Hi Folks.
Been having Battery Draining issues for the past year...
- took to dealer few times - no resolution

Been reading up on a few possible solutions here on the forum.
- Voltage Regulator
- BCM

Before I start ordering parts was hoping you all can help me out.

Im starting off with a new main Battery and have turned on the voltage display on the center console.

It shows a pretty consistent 12.5v -12.6v at all speeds. Shouldn't I be at around 13.6v - 13.8v? even after sitting overnight and after an initial start-up voltage sits at 12.6v.

Only when im in Reverse gear will it consistently be at around 13.6-13.8.

I have noticed that there are brief moments during a drive where i'll get 13.6.

I'm in a 2010 E550 4Matic.

Thanks in advanced

 

Can you give more details about the draining issues? Have you or the dealer checked with an amp meter in series?

BTW, how did you enable a voltage meter in the car?

 

Yes, what voltage display are you referring to?

 

I think he talks about voltage display in the engineering menu. It is there, I had it in the screen in my car once but can't remember exactly where it was.

 

Yes, your voltage should be around 13.5 V or higher when engine runs. Alternator or regulator has an issue here.

 

Arrie or anyone else with a w212 - can you turn on engineering during your next drive and report back on what you notice?

I was told by an indy, I called up that, this model has whats called "smart charging" which....

- has the alternator acts as a trickle charge 12.4-12.8v at cruising speeds.
- full charging (13.5-14.4v) occurs when battery is low, high draw is detected (seat heaters/air ride compressor), or during optimal times such as coasting down on a decline. ect...

This is a behavior which is intended to be more fuel efficient.

if anyone can plz report back on what they are seeing - it would be greatly appreciated...

To get into the voltage screen.
1. get in car and close all doors.
2. key to position 1.
3. press the answer button and hold then the ok button and hold. when both buttons are pressed and held - the screen should popup in about 5 seconds.
4. vehicle information is where the voltage read out is.

Thanks mates!!

 

Your Indy is correct. This smart charging has caused some angst among us and has been discussed before.

 

Thx Key08 - We have the same exact E550. mine is the Tanz Blue

Are you seeing the same voltage read outs as I am?

Seems like reverse is the only consistent state where voltage is above 12.6

 

Ok, here we go.


Returning from a trip and driving back home from the airport.


Entering to the engineering menu in my car works a bit differently comparing what you say but I got my battery voltage display in the screen. I have two voltages displayed. One is "Voltage to HU". The other Voltage via CAN.


Voltage via CAN reads 0.2 V lower than the HU voltage.


When I first started the car the HU voltage was at 13.6 V. When I set the gear on and started driving the HU voltage went down to 12.8 and stayed at this same value for the 12 miles I tested it.


I guess that smart charging does it at low voltage if the battery is full. My earlier comment about higher voltage was from time when my battery was old. I now have a battery about 6 months old.


This all starts to sound that the charging system in your car works fine. There just must be something that drains your battery when car is off or you have a bad battery.

 

Dude! thanks for doing that Arrie! greatly appreciated.

 

The voltages your Indy told you are consistent with what I have seen from measuring with a multimeter while the car was running at idle and under load. Didn't know you can view these in engineering mode. Would be happy to test it out if someone can tell me or point me in the direction of how to enter that mode.

 

here you go mate.

To get into the voltage screen.
1. get in car and close all doors.
2. key to position 1.
3. press the answer button and hold then the ok button and hold. when both buttons are pressed and held - the screen should popup in about 5 seconds.
4. vehicle information is where the voltage read out is.

 

This is the first explanation I've had about 'smart charging'. I monitored my battery voltage for a month and this is what I found:

- Started with fully charged battery 12.62V
- Just sitting overnight without using anything....never started, never opened doors, etc. .01 to .02 volts were drained.
- If I drove the car, including starting etc. it didn't seem to make a difference with the voltage.....unless AC was used. When the AC was used the voltage dropped .04 volts overnight. Several times I was measuring voltage or just in the garage when the evaporator fan cycled and I'm sure that's the reason for the .04v drop.
- The charge would drop to 50% (12.24V) and hover around there constantly no matter how much I was driving.
- My conclusion is "smart charging" is engineered to keep the battery at 50% charge level.
- I think the 'smart charging' theory is

 

I agree on the BS. My Honda maintains a very high SOC on the battery compared to my MB. No wonder batteries last longer in it.

