[psuwtb]

Hi guys, looking for some help to narrow down an electrical/battery problem that I am having with my 2008 335xi (71k miles).

Symptoms:
Car will (typically) not start after leaving parked (unlocked in my garage) overnight. If the car starts, I will generally receive the 4x4 and ABS warning and/or increased battery discharge, loss of date/time, etc. on the display. If I use my portable battery pack the car will start without hesitation and no errors will be present (date/time loss still present).

Troubleshooting / Completed Actions:

• Verified that there is no parasitic draw once the car is asleep
• Verified that voltages are nearly identical at battery and front jump post
• Replaced Intelligent battery sensor (using new part # including 3 total pieces)
• Battery (currently 4 years old) tested good by two separate shops...both came back with no issues. Battery was registered/programmed when first installed
• Alternator - puts out 14+ volts when car is running
• Car starts fine when left on a trickle charger overnight
• The car almost always starts fine when we're out running errands (i.e. short trips, store to store), but more than half the time will not start when left overnight even though the voltage seems acceptable prior to "waking the car."

Example Scenario from this Morning:

Last night (@ Bedtime) - 12.52v

This morning (9AM) - 12.50v

Car was left unlocked; however, using my key fob (not comfort access), I hit the unlock button to "wake" the car. Without opening any doors, I measured the following voltages:

9:05AM - 7.98v
9:20AM - 10.36v
9:45AM - 11.49v
10:00AM - 11.73v
11:00AM - 12.42v

Any thoughts as to what could be causing this significant battery draw when waking the car (prior to starting)? Again, this only seems to happen after the car has been asleep (and likely left unlocked) for some period of time. I see a comparable draw when opening a car door after it has been asleep as well.

The only major difference when the car is home, is that it is left unlocked in my garage; however, the voltage levels appear to be at any acceptable range (~12.5v) until a car door is opened, or the unlock button is hit on the fob, at which time the voltage instantly drops 2-2.5v.

Thanks for your help!

[ctuna]

Is it real cold outside where I assume you leave the car when it
reads low? Have you tried getting a full charge on the battery
and observing it under the same condition?
Was the battery replaced with a battery of the same or greater
amp hour ratings?

When you unlock the car it should start drawing about .5 amps. Sleep mode is 20 ma when it exceeds 80 ma in sleep
mode it should alarm.
The car will eventually sleep even if you don't lock it.
if this is the actual value your battery may not be up to the task or it drawing more than that.

electical e90 pdf
http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU

Logical thing is to swap in another battery and see what happens cause it sure sounds like a battery problem.

[psuwtb]

Thanks for the quick response.

It's actually inside my garage where it's about 45F...so a little chilly but not freezing.

I just connected my trickle charger this evening and will test in the morning once there's a full charge to see if I experience the same voltage drop when a door is opened.

I bought the battery from Sam's ~4.5 years ago, and registered using Bavarian Technic...it's a Duracell 94R (pretty sure I had verified it was a similar sized replacement) and I haven't had any issues until the last 2-3 months.

New comparable battery - http://www.samsclub.com/sams/duracel...o:product:1:22

Completely agree on swapping the battery...had it out last week and couldn't believe when Sam's hooked it up and it had passed, so I took it to Advance Auto for their "free test" and had the same result. The symptoms to me, align with that of a bad battery but with all of the modules/electronics in the car, I want to be sure...

I'll let you know the results in the morning...

[ctuna]

Was the original a lead acid battery .(color white)
Is the one you replaced and AGM because you have
to reprogram the car for changes in battery type so
it has the right charging rate.
What are the specs on the 94rh7 is it AGM?

Amp/Hours = (Reserve Capacity / 2) plus 16

you are about 83.5 amp hours original battery's are
about 90 amp hours and are lead acid. Shouldn't make
a big difference.

