Intermittant flat battery (E39)

[RustyItalian 11]

All

I've had a 2000 E39 528i for three months and over that time it has drained the battery four times. Sometimes it happens overnight, sometimes while I'm at work. Seems totally random.

All doors are closed and all accessories off as far as I know. No alarm fitted or anything non-factory to draw current.

The battery has a date stamp of 11-08 and appears to be a sealed DIN66.

Any ideas on how to troubleshoot this? Being intermittant it is hard to find a source of the current draw (if that is the cause).

I will pull the battery when I get a chance to check acid levels if possible and have it checked out.

I have jumper leads in the boot and can generally sort it out, but don't want this happening when the wife has it...

Richard

[*Glenn* 854]

20mA is the max currect draw is sleep mode. The most common faults on E39's are the heater fan speed resistor blocks. Do you have all your fan speeds ? and does the heater blower stay on sometimes when the ignition is off ?? If your not sure how to check this, your local sparky can help or we can do it for you.

Edited March 23, 2010 by *Glenn*

[RustyItalian 11]

Thanks for the response, that's the type of head up I was hoping for.

That's the resistor block on the heater module? Common Toyota failure point too.

I have the full climate AC so I'll pay some attention to what it is doing. Will also turn the fan off before switching engine off.

Where's my multimeter...

[*Glenn* 854]

Thanks for the response, that's the type of head up I was hoping for.

That's the resistor block on the heater module? Common Toyota failure point too.

I have the full climate AC so I'll pay some attention to what it is doing. Will also turn the fan off before switching engine off.

Where's my multimeter...

There is a special way to do this and I'm not writing a book about it today. Give me a call and I'll explain

[_ethrty-Andy_ 2132]

V=IR -> 12/0.02= 600ohms.

check your resistances across your battery terminals (removed from battery) if its quite a bit less than 600ohms, pull fuses untill it shoots back up to around the 600 mark. that curcuit will be the one with the leak on it. you can then go from there. thats how i would go about finding a leak

remeber to get the code for your radio/obc if you dont already have it before disconnecting the battery

[*Glenn* 854]

V=IR -> 12/0.02= 600ohms.

check your resistances across your battery terminals (removed from battery) if its quite a bit less than 600ohms, pull fuses untill it shoots back up to around the 600 mark. that curcuit will be the one with the leak on it. you can then go from there. thats how i would go about finding a leak

remeber to get the code for your radio/obc if you dont already have it before disconnecting the battery

Rubbish

[_ethrty-Andy_ 2132]

used sucsessfully multiple times for mine and others. is it because its a late model that its different? will edit if so.

[*Glenn* 854]

used sucsessfully multiple times for mine and others. is it because its a late model that its different? will edit if so.

Correct... its not the right way. The battery has to be connected and you need the car in sleep mode to do it. Its an E39 not an E30

[_ethrty-Andy_ 2132]

Correct... its not the right way. The battery has to be connected and you need the car in sleep mode to do it. Its an E39 not an E30

well ive done that on my moms 05 mazda and a few other late models to sucess, not just my E30. but i guess late bimmers have more systems to go wrong. cheers for the headsup

[*Glenn* 854]

well ive done that on my moms 05 mazda and a few other late models to sucess, not just my E30. but i guess late bimmers have more systems to go wrong. cheers for the headsup

Its not a Mazda either. There is proceedure to diagnose and to test for this problem. Your info is incorrect and missleading

[*Glenn* 854]

Will also turn the fan off before switching engine off.

Turning the fan off will achieve nothing unfortunately

[allan 295]

Glenn is correct turning the heater off will achieve nothing. Should the heater "resistor block" be faulty the heater can have a mind of it's own. The heater blower final stage (resistor block) do fail as they generate heat and over time the resistors inside them degenerate this could be a reason for your flat battery problem, personnel experience.

