Dead car battery and non-functioning Smart Key

I was driving to dinner last night...noticed msg on my display about low key battery. After dinner, drove straight home...same msg on display. Parked her in the garage.
An hour later, I noticed the Smart Keys were acting up. One key was completely dead. The other Smart Key was only able to Lock-Unlock-Pop Trunk by pressing buttons on the remote...it was not able lock or unlock by touching the driver door handle.

I drove to a convenience store at midnight and bought new CR2025 batteries for both remotes...installed and now, same thing. At 1 am, I call up MB Roadside Assistance, they says it's a dead car battery. I confirm this, my interior lights are dead now. I have a battery charger, so I decided to charge it up myself and hope for the best.
The car has been charging for 5+ hours at 2 amp mode...the battery is at 50%. I tried the Smart Keys again....same thing...with new batteries in the Smart Keys...one does not communicate at all with the car....the other was able to Lock-Unlock-Pop Trunk by pressing buttons on the remote...it was not able lock or unlock by touching the driver door handle.
Also car wont start....Keyless Go is not working. Pressing the start button usually brings up the display options, but this also does not appear on the front console.
Any ideas?
Last edited by PHML; Oct 24, 2011 at 02:15 PM.
I was driving to dinner last night...noticed msg on my display about low key battery. After dinner, drove straight home...same msg on display. Parked her in the garage.
An hour later, I noticed the Smart Keys were acting up. One key was completely dead. The other Smart Key was only able to Lock-Unlock-Pop Trunk by pressing buttons on the remote...it was not able lock or unlock by touching the driver door handle.

I drove to a convenience store at midnight and bought new CR2025 batteries for both remotes...installed and now, same thing. At 1 am, I call up MB Roadside Assistance, they says it's a dead car battery. I confirm this, my interior lights are dead now. I have a battery charger, so I decided to charge it up myself and hope for the best.
The car has been charging for 5+ hours at 2 amp mode...the battery is at 50%. I tried the Smart Keys again....same thing...with new batteries in the Smart Keys...one does not communicate at all with the car....the other was able to Lock-Unlock-Pop Trunk by pressing buttons on the remote...it was not able lock or unlock by touching the driver door handle.
Also car wont start....Keyless Go is not working. Pressing the start button usually brings up the display options, but this also does not appear on the front console.
Any ideas?
Last edited by ghstudio; Oct 24, 2011 at 02:39 PM.

funny because my change key battery warning or whatever
came on yesterday......
the batteries are those 1.5V round chip batteries I think......

Last time I had a 'marginally weak' battery on my C350; it caused all the electonic hiccups, long engine cranking to start, and eventually the car wouldn't start one morning in the garage and caused me missing a very important business appointment (not good.)
My dealer recharged and reconditioned the battery, tested it three times, and returned the car to me saying it was fine.
A month later, the battery went back to 'marginally weak' again, caused all the electronic hiccups again, and eventually the engine failed to start and caused me late to another business appointment (not good, again.)
I brought the car back to the dealer, they put a new battery in, and all was fine since (they should have done it the first time.)
I am biting my tougue to say this... but now whenever I purchase a new Mercedes, in every two years when I do the Service B, I just ask my dealer to install a new car battery at my cost. And now with my new E350 that has Keyless Go, I would also replace the car key batteries every year during Service A, as a precaution as well. I know, I know... but it is from my hard lesson learned.
Just want to share my experience.
With best regards,
Last edited by axhoaxho; Oct 24, 2011 at 04:48 PM.
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Wow...didn't know that...read the operations manual...too bad it didn't say anything about being 80+% before normal operations are returned. I suspect a visit to the dealer (tow) is imminent. Why one Smart Key partially works, and the other does NOT work...is beyond me at this point.

Last edited by ImInPA; Oct 24, 2011 at 05:57 PM.
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After a couple attempts to start the car with Keyless GO....no luck. No sound at all.
The tech ask me to remove the Keyless Go button and stick the Smartkey in the ignition...I did that and it started up without hesitation....wow!!
WTF?!?!? Keyless GO is a NO GO!!
Also, my remotes still have issues....before and after replacing both remotes with new CR2025 batteries.....1 still does not work, and the other partially works. I drove straight to my the MB dealership after the car started. I checked it at Servicing and told them everything that happened since Sunday night.....dead battery, charging at 2 amp since Sunday evening, both remotes not working properly even after battery swap, unable to start w/ Keyless GO, etc...
The MB service rep says he just did a quick look...he claims everything seemed fine. I asked for a new battery, and I dont want to be stuck somewhere. He claims the battery seems fine, but they will check it out.
Right now...im waiting for their call when its ready for pickup. I sure hope they find out WTF is wrong with my car....ARGHHH!!!!
Last edited by PHML; Oct 25, 2011 at 08:06 PM.

you just got your car no?
an experience like this could really ruin the love for the car....
but I hope that doesn't happen.....
good luck, hopefully this battery business will be the end of your troubles you know?

but did replacing the battery of the car fixed the keyless go key problem?
I'm experience same problem.
I'm sure hes not on here anymore but was wondering any other members experience this problem









A car battery is made to give 12 volts and enough cranking Amps to start the car. You think the U.S. made big V8 engines take less amps to start so the batteries made and sold here are not good for a German car?!?
After warranty get the battery (or brake components) from third party suppliers. They are as good and in most cases better parts than the OEM parts for much less cost.
Any high quality or luxury car dealer pricing is based on the fact that most of the people buying their cars don't know what a spark plug is. And they don't need to either...
Last edited by Arrie; Mar 12, 2014 at 06:27 PM.




