micosan

Is it normal for the car battery open circuit voltage (OCV) to be 12.3 volts after being parked and untouched for 48 hrs?
(Modify 2/11/14 - The car was not in sleep mode causing the 12.3 volt reading. So this was not really an OCV)

The OCV is 12.7V after the car has been driven for about 10 miles, the battery is a new Original Equipment from Manufacturer (OEM) dealer installed and the battery has been registered according to the dealer?s invoice. 12.3V represents a remaining battery charge of only 56% for a wet low maintenance battery according to SI B 61 11 09 and http://jgdarden.com/batteryfaq/index.htm . When I took the car in to service for this issue the service adviser (SA) reported battery is good and no draw detected. The car OCV after being parked and untouched for 2 weeks was still 12.3V.
(Modify 2/11/14 - Again the car was not in sleep mode and this was not a true OCV)

If 12.3 OCV is not normal what is a standard procedure for a Technician to do for finding the cause. Is an Energy Diagnostic a standard practice for low voltage complaint and does it require much time to run? I don?t believe an Energy Diagnostic was run.. SI B 61 13 05 has a statement ?The vehicle must have had a dead battery before Energy Diagnosis can be performed. Also, fault codes must not be deleted,? which sounds like Energy Diagnostic is only made when customer concern is a dead battery. I?m guessing in my case a concern of a low OCV doesn?t warrant an Energy Diagnostic.
(Modify 2/11/14 - Again I did not measure the OCV properly )

Here?s my calculation of energy used for the car to shutdown and sit untouched for 60 hours
Amps__Duration______ Amp/Hr_______Mode_______________Seq#
_______in Minutes
15.000__3___________0.75__________Reaching Idle state____1
1.500__5____________0.125_________Napping_________ ___ 2
10.000_2____________0.33333333____Consumer Shutdown__3
0.450__50___________0.375_________Almost asleep_______4
0.030__3600_________1.8___________Asleep__________ ___ 5
0.500__2____________1.6___________TCU_____________ __6

____________________4.98333333____Total
Information gathered from SI B61 08 00 and its attachments.

For an OEM battery of 110 A/Hr a 5 A/Hr draw is a drop of about 4.5% of the battery capacity. So the voltage should drop about 0.05V at the end of 60Hrs. At a draw rate of 0.030 A/Hr it would take about 60 days before the battery would drop to 50% capacity. This is assuming a new fully charged battery is in use.
(Modify 2/11/14 - the 60 days mention does not include internal resistance which would decrease the number of days available and additional damage to the battery would be caused by sulfation )

(Modify 2/11/14 - My OEM BMW battery was replaced on 9/30/2009 and again on 1/5/2012 by the dealer. Both had a dead cell. I'm sure I got caught in a bad batch from Exide)

Thanks for your input

Rudy

All of this is way above my pay grade but it's interesting to read. After a quick read of some of the bulletins you quoted, it's not clear to me if your OCV measurement of 12.3 volts (after the car has been parked) was taken while a surface charge was present. Did you follow the directions on how to remove the surface charge?

It's been a while since I've looked closely at any battery discharge troubleshooting service bulletins (and a couple of the ones mentioned I don't remember ever seeing) and since we seem to have plenty of members with the "increased battery discharge" issue and/or plenty of members who've been told they have an "unfavorable driving profile", I'm attaching some of the battery related service bulletins and attachments to this post so we can hopefully help people solve some of these problems. One thing that may be important to note -- it looks like BMW recommends that dealers use a "Midtronics" battery tester to better diagnose whether a battery is good or not. After reading a bit more about that particular tester, it seems as if it's very possible that a dealer that doesn't own one of these has a higher probability of mis-diagnosing the condition of the battery!

Unfortunately, some of these documents aren't very helpful for the common DIY guy but nevertheless, they may help with communicating with service advisors and technicians if you're getting the unfavorable driving profile line of BS...

Performing Energy Diagnosis:
SI B 61 13 05 Performing Energy Diagnosis.pdf

Closed-circuit Current Management:
SI B 61 08 00 Closed-circuit Current Measurement.pdf
Troubleshooting guides (attachments):
E6x up to 9/2005: B610800_Troubleshooting_E6x_up_to_9_2005.pdf
E6x from 9/2005: B610800_Troubleshooting_E6x_from_9_2005.pdf
Normal Closed Circuit Current Values: B610800_Normal_Closed_Circuit_Current_Values.pdf

Battery Charging and Testing Procedure:
SI B 61 11 09 Battery Charging and Testing Procedure.pdf

BMW Battery Tester:
SI B 04 25 02 BMW Battery Tester.pdf
Midtronics Conductive Battery Testing Q&A (attachment):
B042502Attachment.pdf

tooltec

I am not aware that BMW use a "wet" battery,i.e. a conventional lead-acid which can be topped-up with distilled water.
Sealed low maintenance lead acid batteries (valve regulated lead-acid) are standard fitment.The voltage characteristics for this type of battery are different to a conventional wet battery.
From memory,your figure of 12.3volts sounds about right so what is the basic problem here?
By the way,I would not call it open circuit voltage,it's the battery terminal voltage with standby (sleep) load.

tooltec

This should be good news for you!
After 16 hours garaged,my battery terminal voltage (car unlocked,smart key not inserted) was 12.28 volts.I do not have any battery issues.

Rudy

tooltec, it looks as if you didn't read all the documents posted above. They specifically mention the term open circuit voltage and, in addition, give specific instructions on how to measure it, etc.

