[gac90]

I recently bought a 2006 330xi, the previous owner had just replaced the battery (probably thought the issue was fixed with that), but my battery is leaking quite quickly (measuring 10V the in the morning after driving it the previous day)

We've checked the battery, tried switching to a different one my dad had lying around, and it did the same thing.

We also checked the alternator diodes and that isnt draining it either, neither are any of the glovebox fuses (at least not enough to matter)

Ive seen that there are some other fuse locations but couldnt find a good guide to them, are there some fuses somewhere else i should check?

Or does anyone know what else could be draining the battery?

Also the shift indicator light, trunk light, and glove box light are all turning off, we checked those.

(I think its draining 3.35 amps? Or maybe .335?? Something like that)

If i cant figure it out i'll just get a battery tender and master switch since im scared it wont start once winter really hits

EDIT: The problem ended up being the 6-cd changer in the trunk! It was draining the battery, we just pulled it out (just the piece that comes out to change out the cds) and no more issues! I did have to replace the battery due to the multiple times it died and sat frozen, and i got one with higher cranking amps and its been working great

[gbalthrop]

If a properly-charged, new battery is being drained to ~ 10V overnight, the MOST likely suspect is the Alternator (failed diodes NOT acting as "electrical checkvalves").
I KNOW you say you "checked" the diodes, but HOW exactly did you do that? I would suggest getting a "Clamp Meter" such as the MeterK MK06 (~$40 at Amazon), and FIRST seeing which of the THREE B+ Supply Cables is showing DC Current Draw. You don't have to "Open the circuit" with the clamp meter, and it is quite capable of reading the Current Draw you have which drains a charged battery to 10V overnight. That is Definitely MORE than .335 Amp draw, and the 3.35 Amp range sounds like proper ballpark.

Alternatively, you could simply disconnect the LARGE B+ Supply/Output Cable at the Alternator (AFTER disconnecting the (-) Battery Terminal), and then reconnecting the (-) terminal and seeing how much voltage the battery loses in ~ 4 hours. If virtually NONE, then the alternator is the Cause.

For those NOT aware of the three (3) different B+ Power Supply Cables from the Battery, they are:
1) Largest Red Cable from the (+) battery terminal down to the Right/ Outboard Transfer Point. That B+ Cable supplies power to the Jumpstart Terminal under the hood, and from there to the Starter & Alternator. If alternator diodes are issue, THAT cable will show 1+ Amp drain. Alternator diode drain will NOT prevent the car from going to sleep and Gear Indicator Light WILL go out after 15 to 30 minutes (Locked vs. Unlocked).
2) Medium Red Cable runs from Rear Power Distribution Panel on top of battery, INSIDE the vehicle (as opposed to beneath) to the Junction Box Fuse Box. If any circuit powered by a Fuse in that panel is drawing current, that Medium Cable will show significant DC Current (Amps).
3) Small Red Cable provides power to the VVT Relay & possibly OTHER components in the E-box under hood (White box at Right-firewall).

Please let us know what you find,
George

[e90yyc]

So you’ve put a multimeter in series with it and measured 335 mA? What George said above is true—it’s probably 3.35 A—but even 335 mA is way more than you should be reading.

It’s possible you have a module that is preventing the vehicle from going to sleep. You may not be able to determine that just by pulling fuses, but absolutely I would start there before moving onto anything more difficult.

If you haven’t already, connect your multimeter in series and lock the car. You should see a drop in current within 5-10 minutes. If you aren’t seeing this, then I’d bet your issue is with one of the modules.

As always, George has great advice so start with what he’s suggested

[E92William]

The fuse pulling method with an ammeter in series with the battery works flawlessly. We did it on a buddy's e38 750 so it should work well for the e90, we found it to be the rear cigarette lighter shorting out.

[gac90]

Originally Posted by E92William

The fuse pulling method with an ammeter in series with the battery works flawlessly. We did it on a buddy's e38 750 so it should work well for the e90, we found it to be the rear cigarette lighter shorting out.

We did all the fuses in the glovebox, i dont know where the other fuses are...

[gac90]

Originally Posted by e90yyc

So you've put a multimeter in series with it and measured 335 mA? What George said above is true—it's probably 3.35 A—but even 335 mA is way more than you should be reading.

It's possible you have a module that is preventing the vehicle from going to sleep. You may not be able to determine that just by pulling fuses, but absolutely I would start there before moving onto anything more difficult.

If you haven't already, connect your multimeter in series and lock the car. You should see a drop in current within 5-10 minutes. If you aren't seeing this, then I'd bet your issue is with one of the modules.

As always, George has great advice so start with what he's suggested

We did all the testing once the car fell asleep, left the door open long enough (although we didnt wait long enough for the shift indicator light to turn off) and we did see the drop

[e90yyc]

Hmm and it was still reading >3 amps?

