alternator in a year so i really doubt that is the problem, and i don't want to spend a thousand dollars at BMW to get a full electronics check.

Any suggestions are appreciated, thanks

[Red_Bean_Bun]

Did you code the car for the batteries so it matches the ah ratings ?

What batteries did you get for replacement ?

[GoRomeo]

Did you check your starter? Also check your On/Off button do some search on these two...

When you changed your battery did you make sure you did not screw anything up? suchs as the IBS sensor? If this one break car will not start or give you airbag errors

[lukernie55]

Originally Posted by Red_Bean_Bun

Did you code the car for the batteries so it matches the ah ratings ?

What batteries did you get for replacement ?

Yea it was all done at BMW so its all OEM and done correctly

[GoRomeo]

did you read for error codes? You will need OBD reader and cable.

[Braumin]

If your car won't charge while it's running, it's the alternator - that's not your issue.

If your car won't hold a charge, it's either one of two things:
1. Battery is old - obviously not your issue
2. You have a drain on your system when the car is off. The only way I know to test this is to put an ammeter in series with your battery and figure out what's drawing the power.

Back when I was an auto tech, my standard for draw was 35 milliamps or less.

To test this though, you are going to need an ammeter with enough significant digits when on the 10A range (ie it should read 10.000 Amps so you can see the milli scale but still be on the 10A fuse - 10.00 would be OK as well but obviously you lose accuracy).

Don't ever try this on the milliamp scale on a mulitmeter or you'll pop the fuse right away since the car is literally going to draw quite a bit of power (multiple Amps) until it goes into sleep mode.

The obvious question is do you have anything aftermarket installed? I've seen a lot of this with command start installs, as well as some stereo installs where the amp wasn't turning off.

Edit: Here's a link to how to test this: http://www.flashoffroad.com/electric...teryDrain.html