Maybe I'm missing something (since I didn't go back and re-read all the docs posted) but your measurement of 12.28 volts may or may not be comparable to the number the OP mentioned...

tooltec

No,I didn't read them all,but one of the points I was making regarding "open circuit voltage" (OCV) still stands.If the battery is in the vehicle and it is not disconnected,you cannot make a true OCV,it is a voltage measurement with minimum load (assuming no faulty control units).However,looking at the documents,I now see that some tests can be carried out on the battery out of the vehicle,in this case a true OCV can be measured.
I have assumed that the OP measured 12.3 volts with the battery in the car,and that is what I did.If that is the case,the OP does not have an unusual measurement and that was the original question.

umermariner

Hello,
Pretty intense information I have a relevant somewhat high level question, and hope it would be a piece of cake for you guys .
My E60 battery voltage is 11.8 usually, and when charged fully, goes up to 12.2 volts. Based on my reading, its almost gone, however; it never gave me any issue (so far). The car is about 7-8 years old, and I dont know if it was changed or not.

Based on my reading, fully charged battery should be around 12.75 volts. Is it also true for our E60 battery?

Thanks.

BimmerFan52

Surface voltage and the car being awake does come in to play when measuring the battery.

OP - You mention that your measurements are taken OC (with at least one lead disconnected) so the state of the rest of the power system of the car should be irrelevant. You mention that the voltage is 12.7 OCV after charging, but don't mention if you leave the battery disconnected, or reconnect it to the car before disconnecting it again to measure 12.3OCV. I would assume you reconnected it while waiting the 48 hours.

As an example of measuring the battery while connected to the car, after an adequate charge, and 12 hours sitting idle to insure any surface charge has dissipated, my battery with the car completely asleep will read 12.65V (2 year old AGM).

If, after measuring, I then open and close a door the car will awaken, including fuel pump activation, and the voltage will drop to 12.35V and hold until the fuel pump goes off. Then the voltage will slowly rise for several minutes until reaching 12.55V. After the car completely goes to sleep again the voltage will return to 12.65V.

There are a number of different causes for accelerated parasitic current draw, depending upon the year and model of car. For early E60s the IBS can be damaged by moisture and repeatedly waken the ECM. In later models with comfort access, malfunctioning door handles can keep the system awake.

If you wish to accurately measure your car's parasitic drain, the attached, one of the better articles I have seen, outlines the issues involved and techniques used to protect your electronic equipment.

micosan

As Bimmerfan52 mentioned, part of my error was not waiting for the car to sleep. My car has a Park light indicator on the center gear indicator. This Park light turns off when the car is in sleep mode.

The voltage you mention seems extremely low. I wonder if your car was just waking when those measurements were made, which caused the voltage to drop. The battery voltage will drop significantly when the car wakes up.

The clock kept resetting when my battery started to fail but I did not notice any starting issue until it just quit. This seems to be a common symptom of a low voltage condition. Erratic error messages are another symptom.

To measure the battery voltage, I park the car, (don't open the hood ) open trunk and push trunk latch into close position and leave the car undisturbed for about 15 minutes. I peek through the window to verify the Park light indicator is off and then I measure the voltage. For my car, leaving the hood open will keep the body gateway awake.

I believe all 12 volt car batteries measure 12.65 volts when fully charged at 80F. I think the 12.75 volt was a theoretical or I read the AGM battery chart instead of the Wet Standard battery chart. You should probably reference the batteryfaq.org for battery state of charge at various temperatures. http://jgdarden.com/batteryfaq/SoC.xls

There are many ways to determine when a battery should be replaced and the most convenient might be to have an auto part store test the battery for you. But remember to test a battery an attempt must first be made to charge the battery fully. A good battery that is not fully charge may indicate to be bad by a battery tester. Also remember the alternator on a car is not a good charger. Its primary purpose is to keep a fully charged battery charged and to supply voltage to devices in the car, like the stereo, CIC, HVAC, ligths, etc...

I use two points of reference for replacing a car battery.

Firstly, I use the starting voltage. I replace the battery if the starting voltage dips below 9.1 volts at an outside temperature of about 30F during startup. Have someone start the car while you monitor the battery voltage. I “fully” charge the battery and then let the car sit overnight before running this test. However, it seems most people don’t have a charger available and most battery testing procedures state the battery must be charged prior to testing. 9 volt is the level at which the car computers may not work properly. If the computers don’t work properly then fuel, ignition and throttle may not work properly for startup.

Secondly, I would replace the battery if after “fully” charging the battery and resting overnight the voltage is below 12.4 volts at 80F. I would expect the first condition above would occur before this condition. But if a battery can’t maintain a state of charge above 60% then sulfation of the battery plates will quickly cause the voltage and amperage capacity of the battery to drop to a point of failure. That’s when you get the slow cranking revolution.

umermariner

I think one reason I might have had lower voltage would be not waiting till the car gets to sleep. Mine is manual, and I can just guess if its sleep or not (I can hear some dying noise), or give it 15 mins to make sure its sleep.

However, still, my voltage is towards the lower end, and that would be fine, if a lot of other people including myself didnt see the same low voltage on new batteries.

I just bought a pulse charger, hooked it up yesterday. Even though the battery was fully charged a couple of days ago, and didnt show any issues, it said the battery is 25% charge. Will check today if any progress .

My clock etc also got reset during charging. Not sure why though.

Thanks.