XSeries-forum

Hi all. I've got the e53d x5 and for the past 6weeks the battery keeps going flat. But not strange thing is it will be ok for a week or so then all of a sudden it gos flat. I can drive to the shops leave it half an hour come back to it and it's flat... Then it will be ok till it decides to do it again. Each time I've had the as come out who have tested the battery and altinater witch are working fine. Just seems as if the car has a mind of its own. Has anyone had this problem or any ideas what could be causing this. Thanks Wayne.

Mine was similar to your problem, in the end I changed the battery to a Bosch S5 and that cured the problem, I was also told that the battery was ok, and in summer it probably would be, but in winter is was just not good enough.

Phill

Any indication as to how old you battery is? If it's more than about 5 years then it will in likelihood need to be replaced. I went through the same odd behaviour on my 2005 X5, and had to replace the original battery in December 2010 - 6 years after the car was built.

Another possibility if your battery and alternator both show as OK, is that your starter motor may be faulty. This is also a known issue with these cars. I had to have mine done under warranty when the car would quite suddenly not start (very slow cranking), but had been fine shortly before. It took BMW a while to find it but when they did, the starter was actually drawing more current than the battery could deliver so causing the voltage to drop, electronics to reset and the car just would not start, but the battery itself was fine. It needs a specialist to test it as you need access to a special 'current clamp' to read what the starter is drawing. Mine was well over 800 Amps!!!

The battery is only 8 months old but what's seems strange is that it will start after being left for a couple of days then after running around in it park it up for 30mons then gone to start it and the battery is flat said something has quickly drained it. Jump the car and it's fine till it decides to to it again wether it takes 3days or 3 weeks.

Are the connections tight? If they are then unless the battery itself has gone faulty - which can happen - it's unlikely that's the cause. Connections between the battery and starter worth looking at too.

When it fails to crank properly, are all the other electronics affected? Mine used to throw spurious error messages and cause the systems to go into a reset mode and wipe the history in the OBC for fuel economy etc. All down to the starter fault dropping the volts to about 9V and cranking very slowly. It was completely random as to when it did it - but very annoying!!

Nothing at all just clicks. I've made sure everything is tight as when the as drop tested the battery he checked everything. Just seems strange how is fos it every now and then. And it can drain the battery within 30mins

Have you access to a voltmeter which can tell you what the real state of the battery is? It should be between 12.4V and 12.6V fully charged. On charge, you should be seeing around 14.4V from the alternator.

If there's not enough in the battery to crank, that suggests a bad cell, or bad starter/solenoid. Nothing else in the way. As you say, to kill a battery in 30mins takes some doing! Being random will make it a bugger to find too, although there may be an error code being logged by the car.

To find the drain, you'll need to place an ammeter into the circuit between the -ve pole of the battery and the lead itself. Don't try starting in this state, but if you have a meter capable of reading say 30A then you can step down the range until you get a meaningful reading. With the car asleep, I think the draw is less than 120mA.

A thought that has just occurred, are your AC fans all shutting down when you switch off the car? I've never experienced the symptoms, but might this be a FSR failure? Someone who has suffered a FSR issue will know.

The FSR could be the cause, but I would be surprised if it would kill the battery in the space of 30 minutes. If the FSR is at fault, other clues are the Air Con doing odd things - e.g. not working at all, or the fan speeds blowing full blast irrespective of what speed is set.

[quote=""Tizzard.""]Hi all. I've got the e53d x5 and for the past 6weeks the battery keeps going flat. But not strange thing is it will be ok for a week or so then all of a sudden it gos flat. I can drive to the shops leave it half an hour come back to it and it's flat... Then it will be ok till it decides to do it again. Each time I've had the as come out who have tested the battery and altinater witch are working fine. Just seems as if the car has a mind of its own. Has anyone had this problem or any ideas what could be causing this. Thanks Wayne.[/quote]

how do you know its the battery that's goin flat? have u tested with a volt meter or are the other electronics failing as well? or is it just that the starter wouldn't crank?

cos your symptom if its just the starter not cranking at odd times could very well mean not a bad battery but bad solenoids in ur starter motor.

You need to eliminate the battery first, check the battery voltage while cranking the engine if the battery drops below 10volts its shot. if the battery is good it sounds like you have a high resistance across a connection (poor connection)

Mixed results might be achived by placing a voltage reader across each fused whilst sat in car after it shuts down,however, a pro diagnostic from a competent indy is the way forward.

ULF failure on factory phones on older models can be an issue but it could be any one of a number of issues.

I see comments re possible significant drain based on it not starting after just 30mins, however, if battery already tired it might not take much drain to cause battery to drop below what's required to turn the starter.

If it were me the car would go to an indy albeit it is important to find a good one with decent kit & competent at such diagnostic work on the E53.

Does sound very familiar to what I went through for about 5 months with mine. I would actually be driving along and the whole car would start to shut down. I'd pull over and turn the engine off and when trying to restart it would be completely dead. Wait 10 minutes and then it would start up straight away and be fine. Could go weeks with nothing and then it would do it again. Other times the battery would just be totally dead after being stood for a few hours and would need a jump start.

Had battery replaced and other components checked etc on many different occasions whilst sat at the dealers for diagnostic checks. The battery and alternator were always showing as ok when checked at the dealers and roadside each time but in the end I managed to get them agree to change the FSR and alternator under warranty. Never had an issue since and its been over a year now.

Change the FSR in the first instance if it were me as that is renowned to be an electrical nuisance on these. If still an issue then consider a faulty alternator.