WHY DOES MY BATTERY KEEP GOING DEAD

ozzyhufc · Post by **ozzyhufc** » Tue Apr 17, 2012 8:31 am

After every few days i dont drive my X5 the battery goes dead, its a new one plus i have change the headjog unit as i was told it could be that , plus altenator has been tested so thats ok check boot lights they ok, has anyone had the same thing happen, after about 3-4 days car wont start, i just went away for 10 days on holiday when i went to start X5 there were not even any lights on dash its was dead flat, once been runing 10/15 mins every day its ok, please help!!!!!!!!!!!!!!!!! its doing my head in

scooby1doo1 · Post by **scooby1doo1** » Tue Apr 17, 2012 8:53 am

Did you get a genuine FSR are an eBay copy, are you getting the FSR none faults. Have you changed replace or added any leki items.

My battery just went flat a few weeks back now, but was caused by FSR keeping the fan on a low speed.
Replaced with gen BMW item and all is well.

Sent from the Iphone via talktapa

X5Sport · Post by **X5Sport** » Tue Apr 17, 2012 9:36 am

Sounds like you may need a battery test done. How much of this you can do yourself depends upon what tools you have. This assumes that the replacement FSR is OK. Running a car for 15 mins a day is not enough to keep the battery charged. It takes approx 20-miles to put the starting charge back into the battery. If you are only doing short journeys the battery may not ever be getting properly charged.

Otherwise.....follow as below..

You can either get the battery 'drop-tested' (they don't physically 'drop' it so don't worry) by any car workshop to see if it's holding a charge or.......as below.

A simple battery check is to fully charge the battery - ideally overnight - and then leave it for four hours to allow the charge to settle down. Whilst waiting out the four hours, pop the bonnet and relock the car - if safe to do so where you live. This means that the alarm switch is already in the right position and you can lift the bonnet without 'waking' the car again. After 4 hours (without unlocking the car and working from under the bonnet) measure the battery voltage at the jump start points. It should be around 12.6V DC. Anything below 12V is beginning to show a problem, and below 11.5V means knackered battery.

Check it again several hours later to see whether it has dropped at all. If it does then things get more complicated. You need to eliminate the battery or the car as the problem area. To check the battery you need to disconnect it in the boot and leave it. To check the car you will need a decent multimeter with a maximum current capacity exceeding 10A DC for this. Have the meter set to display the current in the 10A (or higher) DC range. Don't use AC current. Then read on......

You need to get into the boot and at the battery and loosen the negative battery cable - do not remove it yet. Make sure all the doors etc are shut.

Connect the Positive lead from the meter to the car body.

Connect the Negative lead onto the negative battery terminal - this might need the battery cable moving to accomodate you, but try not to remove the battery lead if possible. The meter lead connection needs to be secure as it's going to be left in place for a while.

Now lift the negative battery lead away. This means the meter is now acting as the negative return path to the battery and you can read the amount of current flowing.

Don't shut the upper tailgate so that you have access to the meter and battery. It also means if the leads drop off you can still get into the car or at the battery easily!

Wait for the car to go to 'sleep' (about 16 minutes or so), all the interior lights to go out (you should be able to lock the car beforehand), the little LED by the 'P' on the gear shift to go out and then see what the meter readout is. If you have an auto-ranging one it will look after itself, but if not you need to wind the range down manually.

If I remember correctly the 'sleeping car' current is less than 130mA. If it's much higher than this then you have a 'parasitic draw' from something and will have to start pulling fuses to find it. To do that you will need the passenger door open, glovebox lid lowered and access to both the front (and rear) fuseboxes. You will need to pull the fuses one at a time (make careful note of where it came from so you put it back in the same slot) until the reading drops.

This is the only way I know of to check for battery power leaks. It does take time, but if you do it yourself it will save you the labour cost of a dealer doing the same.

If the readout is correct, leave it for a while to see if the car 'awakes' on it's own - the tell tale LED will come on too.

If nothing changes then the chances are that you have a bad battery.

ozzyhufc · Post by **ozzyhufc** » Tue Apr 17, 2012 10:04 am

i have replace the FSR with new bmw up graded one and the battery has been tested and r all ok, this is what bugging me what can it be!!!!!!!!

X5Sport · Post by **X5Sport** » Wed Apr 18, 2012 8:46 pm

In that case you may need to look for a parasitic draw.

Also get the starter motor checked. The SM is a known problem area and the fault usually manifests itself by very sluggish starting. This is the result of the starter drawing more current than the battery can sustain and so the volts drop, that causes the computers to reset and gives all the appearance of a dead battery.

What voltages are you getting when metering the battery?

jonnyivy · Post by **jonnyivy** » Sun May 06, 2012 11:42 am

Just noticed this thread,.... Mine done the same several weeks ago,... wasn't a cold morning or frost,.. just that the battery didn't have enough power to spin the motor fast enough to fire up. Didn't want the hassle of dead battery so I went and bought a brand new one. However, 2 days ago when I went to start it, I thought it seemed rather sluggish to turnover. Yesterday was worse ,.. it just died when I turned the key. I walk to work all week so don't use the car, but surely a car should last more than a week without draining the battery ?
Ended up just jump starting the car (off its original battery which I found out had nothing wrong with it ) and after a few miles down the road was full of life when trying to start again when I got home.
Jonny

X5Sport · Post by **X5Sport** » Sun May 06, 2012 11:54 am

My E53 did the same and in my case it turned out to be a faulty starter motor. It was trying to draw so much current that the battery was unable to provide it and the voltage dropped. This is another 'known'' problem for E53 owners unfortunately. It took the dealer 5 attempts and blaming all sorts of other things from door locks and mirrors to the tracking device (which they then wrecked) before the real cause was found.

It only happened on cold days and once the car had been warmed up was fine. As with yours, leave it a week and it would not crank, but the battery was absolutely fine.

To 'prove' it you need to use a device called a 'current clamp' which needs to be capable of reading up to 1,000A. Mine was drawing around 900A if memory serves. The normal maximum is around 800A for a cold 30d engine.

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