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Discussion Starter #1 (Edited)
I have had to push my 2003 Beast out of the garage and jump start it 3 times in the past 2 months. The car sat in my garage through the winter (Dec.- mid March), but I did try to start it at least once every 2 weeks. I traveled over seas at one point and didn't start the beast for a 3 week duration.

It occurred to me that the alarm system might be draining the battery, therefore I have been storing the vehicle with out locking the car (and effectively arming the system). I have read about the possibility of intermittent fan usage draining the battery but have not observed such an occurence. I plan to purchase a 3-stage trickle charger to charge the battery and hopefully prevent future issues, but I have a few questions:

1) What are the possible reasons that they battery could be repetitively draining?
2) How can I diagnose the problems (besides taking it to a stealer)?
3) Before I hook up the charger or if need be, replace the battery, what precautions must I take so that I don't blow the amp or NAV system?

Thanks in advance,
Justin
 

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There is always a small drain on the battery (clock and certain other functions). When the battery gets down past a certain point (not sure what it is), it shuts off the all electrical components completely, so as to NOT damage the circuits. Sometimes a SLOW charge will bring it up enough to start.

ALWAYS USE A BATTERY TENDER when not starting your car at least weekly (AND DRIVING SOMEWHERE). And, don't start it and let it run for two reasons. 1. It isn't good for the engine (see Owner's Manual), and 2. It isn't enough to completely charge the battery. It takes over 30 miles of driving to completely charge a low battery.

Battery tenders are cheap ... about $ 40 or less. BMW sells two ... a BMW one (cig lighter connection) and a Mini one (alligator clips). I have both, but prefer the Mini ones. Easy to hook up. One clip (black) to a grounded bolt and one clip (red) to the + terminal under the hood.

And, batteries can be faulty ... even new. That's why there are warranties!
 

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how old is your battery?? to begin with..normally a battery is good for about 4 years, most off us will have it for allot longer but after 4 years the best is gone.
second point is when a battery is discharged it looses a10-15% percentage off his recharging power so iff the car had several flat battery moments its maybe time to replace your one, and live on trouble free....

those battery's arent the cost you know,especially iff you are good again for 4-7 years. i read here several times that its about 170-250 $$ for a new oem one so maybe buy your car a new battery and roll on...

iff your car is stored over a period and you start it once and awhile then its normal that the battery goes flat you know, a good working battery has a current off 12.3V (restmode). a m5 needs major juice for starting, under 11.8V it wont start.

so for instance...:3:

your battery has several flat times....lets say 3, then your battery will have the force off 50-60% off a new one. then you start your car once and awhile,the lost juice used there to start here up, can't be recuped by running the engine for a couple off minutes, so its even lower now in % .then you arm your alarm for another 2 weeks :3:,(0.02V a day i thought) again some loss, and so on..
the margine between 12.3V and 11.8V for start up is a fine line,especially iff the battery is weak allready :M5thumbs:


buy your self a new one and live trouble-free again mate

the gurus will chime in iff i got it incorrect.:hihi::hihi:

:cheers:
 

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Due to the way BMW battery systems "disconnect" when they get down to a certain amount of "low" voltage, I personally don't believe it can't be effectively recharged or nearly recharged (like 95%), if it hasn't been discharged too often. (Batteries are NEVER able to be recharged to their original state. They are "aging" since the moment they are filled with acid.)

Batteries fail for a number of reasons ... like they build up sulfides. This happens all the time, and there is nothing you can do about it (see below). The plates lose "weight" due to the acid bath they are in and the transfer of electrons. There is no way to recover the eroded plates, either (actually, that is what a charger tries to do). Vibration can cause plates (and terminals) to become loose or disconnect completely. Cases can crack and drain vital fluid. Plates can crack from vibration, too.

Believe it or not, you can invert a battery that has filler caps on it. Drain out all the acid, spray a hose inside and rinse it out, and sometimes, sometimes you can recover it. Usually, it's not worth the trouble to try.

Many guys here have had their original batteries for over 7 years, but they have been in cars that have either been driven a lot, or on trickle chargers when not being driven. I have seen lots of posts here of over 7 years, but never 8.
 

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Discussion Starter #5
Well I'm planning to buy a trickle charger for $50 that I saw in another thread: http://www.batterystuff.com/battery-chargers/tender/all/BT-021-0128.html

Regardless, it seems like the consensus is that I replace the battery no matter what.

1. What do I need to know;i.e. how do I do it and NOT blow the NAV, Stereo Amplifier, etc.?
2. How do I access it under the seat?
3. Is the part number for the battery found on realOEM?

Thanks,

Justin
 

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Well I'm planning to buy a trickle charger for $50 that I saw in another thread: http://www.batterystuff.com/battery-chargers/tender/all/BT-021-0128.html

Regardless, it seems like the consensus is that I replace the battery no matter what.

1. What do I need to know;i.e. how do I do it and NOT blow the NAV, Stereo Amplifier, etc.?
2. How do I access it under the seat?
3. Is the part number for the battery found on realOEM?

Thanks,

Justin
BMW sells the same units (same manufacturer), but with BMW or Mini on it. Check their prices, too. (You are a BMW CCA member, right?)

1. Don't know, as I have never done it on my M5, I've done it on many other BMWs, and it has never been problem. You will have to reset your clock, etc. afterwards, though. I have read here that with the battery tender hooked up while changing, you won't lose anything, but, again, I don't know for sure. (Have you done a search?)

2. It's in the trunk, under the mat, near the rear bumper.

3. Probably.
 

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Battery is in the trunk, just lift up the trim and you'll see the cover. 3 nuts- 13 or 14mm I think. Disconnect the ground strap, 10mm socket, then take the cover off, then take off the positive terminal.

I replaced mine with a $90 duralast- 49L is the size/number. Needed to make a plate to hold it in place. ( a tad smaller) FYI- the OE lasted about ~80 months. ...For $170 they have one, same specs, which is dimensionally identical- I needed it immediately and didn't want to wait/

If you are neurotic, you'll pay a lot for a 'real BMW' battery, that is actually an OEM made here in the US. Not the same level of quality as OE.

Plenty of posts- do a search

A


PS Nothing kills a battery like fully depleting repeatedly.
 

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like Ard said.. battery in the trunk, pull up the carpet and you will see a black plastic piece with a ///M on it.then wait a minute or 2 ,because the navcomputer must be in restmode and not spinning before unhooking the battery. in the meantime dont open anything or the nav unit spins up again...once it stopt, you can disconnect the battery safely. on the right side you can open it up, its the ground wire(bolt nr10), remove that, then the whole plastic panel, 3 bolts nr 13, remove the plastic, remove the + cable and take out the battery.its heavy so be carefull with your back :hihi:,in with the new one,hook up +cable,put on plastic trim(3bolts nr13),then connect ground wire,put the carpet back and all done ...can't be easyer

atleast 4years good again :hihi:
 
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