So just bought my 2010 e63 amg a month ago.. Has been absolutely great up until this. I got a message on the dash last night with a red battery. Nothing else. Didn't think much of it, figured I needed a new battery. Well today, going down the road, the NAV unit totally shut off. I turned the car off and back on, came right back to. No problems, no hesitations with starting. No dimming of lights or anything of that sort.

Now tonight, I put a volt meter on the main battery when the car was off and had been sitting. Around 12.3 I believe. Cranked the car, on startup it was 14.8. After a minute or so, it was 11.8 pulled in my driveway and now the car won't start... Any ideas?

 

Sounds like something with the alternator. You would need to get it started and then check with the voltmeter for a little bit. It should be reading over 13 volts when running.

 

Life would be so simple if todays cars were built like they were in the 40's--however that aint so and although you may not know it you have a very complicated energy management system on that car and with complicated you need excellent diagnostics to sort out the problems vs"Oh it's gotta be the battery" approach,because that gets expensive fast with no solution"--my suggestion is find someone who understands the cars systems!!

 

Command shuts off when voltage is low. If that happened when driving. Something is wrong with charging system. Likely battery is bad now too from draining it dead.

 

Posted this video in my other thread, here's how it's acting when driving

 

It may just be the battery only as it will read weird numbers when theres a bad cell and it's trying to charge it off the alternator. I'd just replace the battery and if the charging light is not on you should be all set. If it's the original battery, you need one anyhow, check the date on the battery and see if it's been replaced yet.

 

It was replaced two years ago. The car sat up at a dealer for a few months though, maybe that ran the battery down?

 

I don't know, watching my car all day today, I've never seen it go over to 14.8 volts, let alone stay there. Right after I start the car it will quickly jump to 50 amps for a few seconds but the voltage never gets that high. Watching you video, its not really pumping the amps either. When the amps go negative, you are pulling off the battery and the battery isn't getting pounded, I didn't see it go lower than 12.5 in the video. Mine goes as low as 12.4 when its pulling amps like from a stop or something. It certainly could be the battery, but it could be something with the voltage regulator on the alternator as well. I just think if it was the battery, you'd see a serious sag whenever the amps were negative on the display.

 

Put a tester on the battery, they have those at Autozone and those places

 

Maybe this?

#are61
novae500
MBWorld Fanatic!

Join Date: Jan 2009
Location: Northern VA
Posts: 3,067
Drives: W211
No luck got the car up and running and still have the red battery light. Front aux battery not charging, sitting at 12.6v while rear goes to 14.0...so probably the aux relay cable is bad. Taking it to get diagnosed at my indy shop Benz Elite.

 

How should I check the Aux battery?

 

Beats me. I got the cheap model with only one battery.

 

Another thing to try is fully charge your battery with a charger. Then try watching the voltage in the car. From what I can tell. Fully charged battery is going to read roughly 13 volts and 1 to 2 amps most of the time.

 

I did that, and now I'm back here. Fully charged it read around 12.7

Ok here's what just happened. Once the video uploads I'll post. The alternator wasn't charging to save my life for a few miles. Got to the point where the battery was at 9.7 or so. It got so bad the car stalled out in a turn for a brief moment, and when I got in the gas it fired back up, with 102Amps and 14.7v. I got cut off by someone calling me in the video, when the car came back to it was at that high amp

 

Seems like it could be bad voltage regulator. Search w212 bad voltage regulator on Google. Found a thread on replacing it on the w211. Should be similar.

 

You should have your battery and charging checked with proper equipment. Autozone, Advance Auto, O'Reilly Auto parts can test your battery and charging system and the testing is free. Without testing, it is guessing. And guessing with a Mercedes will most likely be a waste of time and money.

 

I had it tested and they claimed it was all in perfect working order. That's why I'm so confused and upset at this moment. Was tested with a midtronix system, apparently what MB uses

 

Did the charging system also get tested when the battery was tested? Are all belts tight and tension pulleys working correctly?

 

Yessir

 

Well at this point I've got nothing. I can tell you that the battery in my Denali started going dead for no apparent reason and it tested Ok twice. It then went dead while at the car wash with the lights on and engine off( this was in like 10 minutes. ) I just said screw it and bought a new AGM battery, and that solved the battery problem with my Denali. I think sometimes a battery can test good when it is not.

 

Absolutely. My Denali did the same exact thing, a/c started acting funny too.

Tomorrow, I'm going to put a multimeter on the Aux battery. I got under the dash and got it out where it can be tested. If that is a no go, I'm debating whether I should go for the voltage regulator or main battery.

Main battery seems suspect considering this. When I turn the car off, I'm reading 12.7 or so. After a mere 5-10 minutes, it drops to 11.8-12.2. So it seems like the main battery is draining down when the car is off, pretty rapidly actually. But the deal with the alternator throwing anywhere from -80A to 105A beats me. I feel as if either the voltage regulator has it thrown off, or the battery has a bad cell or something of that sort and is throwing everything off. OR the Aux battery is. Aux battery is 6 or 7 years old, never been replaced. Man this is a pain in the ***. I refuse to take it to a dealer though. I don't have the time, don't have the money to blow there, and would like to learn about some of the issues by fixing it myself

 

Well your battery shouldn't be dropping down like that, thats for sure. I did read something about the A/C relay sticking open or something and that turning the A/C off before shutting down the car could stop it from draining. I'm assuming that if one of the batteries is messed up it would cause the other to drain down, but I don't have a two battery system. Regardless of those, something is definately wrong with your charging system if the battery isn't charging for more than a few seconds which it definately wasn't in that video. That was downright unsafe, you are very lucky you didn't get stranded somewhere. As much as I love working on my cars and I'm known to be cheap, today's cars are getting more complicated to work on at home. I'm guessing you don't have any sort of extended warranty? That was the number 1 thing for me buying this car, I wouldn't buy it without a warranty. I did a quick search and unlike me, it does not appear you have any independent mercedes techs around your area. I'd honestly say best bet is just take it to the dealer although at this point, you likely need to tow it.

 

Talked to a Mercedes master mechanic of 40+ years, he believes voltage regulator, but still also says it could be other things being of what nature this problem is. I tested the Aux battery, it's great. 12.6 with car off, 14.1 with it running. I have a voltage regulator on the way and will have it installed Saturday since it's the cheapest thing I can begin with.

Here's a theory I had. Maybe I'm wrong

So the car doesn't start acting up unless it's at full operating temp and has been for a while. Maybe the brushes on the voltage regulator are worn out, and when they get hot they just don't make a good connection anymore?

 

Are you sure you got the correct one? Apparently it has to be a specific Voltage regulator

 

I ordered it direct from the dealer, so hopefully they knew. Ha