# 88 735i new battery is dead and now won't hold a charge



## iainlsheridan (Dec 3, 2008)

I bought this 88 735i about 2 weeks ago and bought a brand new battery the night i got the car and then 2 days ago the battery was dead and now won't hold a charge over night. I really need a cheap way to fix this because I can't keep jumping this every morning...Any help would be great:thumbup:


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## TerryY (Jul 20, 2003)

Have the battery tested where you bought it? They should replace it under warranty.

Even if something in the car drug it down it should charge up again unless the battery is defective.


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## iainlsheridan (Dec 3, 2008)

Is there anything that could be draining the power? this is my first bmw and i don't know anything about them, it seems a little odd that after a week the battery dies all of a sudden and then can't hold a charge over night.


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## TerryY (Jul 20, 2003)

If the car is staying awake (odometer stays on) it could run a fresh battery down in a week or two. BUT the battery should take a charge after being discharged like that.

I have had a brand new battery die overnight in cold weather so it isn't impossible that the battery is the problem.


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## iainlsheridan (Dec 3, 2008)

Again i know nothing about BMW's. How would the car stay awake?


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## TerryY (Jul 20, 2003)

The big BMWs shut all the little electronic toys down after it is sure that you are not going to use them again. If you turn the key off and stay sitting in the car you will hear motors running behind the dash for several minutes as everything in the climate system among other things return to their start positions. When all of the housekeeping tasks are done the car goes to sleep to minimize battery drain

If you shut it off and get out in about 15 minutes the lights in the odometer will go off. That is the sign that the car is asleep. You can check the lights thru the windows because opening the door makes it partially wake up. Turning the key wakes it up the rest of the way.

If it doesn't go to sleep then something is not shutting off in the car electronics and it will run the battery down. The E31 8 series is notorious for not going to sleep and running the batteries down. It takes a couple of weeks to run them down but they have 2 batteries about the same size as the one in your 7.

One of the things that I never could figure out was why with all of the fancy stuff didn't they include a complete auto light shut down when everything else had it.


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## M.Wong (Jan 9, 2003)

TerryY said:


> Have the battery tested where you bought it


iainlsheridan, did you start with the basics?

It does happen, a brand new battery ends up being bad. You should start there, then check for a mystery drain.


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## iainlsheridan (Dec 3, 2008)

I know i sound pretty pathetic at this point but how do you check for power drains? I am a PC geek and don't know anything about cars


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## iainlsheridan (Dec 3, 2008)

Is there a way to turn off sleep mode so everything just shuts off when i turn off the car?


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## M.Wong (Jan 9, 2003)

I'd still like to know if you followed TerryY's suggestion first. :dunno:


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## iainlsheridan (Dec 3, 2008)

Well last night I tried to jump the car and nothing so my uncle is replacing the battery now since I am at work, I am assuming that will work but i am afraid that the battery will die again after a week.


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## TerryY (Jul 20, 2003)

iainlsheridan said:


> Well last night I tried to jump the car and nothing so my uncle is replacing the battery now since I am at work, I am assuming that will work but i am afraid that the battery will die again after a week.


 If it dies again you might need to buy better batteries. Nothing in the car should be able to drive a new battery so flat that it cannot be recharged. Even if you left the lights on, the battery should be rechargeable.


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## iainlsheridan (Dec 3, 2008)

well the problem is that there is only one autoshop here in town that carries the battery for this car and i have bought out half the supply in the last 2 weeks, my car did start last night and this morning but i am worried that it might get drained from something else again. how do i test for power drains?


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## TerryY (Jul 20, 2003)

Was the original battery defective? That might have been your only problem if it was.

Measuring battery draw takes a multimeter that does amps. Don't forget to look in the window at the odometer after it has been parked for more than 20 minutes.

You could also just check battery voltage for a couple of days to see if it gets lower over time.


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## iainlsheridan (Dec 3, 2008)

Oh i forgot to mention that, after my battery died now my odometer, temp and fuel gauge are not working


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## ArtieD2 (Dec 9, 2008)

FYI: Here's how to check current draw. Don't try to start the car with this set up:










Place meter on "Amps" and use the proper terminals.


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