1 dead battery..... and now another.....

[Sweetride01 10+ year member]

Ok,

I'm currently living in Cardiff, Wales (working for Fram, so I can answer any questions you have about filters). My '90 325iS is still at home in Florida, and my mum drives it every 2 weeks. The alarm is left off. I have 2 USAmps IS2150 running comps and sub.

Amps are run to the battery in the trunk. My audio system (iirc) was left turned off at the HU (So its not playing when the car is driven). The car is driven about 15 mins every 2 weeks (as far as I know). I had an Odyssey 925 battery in there, been in there for about a year. Not heavily used. Every time the car was started it was apparently fine. Then, 2 weeks later, COMPLETELY dead. Nothing works. My mum said she got a charger for it, but after talking to some ppl, including my mech, she replaced it with a large HD battery, without telling me (thats bad 'cuz the Odyssey was still under warranty). So, this new battery has been in less than 3 months, apparently fine crank everytime it's started, then BAM, the battery is completely dead again. So My mum will be calling Odyssey and this other battery company, and hopefully getting replacements.

Any ideas on why this is happening???

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[phyphoestilic 5,000+ posts]

alt is not charging as much as its suppose to?

 

[Curel 10+ year member]

If the car is only driven for a little while every 2 weeks, then your battery will run down when not in use. You need to put a trickle charger on the battery when not in use or drive the car every few days so the alternator can charge it up.

 

[Sweetride01 10+ year member]

Can't you usually leave a car in storage for like 3 months though and still have a battery that will crank? And, when it is driven 2 weeks before, wouldn't it have a weak crank? .....Perhaps my alternator did go. Oh, thats right, just before I left, I drove with the BMW club at high speeds, and I accidentally did an (8000?) RPM downshift. Something also sounded a little funny. I suppose that could kill an alternator???

 

[Curel 10+ year member]

There is still a very small draw from your vehicle when the car is off. disconnecting the battery might help, but might not be good for the car for ex: pcm might need to relearn itself, radio presets will be gone, etc.

It is possible that your alternator is failed, but usually 95% of the time the battery light will come on when the alternator is under or over charging.

Run the car for a few minutes every few days and you'll be fine it sounds like.

 

[jdawg 5,000+ posts]

get one of these

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93258

tell your mom to take it to the mechanic and wire it up to your battery, it wont overcharge, its automatic