In my car, I had to use the simultaneous press of call end button, # and 1 on the comand module to enter engineering mode. From there you go to 3.16 (select 3 first then scroll down to option 16) to see this (sorry for pic quality):


While the car was warming up, it read 13.4-6V but then after getting warm it read 12.5-6V during 99% of my driving for 1.5 hours. The only way I could get it to change was by flooring it from 0-80 on a highway on ramp, then it would read 14.3V.

From what I have read ~13.5-14.3V is normal expected output for an alternator. I guess running it at a lower level like 12.6V is 'smarter' if you're in the business of replacing batteries or promoting fuel economy. Although I doubt the minimal fuel savings are better for the environment or my wallet than more battery replacements.

 

Sorry, but I am new to this thread. I hear the "angst" but I have to believe that there is some variability to the cars' behavior, or else every one of the W212 owners would be on here complaining. That is what is happening in one of the BMW forums. Certain models of that brand have such an appetite for batteries that the manufacturer is telling dealers to replace the batteries with every oil change! (I think this is for one of the GT models.) Once these cars are out of warranty/prepaid service, the owners are looking at $750 oil changes every year for the life of the car.


Here at MBWorld, I see a number of owners having problems, but not every owner of specific models. What else is likely happening here?


I have an E400 4Matic sedan. What should I be expecting over the long haul?

 

These cars require a strong battery for all of the functions that are placed in these things. When the battery is weak, there are observable glitches in many of the powered up functions that lead to disgruntled owners, when it is only a weak battery. If the car is driven on short trips only it will not keep up with the proper battery charge and that is an issue that MB should explain to their customers. When these cars sit, there are several operations taking place(airmatic balance/leveling, A/C evap fan running); any of which will suck battery life.
Either drive it longer distances or use a trickle charger periodically to bring the battery back up to full charge.

 

You wouldn't even know your car battery was being maintained at 50% SOC unless you checked it. Apparently everyone's is though. The result is there are more, but not necessarily enough to shout 'fire', failures than normal. If all the right conditions line up....lights left on, door left open, radio on accessory, trunk open, long garaged time, or whatever.....a 50% SOC will fail before a 100% SOC. My wife's BMW uses the same charging algorithm and once after a week of being garaged it struggled to start, the 'check battery' light came on when it did, and the battery needed a charge.

 

I guess I'll find out over time, but it will be a while before my W212 is parked/garaged for more than a day or so.


. . . and hearing all this makes me more comfortable in my choice to take the MB extended bumper-to-bumper warranty. Hopefully that one will cover prematurely failing batteries.

 

Batteries are excluded from the extended warranty.

 

Correct, it's a consumable.

 

So I will have to just wait and see if my driving pattern causes issues. At least it is a battery, not a transmission. . .

 

Interesting, and yes, I have noticed this numbers.
And that was puzzling for me too, because they are not the standard numbers you would expect, especially when you have a new battery.
So, all this info is very good and useful and enlightening.
Also, I bought a new ctek 4.3 charger, so I can get the battery to 100% charge.

 

My car has the same symptoms... slightly different is when accelerate engine voltage down to 12.6~7V but during decelerating it increases up to 13~15V, then drop down around 12.7V ... strange, so I changed alternator & battery into new set. But the same symptom is continued.

I guess it would be a part of algorithm of charging system...(performance or battery protection or something? eg. IBS (Intelligent Battery Sensor)) somebody, who knows why, please tell me the reason...

 

Your assumption is correct. It only charges while cruising or accelerating if the battery drops below a certain voltage. It uses deceleration to charge. The purpose is to increase gas mileage.

 

Any dynamic voltage between [12.6v and 14.9v] is normal and well under control.

Most cars charging system work great, except for a troubled batch around MY'14...

During longer drives, if the alternator voltage swings below [12.3...12.1... 11.8, 11.x, ... ] it's a sign the charging system is deeply draining your main battery.

By the time you see 80Amp charge currents, it's a serious cause for concerns.
In that case manually switching headlights ON will supply 13.5 Volts and may keep you on the road safer with reduced chances of limp-modes.