If I my suggest get the battery checked properly to see what it's state of charge, voltage and ph levels etc no matter how old/ young the battery might be. This is your main power source and if it is faulty it can lead you to have all sorts of weird things happening, E39's have heaps of electronic stuff going on in the back ground.This was my problem when I started having flat batteries. It was not until I removed the battery and had it properly charged and load tested by some one who know what they were doing with batteries that I got a solution to my problem. In my case one of the cells had failed and would not hold a full charge. So if the car wasn't used for a day or so guest what it wouldn't start so frustrating. Best of luck with this and when all cleared up let us know what it was.

Cheers Allan

[hotwire 352]

Wise words!

Just to correct on battery size (from original post) it will be a Din 88/92 (depending on brand) & not a 66.

Also bear in mind when checking current draw - these cars take around 20 min's to go to sleep

[jochen 4]

remeber to get the code for your radio/obc if you dont already have it before disconnecting the battery

No code in the E39 radios. They recognise they are in an E39 and are then happy.

[jochen 4]

Check that the car is properly entering sleep mode: observe autotransimission LED indicator.

It stays on when ign is off, then switches off at +15minutes

When it goes off, car has entered deep sleep (hibernation). This is when current must be <20mA

Opening any doors, unlocking car, activating any devices etc wakes car from hibernation.

[OneStep_TwoStep 21]

Flicking through old threads and might have an answer to this problem if anyone needs it in the future. I had a similar issue with a previous e39. It turned out to be worn wires in the boot flexi hose (where the wires go from the car to the boot lid). They were shorting out and keeping the car from going into sleep mode. $0.50 for some solder and heat shrink and she was sorted.

[jcerecke 2]

I've experienced multiple problems with bad connections on my e39 battery terminals. Will start fine one second, shoot down the road then when I go to start it again nothing. An awkward climb into the boot space and a wiggle (not that my battery terminals are loose!) of the connections/cables brings things back to life and a proper clean of the terminals fixes things.

I get nervous around the e39 battery though, with the huge 12v connector, I read somewhere that there's an explosive in there to cut the 12v line in case of a crash? Freaks me out.

[kiwi535 538]

I've experienced multiple problems with bad connections on my e39 battery terminals. Will start fine one second, shoot down the road then when I go to start it again nothing. An awkward climb into the boot space and a wiggle (not that my battery terminals are loose!) of the connections/cables brings things back to life and a proper clean of the terminals fixes things.

I get nervous around the e39 battery though, with the huge 12v connector, I read somewhere that there's an explosive in there to cut the 12v line in case of a crash? Freaks me out.

explosive?Its probably just the fusible link

[hotwire 352]

Nup, it is actually an explosive device. When an airbag is deployed, it also sets this unit off to isolate the battery for safety. So, in the event of an airbag needing replacement after an accident, so this battery link lead assy needs replacing too, for a cost of course...

[Ahmedsinc 414]

Ha! Trust the Germans to figure how to make an incendiary device into a safety feature!

[kiwi535 538]

Ha! Trust the Germans to figure how to make an incendiary device into a safety feature!

or visa versa!

[aja540i 1906]

Nup, it is actually an explosive device. When an airbag is deployed, it also sets this unit off to isolate the battery for safety. So, in the event of an airbag needing replacement after an accident, so this battery link lead assy needs replacing too, for a cost of course...

That reminds me, i have one of those in my garage somewhere that needs setting off!!

[Allanw 1071]

That reminds me, i have one of those in my garage somewhere that needs setting off!!

Along with that airbag! I've taken two weeks off over Christmas - bring them up... we're less liekly to hit someone up here I know some people who can help with the wounds too.

[aja540i 1906]

Along with that airbag! I've taken two weeks off over Christmas - bring them up... we're less liekly to hit someone up here I know some people who can help with the wounds too.

Im not sure i want to end up in hospital up there, ive heard stories!!

On the other hand we can get an old sofa and a helmet for one of the boys....

[hotwire 352]

Back to the basics,

A DIN 66 is an E36 battery not an E39 battery Its TOO Small to support all the electronics in an E39

E39 should have a DIN 85 or DIN 92

Put the right battery in

Some E39's came with DIN 66. Any with monitors had DIN 85/92. Some no monitor cars too probably. I have seen them with OEM of both sizes