Parasitic battery drain caused by boot lid being closed ~ confused

[reegz]

I have had something draining my battery with high drain warning overnight and usually a dead battery after 2 days, tried some of the various tests inc pulling all fuses to find the drain and come up empty handed, tested for Amp draw while connecting multimeter in series with battery and after car goes to sleep I get just 20 milliamps, left it there and tested battery daily started with 12.69 volts, next day 12.68, day after 12.66 then 12.65. thats a low drain and not what it was doing before so I close the boot lid, lock it and check again in 8 hours,, now it drops to 12.44 volts.

boot lights were turning off however I disconnected them anyway so it seems that when I close the boot something is draining the battery, the switch/latch maybe?

any ideas? maybe someone else has encountered this.

UPDATE:

the 12.44 volts I get while the car is 'awake' when asleep it goes back up to 12.64 so I dont think closing the boot(trunk) lid is causing anything, have driven it a few times so its getting charged up again but now I'm getting high battery discharge warnings overnight, something is slowly killing my brand new battery which also killed the original battery and the previous new battery within 2 months.

[bmwdirtracer]

If you can hook your car up to ISTA, it can tell you exactly what the culprit is. There's a record in the computers. For example, I have a Mini in the shop right now with a major draw. ISTA shows the car is awakening ever ~2 minutes. The maximum number of events (256) is stored; the last fifty show the exact item responsible for waking up the car.....it's an item that is not permitted to wake up the car, but it's doing it anyway: The Amplifier....... You need to connect with ISTA.

[reegz]

oh ok I have not used ista before only Inpa, I will have to source it and have a look. I hope it can register my new battery also (change Ah)as Inpa & NCS attempts dont work

[reegz]

If you can hook your car up to ISTA, it can tell you exactly what the culprit is. There's a record in the computers. For example, I have a Mini in the shop right now with a major draw. ISTA shows the car is awakening ever ~2 minutes. The maximum number of events (256) is stored; the last fifty show the exact item responsible for waking up the car.....it's an item that is not permitted to wake up the car, but it's doing it anyway: The Amplifier....... You need to connect with ISTA.

I got ista+ setup and running and still learning it but whats the best way to check whats using power through the night with ista?

[jclausen]

Boot lid we say trunk lid I believe that's what you mean. It the wiring going into the trunk lid is broken there could be wires touching things there not supposed to also if the car has the auto trans when you lock the car the p light should go out after about 30 mins then the car is asleep. If the p light is not off or comes back on at some point then then some thing has make the car wake up which would indicate a draw. You need to hook up a multi meter between the battery post and the cable and observe the milliamperes after the car goes to sleep.

[ptarditi]

I would check the spare tire well for water or evidence of water, particularly the MPM module.

[reegz]

I would check the spare tire well for water or evidence of water, particularly the MPM module.

I did check the MPM, tyre well was dry and didnt show any signs of water pooling in there, outside of MPM looked clean too, I might have another look and check the terminals

[reegz]

Boot lid we say trunk lid I believe that's what you mean. It the wiring going into the trunk lid is broken there could be wires touching things there not supposed to also if the car has the auto trans when you lock the car the p light should go out after about 30 mins then the car is asleep. If the p light is not off or comes back on at some point then then some thing has make the car wake up which would indicate a draw. You need to hook up a multi meter between the battery post and the cable and observe the milliamperes after the car goes to sleep.

Thanks for the tips jclausen but I had already tried that, checked the wires where they connect into the 'trunk' hinge, I had also tested the battery after the car had gone to sleep and got just 20 milliamps draw, kept coming back to check again was still asleep and 20 milliamps. Its a new battery, second new one actually as whatever is doing it killed the other also new battery in 2 months. not getting any module errors in inpa either (other than auc sensor), will have a tinker with ista tomorrow see if it can tell me anything.

[ptarditi]

Try unplugging the MPM, they were known to cause issues, also check your rear window, does it feel warm?

[bmwdirtracer]

I got ista+ setup and running and still learning it but whats the best way to check whats using power through the night with ista?

There should be codes for the electrical discharge. Follow through the test plan for those codes, and you'll find the item that's been keeping the car awake at night.

[reegz]

So I eventually got ISTA working and this is the most detail I could find about the drain source, not familiar with these modules, anyone know the likely candidates attached to these modules?

current monitoring.PNGkcan.PNG

[jclausen]

You need to do a draw test hooking a meter between the positive cable and battery post after the car has gone to sleep about 20 mins then see what the draw is if it's high pul one fuse at a time when the draw drops after piulling the fuse, you need to see what is on that circuit, reinstalling the fuse then disconnect one by one what ever is on that circuit

[reegz]

You need to do a draw test hooking a meter between the positive cable and battery post after the car has gone to sleep about 20 mins then see what the draw is if it's high pul one fuse at a time when the draw drops after piulling the fuse, you need to see what is on that circuit, reinstalling the fuse then disconnect one by one what ever is on that circuit

I did a draw test previously, after it had been asleep 40 mins, we got nothing, which confused me so I thought maybe the issue was intermittent but thinking back maybe I didnt have the multi meter low enough at milliamp level which is why I didnt get a reading when it was asleep but got 8 amps when awake.

[reegz]

SOLVED: did another test last night with the boot open, glove box open and doors open but latched closed to trick the car to think they were closed. tested voltage drop on every fuse in the boot, they all dropped to 0 or very small, tested fuses in glovebox and second last one there was a constant 4.5v running through and it didnt drop.

Turns out it was the fuse for the telephone which is great as no-one uses that anyway so I don't need to replace anything so I pull the fuse, previously the battery dropped from 12.7v to 12.38v in 42 hours, I note the current voltage and check back 12 hours later = no battery voltage change I thinks thats my culprit. I can start to regrow the hair I lost in this process now,, thanks for you help everyone.

[shadowpuck]

i'd guess the phone talks over the CAN network - it was probably keeping the network alive. Glad to hear you found it!

I need to learn more about ista and what it can tell you on these problems....

[reegz]

At the end of the day although ista can be pretty informative it didnt really pinpoint the problem this time. Glad I own a multi meter although I think I need a batter one mine might have dodgy leads.