XSeries-forum

Looking at buying a 2005 3.0d sport, The owner has stated the battery does discharge over time (2 weeks) when not in use. The battery has been replace but still discharges. If used daily there are no issues. Any advice is appreciated.
Thanks Mark

Could be as simple as the car not being used enough to fully charge the battery. Need to check the alternator output is good enough.

If it isn’t the simple stuff then it is just possibly part of the car not shutting down properly, poor charging, ‘leak’ in the alternator regulator pack or a parasitic draw somewhere. Finding it will take time and patience. A check with a current clamp with the car asleep will tell how much is being used - it should be less than 80-100mA with lower being better.

Mark1973 wrote: ↑Sat May 23, 2020 11:34 am Looking at buying a 2005 3.0d sport, The owner has stated the battery does discharge over time (2 weeks) when not in use. The battery has been replace but still discharges. If used daily there are no issues. Any advice is appreciated.
Thanks Mark

Normal alternator will take a long journey to fully charge a "low" battery.

First easy step clean the battery connections and ensure they are tight, trace the earth strap and check the earth strap connection is tight to the car body.

If that doesnt help take battery out and charge it fully, at least 12 hours, it may take a lot longer depending on the rating of your charger. If you have a "Smart" battery charger you can just connect it up whist in the car and leave it for a day maybe more. That might solve the problem.

Otherwise there may be battery power "leakage" or parasitic draw. Lots of YOUTUBE videos on how to measure the draw and track it down and fix it.

Or the battery is on its way out and is slowly failing. Measure with a voltmeter after sitting overnight with everything off, and it should read at least 12.4 volts preferably 12.75 or greater.

I had to replace mine recently as the battery constantly needed ( not being used) charging but wouldnt hold a charge.
good luck

Check the charging voltage, it should be be 14.2 volt at 2000rpm +- 0.1volts If low then suspect the charging system and if high it is worth checking for parasitic drain.
If you are doing short journeys then maybe a trickle charger is needed.

Short journeys killed two batteries in my X5 - and one our mini R50. The X5 is rarely running for more than 10 minutes at a time so there's my problem..
I invested in a ctek smart charger and it's brilliant. I've set up the quick plug on mine and I installed an outside socket nearer the cars so I can quickly hook it up. If the car is not going to be used for a few days then it's connected to ensure it will start.

i have the same problem,

Car is going to "sleep"
New Battery
Alternator ok..14.6 volts at the battery when engine running.
Sleep current drain less than !00mA....maybe 70mA
If I leave tail boot open for half an hour...car wont start because battery is gone...even though it has a new one.
I have to battery charge it every couple of weeks or I get stuck on a morning.
Weekly in the winter.
Each time battery goes flat it wreaks havoc with electronics on car.
Last time nearly half my modules lost .
Got some back but still no mid info or TV and many others on pages 2 and 3 of BMW scanner.

BMW's might be great when new but as they age..steer clear.....unless you have a bottomless bank source.

I get about 20 mins from the X6 with doors/boot open before it starts flagging a low battery. The electronics on board draw a lot as do the myriad of interior lights! One issue I have come across is ‘new’ batteries not really being new. The date code is well worth a check as some can be more that a year old when bought, and that can mean poor performance. Checking the voltage on a sleeping car after 4 hours from last use/full charge could identify a failing battery.