What's that battery in the trunk?

[Tiger]

I am wondering what is that battery in the trunk? Is that for the alarm? I am finding the alarm is acting so bizarre... in the morning, the alarm will not unlock the car. Start it up and back it out into the street to park... then later in the afternoon, the door will unlock for me with the same damn key.

Key battery is new. This saga has been going on since I bought he car... but recently is really something. I also know that lead acid battery don't last that long either... this one is 14 years old.

So I am wondering... is it this small battery in the trunk the real main reason why remote doesn't work when we needed it to be? Where do I buy this battery?

[attack eagle]

huh? what small battery in the trunk?
got pictures?

What alarm?

[Paul in NZ]

any battery place should be able to match it...I took mine(and the related holders and relays out)....no ill effects.Battery was completely dead,previous owner didnt even know it was there,and at one time there had been an acid spill,cos the boot floor was completely covered in baking soda..(under the carpets)

[Tiger]

LOL... you didn't even know... on driver side... behind the cover and just above the wheel well.

I am going to investigate anc change it out. I think this would solve the stupid key problem.

Alarm? Factory installed alarm.

[repenttokyo]

LOL... you didn't even know... on driver side... behind the cover and just above the wheel well.

I am going to investigate anc change it out. I think this would solve the stupid key problem.

Alarm? Factory installed alarm.

my car does not have this battery either.

[Tiger]

Strange... I know mine has it... it is near the factory amp. Small white battery. Paul has an 1989... and mine is 1994... so that means you guys should have it...

Do you have factory alarm system? Or factory keyless entry system?

[repenttokyo]

Strange... I know mine has it... it is near the factory amp. Small white battery. Paul has an 1989... and mine is 1994... so that means you guys should have it...

Do you have factory alarm system? Or factory keyless entry system?

no on either count.

[Tiger]

maybe that is the reason why you don't have one.

Eagle... I don't have factory cell phone either... so it is not related to cell. I want to do an experiment with that small battery... replace it and see how the key remote works and if it is consistent solid performance.

[attack eagle]

yeah because my car doesn't have one... which means it is an add on.

the only battery I am aware of that could be oem fitted would have been the second battery option from the e32

[attack eagle]

did at one point.

my suggestion? Dump it completely.

Those batteries have a finite life cycle and they turn into a big electrical drain/load after a year or two when they stop holding a charge.

Do you have a factory Cell install? perhaps it is related to that.

I was in there on a loaded 92 535i on labor day and it didn't have it either.