eliteamg

Need some help figuring this out. Both main and auxillary batteries were replaced at 89k miles currently at 93k. Few day's ago car started weak but did crank and now just clicking and not cranking. I jumped it and drove for about an hour and will test the batteries on Monday but could this be a sign of a bad Alternator?
Thanks in advance.

Scott Gerhardt

The fact you drove it an hour after jumping it, makes me think it is not the alternator. If it was faulty, you probably would have run out of battery pretty quickly, but it could be an intermittent issue. Most auto parts stores can run a diagnostic on the battery and alternator. I would do that to rule in or out the charging system. If they rule it out, then you could have a slow battery drain somewhere. Maybe a sensor not shutting off.

PeterUbers

could also just be a bad main battery despite it being relatively new

Rehabguy

How long ago did you replace batteries? Time wise. Batteries usually last ~3 yrs. Some times you get lucky and they will last you 2Xs as long, but it's not a guarantee. Also, if you drive the car seldom and then driving short distances does not help. This is my case and that's why I plug in a battery tender after every short drive (Especially during the summer. You hear those cooling fans going long after you shut off the car) and when the cars sits for a week or so.... just to help the issue, This does not guarantee the battery will last forever either.

eliteamg

Thank you. It's been 2 days now and the car starts fine but I'm sure this will happen again. I think it's either a bad battery or sensor not shutting off.

Robert AMG

iTrader: (1)

check the starter.

Vrodman

could be this for sure. MB came to my house and replaced a battery under warranty. Battery was dead 2 weeks later.

Could also be alternator. Easy to test. Put a volt meter on your battery terminals without engine running. Should be around 12.8 volts roughly. Then start the engine and measure voltage. Should. be around 14 volts if alternator is working.

Good luck.

eliteamg

Due to labor day none of the shops were open around my area. I will check tomorrow but so far after jumping the battery few day's ago it's been starting up normal now. Thanks

fiveeleven

I had a similar problem about a year ago. Car would start the next day, but the battery would be dead if it sat for more than 24 hours. Battery and alternator were fine. There was obviously a parasitic draw. Took forever to figure it out, but the electronic ignition switch (EIS) module had gone bad. It just refused to shut off even after shutting off the engine and removing the key, so the car defaulted to thinking the key was in and never went to sleep and would constantly draw around 6 amps. None of the dash lights would turn on or give any external signs that the car was actively draining the battery.

eliteamg

Thanks for the update. I will check my batteries today and narrow down my search but EIS sounds interesting and will check that as well.

kponti

My E with less than 500miles on it almost died on multiple occasions cos I only drove it once a week for about 20-40 miles. Brand new everything couldn't hold a charge until I started riving everyday or using a trickle charger

eliteamg

It's been almost 2 months and it did it again today. Seems when I jump it lasts about 2 months. I think I need the dealer to run a scan and leaning towards the EIS module.

CaliBenzDriver

Are you familiar with the "engineering menu" on the dash?? Its a hidden way to display your main battery vitals while driving.

These cars feature Bosch smart charging that manages alternator dynamically from 12.6 to 14.9V... it is great!

The problem starts when buggy computers go nuts and drain the battery below 12v down into 11v territory while driving! At that point problems and various error messages can pile up due to CAN modules glitching...

Once computers are in limbo they don't work or sleep too well. The temporary solution is simple: disconnect both batteries for 10mn to reboot your car.

Between drives try to charge/float your main battery with a smart charger like CTEK or an OEM branded unit. Do this as often as practical to prevent charging currents reaching 80Amps while driving...

I gathered this knowledge in the non-AMG W212 forum. Hopefully this will prevent limp-modes and unnecessary battery swaps.

More power to y'all

eliteamg

Thanks for the info! Oddly, I am not getting any error messages on my dash. I can tell by the sound of the car starting it's about to do it again. After jumping the car starts normal for about a month.

eliteamg

Also considering it may be either Starter Solenoid or Starter Relay.

EckFe1

Just for reference, here you can see what the alternator voltage is doing on a short drive.

CaliBenzDriver

this looks pretty normal. ECU is busy recharging as quick as possible the main battery that needs it.
While this is not abnormal when ECU backs off higher voltage down to 13.x it then realize that more would be better and gets back to 14.9V.
The missing data is the battery current.
Is the battery being charged at 3Amps, 20A or 80A? That is an indication of how discharged it was.

Furthermore what happens after the 13.7 and the 12.6... 11.x? With what current 10, 20, 30 or 80A when ECU quits calibration cycle?

Typically you want to see battery charge currents staying low as high currents are an indication of a highly discharged battery.

eliteamg

Hi guys,
I wanted to update you regarding the starting issues. I brought my car to a local MB dealer and they did a full diagnosis and ultimately was the main battery in the engine bay. Previous owner had installed a WorldSource Battery which I never heard of and tried to do some research and funny as it seems I can't seem to find the price for these batteries. Out of curiosity I'm going to contact them tomorrow and find out more info. Meanwhile this simple problem wound up costing $785 for battery and diagnosis....lol
I really do hope this was the final verdict. Not sure if some of you may heard of this battery but I have never.

CaliBenzDriver

So glad to hear you're back on the road with a good battery this time.

I am curious, do you use ECO much at red lights?
I wonder if ECO usage is linked with reduced battery life .

juanmor40

I just cannot believe it. What did they do? Was an MB stealership? Or Bentley ?. Some here may want to know, so not to take our cars there

eliteamg

I know it's ridiculous charging this much for a diagnosis and replacing a battery but I did it for reassurance rather than constantly worrying about the car not starting. Only went there because I thought it was electrical issues.

juanmor40

If you keep it long enough, the battery will fail again. If you are a Sam's member, they can test the battery health with the Midtronics ( MB approved ) tester for free. Then buy it from your preferred supplier.

I think Battery plus store also uses Midtronics as standard equipment.

taphil

Group 49 or H8 AGM batteries are around $170-220 from your favorite auto parts store or bulk club store, mostly all made by Johnson Controls and custom labelled for each retailer. World Source seems to be the label for Advance Auto Parts. So the "genuine" MB battery wasn't too marked up in price, but the install labor and diagnostics was killer.

eliteamg

Thanks and I always keep ECO off as I do not like the engine constantly turning on and off especially in my area with a lot of traffic.