[ptpending]

there can be problem with water pump, try to remove connector from it after you close car and leave for the night
also if your car have comfort access this can be comfort access door handle
check for the water in engine ecu compartment, clean water drains under hood near windscreen from tree leaves

[psuwtb]

Thanks again for some suggestions...here are the answers to your questions/comments:

• Original battery - was a white lead acid and was replaced by this Duracell 94R (Lead Acid); CA - 940; CCA - 765; Reserve Capacity - 135
• Regarding the water pump...interestingly enough, my water pump failed and was replaced with a new OEM by my indy mechanic this past October. I am pretty sure that these problems had existed prior to the water pump failure but they have gotten worse in the past month or so.
• Comfort access - I don't have this option, only a standard key fob

Some updates from today:

Left on trickle charger all night, this morning here are some numbers:

10:00AM - 13.21v
10:30AM (opened passenger door and measured one minute later) - 12.52v

10:35AM - 12.55v
10:45AM - 12.72v
12:00PM - 12.79v

14:00PM - 12.78v

14:05PM (opened passenger door and measured one minute later) - 12.28v
14:20PM - 12.71v

It appears that the "wake up" process brings my voltage down to a questionable starting level...after 15+ minutes the battery recovers and maintains a decent voltage. If I hadn't placed the battery on the trickle charger last night, I would suspect the voltage would be subpar 12.4v when a door was opened.

[TUFF E93]

Bad battery. Typical tests done at auto parts is with a cheap tester placing a max of 100 ca test. I have a digital tester that will test the actual cca at any given voltage. I have tested bad batteries that most auto parts say are still good.

[psuwtb]

Thanks for more confirmation that it's a bad battery! I know it's not worth fighting for the ~$75 that I would get back on the battery prorate, but it's just a PITA when their junk tests come back good. I'll plan to pick-up a new battery this week and see if that fixes my problems.

[TUFF E93]

You should invest in a digital tester. Harbor freight has some for about 70 bucks or so. They come in very handy. A battery can read 12.5v + and still have insufficient amperage. Voltage tests alone are pointless. Batteries over time will read higher internal resistance which can keep voltage up, but amperage decreases. Without having the car or battery in front of me, my best guess is battery is bad.

[ptpending]

have you registered battery replacement after you changed it before ?
if you didn't, car thought that it was weak and overcharged it and it's damaged now

[psuwtb]

Yes, the battery was registered using Bavarian Technic immediately after it was first installed (~4.5 year ago).

[patents]

Your battery is most likely bad. But another consideration is your driving habits. If you drive very short trips, your battery may not be charged enough. The car regulates the charging, and just because the car is running doesn't mean it's actively providing charging current to the battery.

(I also have a 2008 with 71k miles.)

[Wilt]

Originally Posted by psuwtb

Yes, the battery was registered using Bavarian Technic immediately after it was first installed (~4.5 year ago).

If you got 4.5 years on the present battery, that is about almost all one should expect to get...6 years on a battery in the past in automobiles (with only about 20% of the reliance on electronics in the E90) was all you could expect.

[psuwtb]

Just wanted to give you a guys an update...finally had a chance to pick-up a 100 Amp Battery Load Tester from Harbor Freight, and guess what...my fully charged battery showed up as bad on the tester!

Fully charged the battery again and took it to Sam's to for a pro-rated replacement. They tried it on their tester and the battery showed as not being charged even though it was fully charged (out of the car) 15 minutes earlier. After a little arguing and showing them my $18 Harbor Freight results, they prorated the replacement battery!

Long story short, the new battery is in the car, and I registered using the BT tool. Now we wait and see how it works!

Thanks again for all of the suggestions! Just proves that their $1000+ electronic tester is a piece of junk!

[STR8-6IX]

sounds like an alternator issue. has this issue been resolved?

[psuwtb]

New battery has been installed for ~1 week...*knock on wood* zero issues, voltage warnings, starting problems, etc. since installing!

Thanks again guys!