my damn battery dies at random times?

[tyro2001]

my car battery will be charged to the fullest at one time and then when i try to start it after like 1 hour or so its dead?
some times i dont start the car for 2 days and it still got juice but some times it dies withen and hour.
could my altenator be working sometimes and sometimes not?
i am really stumped there is nothing in the car that is on when i turn it off.
any help please its really annoying.

PS: i might buy one of those portabale jump pack today

[Gulelin]

I've heard bad things about BMW batteries, but nothing specifically. Just that they are unreliable.

[Trob]

I had an 80 528i with the same problem. Alternator was good and the battery was good. After a couple months of this problem on an off I took a look at the wire that runs directly from the alternator to the positive on my battery. Thier right at the connection it was cracked so if the wire was just right i would be fine ..but if the wire got pushed a little to the side I was getting nothing from the alternator back to the battery. Hope that makes sense and helps. it's a cheap easy fix if its the problem. :P

[broketiltuesday]

Checked the alternator output or drive belt tension?

I had a battery that was a year old when I got my 318 but it died after two or three months of my ownership. I replaced it and it worked fine for about 8 months more until the alternator "failed". By failed I mean it was putting out 12v, enough to run the car and keep the battery topped in normal use but when stereo and blower fans were all going, the lights would dim. The battery needs 13.5-14v across it to recharge/cope with all the accessories going.

Symptoms I noticed but thought nothing of were cranking took a little time (3-4s) on cold days, and sometimes when the car started the battery light would flicker weakly (I only saw this once or twice at night, but it might well have done it when the sun made it unnoticeable). These resolved themselves after I got a reconditioned alternator (mine was an old Valeo which I couldn't find brushes for).

So the alternator could be semi-functional, but is on its way out. Or it could be something as simple as a loose/smooth drivebelt or some corroded alternator/battery connection or earth strap.

[tyro2001]

thanks alot guy i am going to check what you both told me towmorrow morning.

[Numark318i]

did you fill the battery cells with distilled water...cause mie was dry ad it had the saem symptoms....I just filled it up and it works fine.
Just dont touch anything inside of the battery....you prolly know why. Make sure its distilled water

[tyro2001]

the battery is new i got it like 3 months ago

[e30 dude]

are you sure the battery is drained? maybe you just have lose connections at the terminals, or maybe the clamps are rusted..

[CiscoKid]

i park mine in my garage and roll it out to jump start it alot now... i need a new battery. what is a good light battery?