[gac90]

Originally Posted by gbalthrop

If a properly-charged, new battery is being drained to ~ 10V overnight, the MOST likely suspect is the Alternator (failed diodes NOT acting as "electrical checkvalves").
I KNOW you say you "checked" the diodes, but HOW exactly did you do that? I would suggest getting a "Clamp Meter" such as the MeterK MK06 (~$40 at Amazon), and FIRST seeing which of the THREE B+ Supply Cables is showing DC Current Draw. You don't have to "Open the circuit" with the clamp meter, and it is quite capable of reading the Current Draw you have which drains a charged battery to 10V overnight. That is Definitely MORE than .335 Amp draw, and the 3.35 Amp range sounds like proper ballpark.

Alternatively, you could simply disconnect the LARGE B+ Supply/Output Cable at the Alternator (AFTER disconnecting the (-) Battery Terminal), and then reconnecting the (-) terminal and seeing how much voltage the battery loses in ~ 4 hours. If virtually NONE, then the alternator is the Cause.

For those NOT aware of the three (3) different B+ Power Supply Cables from the Battery, they are:
1) Largest Red Cable from the (+) battery terminal down to the Right/ Outboard Transfer Point. That B+ Cable supplies power to the Jumpstart Terminal under the hood, and from there to the Starter & Alternator. If alternator diodes are issue, THAT cable will show 1+ Amp drain. Alternator diode drain will NOT prevent the car from going to sleep and Gear Indicator Light WILL go out after 15 to 30 minutes (Locked vs. Unlocked).
2) Medium Red Cable runs from Rear Power Distribution Panel on top of battery, INSIDE the vehicle (as opposed to beneath) to the Junction Box Fuse Box. If any circuit powered by a Fuse in that panel is drawing current, that Medium Cable will show significant DC Current (Amps).
3) Small Red Cable provides power to the VVT Relay & possibly OTHER components in the E-box under hood (White box at Right-firewall).

Please let us know what you find,
George

We followed this video

(i have a relative who is a mechanic helping) and we also tried disconnecting the alternator while checking the draw on the battery and there was no change

[JuniorB]

Your IBS sensor is ng, replace the sensor before an alternator. An alternator can only discharge a battery if it’s running, or corrosion. A parasitic drawl wiillmalos drain a battery, but try the IBS sensor first.

[Kennybruv]

My 2006 325i has a weird battery drain problem. The battery will be fully charged but will be too weak to start my car and it will just completely drain if I try starting it just once. If I jump the car it will fire right up but if I try it without my booster pack my battery goes flat.

[gbalthrop]

Originally Posted by Kennybruv

My 2006 325i has a weird battery drain problem. The battery will be fully charged but will be too weak to start my car and it will just completely drain if I try starting it just once. If I jump the car it will fire right up but if I try it without my booster pack my battery goes flat.

If I understand your description correctly: You are measuring Voltage of the battery (either at the Jumpstart Terminals OR at the Battery Posts in boot) BEFORE cranking the Starter, and the reading is ~ 12.5V or at LEAST > 12.0V
Then you press START Button with foot on Brake/Clutch, and you just get click/clicking with NO Starter Crank. Measure Voltage again, and NOW voltage reading is in 10.0V - 10.5V range.

IF that is what you are seeing (takes specific Voltage readings with Multimeter to confirm), your battery has "a bad cell" or internal failure, causing it to FAIL the "Load Test" the Starter puts on your Battery at each start. You can charge it up to > 12.0V, and it may even light the interior lights when you open the door, but crank the Starter, and you're back in 10.x Volt range.

Since I can charge a sulfated battery that won't hold a charge for more than ~ 12 hours, most every battery I've ever replaced (after 7 to 10 years), has failed that way. It's NOT due to "Battery Drain" in the sense of Parasitic Draw by an electrical consumer. It's due to Load Test Failure: Inability to provide Cranking Amps under starter load = battery failure. NEW Battery required.

If what I described is NOT what you are experiencing, please provide CORRECT DETAILS.
George

[Kennybruv]

So your almost spot on, the only difference is I will measure 12.5v on my battery BEFORE I put my negative cable on (so it is disconnected). Soon as I put my cable on it will drop to 10v-8v. I have tried pulling fuses, starter, alternator to make sure nothing was actually pulling power from it but no luck. It does seem like it is just my battery but I did put in a battery I had lying around and had the same result, granted I’m not 100% sure if the battery is good or not.

Sorry I should have just quoted your reply but the app is a little weird 😹

[jv7890]

hi, I have 2006 BMW 325xi Sedan I'm having problems with my voltage too I changed voltage regulator, battery, check fuses and ibs Aswell grounds too but still battery drains overnight now I'm at 10v with jumper cables then after took off goes down to 9.9v till cluster and or car shuts off. Thanks for any insight into this problem!