zibby43

I have replaced my key fob battery 3 times in the last 3 months.

I'm using brand new Energizer CR2025 batteries.

I don't keep the key in the car and I only drive my C63 4-5 times a week, max.

I have Keyless Go.

m a x i m u s

That's weird. I haven't replaced mine yet. And in my old amg, the battery lasted 10 years. Are some other objects in your pocket or drawer or whatever maybe pushing the buttons somehow?

zibby43

Possibly but I doubt it. I would see results (e.g., doors locking and unlocking) if buttons were being pushed, correct?

I keep the key in the driver's side door pocket while I'm driving. I keep it right next to my wallet. I'm going to keep the key in either my pocket or the cup holder and see how long this next fresh CR2025 lasts.

Also, it has been between -5 and 25 degrees F here the last few months. Don't know if that has anything to do with it.

I'm about to buy some Energizer stock.

dchl21

no idea. but I keep mine is my pocket always and it lasts about 5 months daily used.

jas0ndotc0m

I'm using 2032 batteries I've bought on amazon. I'm pretty sure they are old and about to expire because they don't last very long on this TENS therapy (shocks your back numb, for people with back issues) I use, but it's about 2 dollars for 10 batteries. After they stop shooting electric shocks (to the point where I don't feel it) on my back, I toss it in a little box full of nearly dead used batteries I use for remotes (TV, car, etc) or things that don't need much voltage or mah. On TV remotes, these nearly dead batteries (AA/AAA) will last about a year or two. On my c63 key fob (2032), it has been 3 months and it's still going strong. On my other car, it lasted about a year. Think the batteries you are using are way past its expiration date.

Exhibit13

Same exact situation here, you didn't by chance order your batteries off amazon did you? Thinking I am going to try Duracell instead and see if that works better.

rentzington

I had the same issue and I moved to Panasonic or Duracell can't remember which and it's been 2 months on the same battery

From what I read trying to figure this out is that batteries made in Japan are higher quality and last longer...might be hooey though

******
Ok just checked its th reverse energizer works and Duracell kept dying

Diabolis

If you make sure you buy fresh batteries, they should last you about a year.

In humid conditions and climates, the button-type batteries drain just from sitting due to the relatively large surface area and the increased conductivity of the moist air. In some places near the sea / ocean (salt makes the moisture in the air even more conductive) they could be done if they've been sitting on the store shelves for a mere six months.

Mort

My dealer said they get better life from the MB batteries and recommend them to people with short battery life in the key fob. I tried some and he is right over the ones I was getting at The Source. But then it appears my keyless go had problems and the dealer replaced the main unit under warranty last spring and it has been good since. Still on the same batteries I bought the year before. There is no comparison to the way it worked before and must have been partially defective from the factory. More money but might be worth it to try the MB batteries.

HBC350

Just replaced the batt in my keyless go 2014 - 11 months old. Surprising since I get years out of batteries in all my other cars.

rentzington

I think the mb batteries are made in Japan, I found maxcell batteries are supposed to be great was planning to try those next once this one dies

Diabolis

Did all your other cars constantly communicate with the FOB the entire time the engine is running?

If you walk away from the C63 with the engine running and the FOB in your pocket, the "Key not present" message pops up on the dash in under five seconds. That means the car is communicating with the FOB the entire time, hence the higher drain on the battery. Most other cars (at least my Audis and BMWs) send and receive a code to/from the FOB just once at startup. You should still get about a year out of a fresh battery though.

(Sorry - just re-read yoru post, 11 months is normal. Same here on my 2013.)

Thrilla

I think the keyless go uses up power quite a bit. I haven't replaced the battery in my lexus key fob, but already replaced in the AMG.
On a side note. Sometimes the key fob is not recognized in my pocket when I touch the door and I have to press the unlock button. One time, my car was unlocked and I pressed the start button and it said key not detected. I pressed the lock button on the key, and it recognized the key.
I thought it was a battery issue so I replaced it and it still happens from time to time, but rarely. Anyone else experienced this issue?

jas0ndotc0m

hm, i have the keyless go too, i'm running strong w/ dead batteries

fsdafa78231

Hi,


Try CR2032 batteries.


Lee 2004 SL 55 AMG

Diabolis

They are thicker than the CR2025s by about 1mm. Won't fit in the new style FOB. Yes, the 2032 is a 220 mAh vs. the 160 mAh of the 2025, so if it fits by all means go ahead (same diameter and voltage so you won't kill anything).

Mort

Mine operated like that for a long time. Eventually the keyless go got up and went. MB replaced the main module under warranty about one month before the warranty expired and it has worked great since. About a week after the tech diagnosed the problem the keyless go started to work again but since they had a part ordered the dealer replaced it anyway and that was the correct decision as it would have failed again or continued to work erratically.

zibby43

The replacement batters I'm buying/using are brand-spanking new. But thank you for the response.

Weird. I'm glad I'm not the only one experiencing this.

I bought my batteries from a local pharmacy.

Interesting. Good info. Thanks Diabolis.

Thanks for the tip, Mort.

After I use up my last Energizer battery, I'm going to take the key to the dealer and have them replace the battery on their dime.

TampaBayC63

According to my dealer, the FOB communicates with the vehicle even when it's off, as long as it's located within a specific distance from the vehicle. For example, if you park in your garage and hang your keys right inside, this is most likely too close and will drain the battery quickly. Not sure if there's any validity to this but thought i'd share.

I got about a year out of my original battery and have since switched to the spare set.

Roswell

Ditto on buying the key battery from the dealership. I tried all kind of batteries & they all died quickly.

Decided to spring the extra few bucks & get the battery at the stealer, no problem since.

Valvestud

I leave my fob in the cupholder 24-7 for weeks at a time and have had no issues with battery life.


Regards,


Joe

JonMBZ

Do you have a spare and does it have this problem if not just have the dealer get you a new key under warranty. They will give you a free battery im sure. I give them out all the time. I usually give the speech about the key being to close to the vehicle as well and that's what I was about to tell you.

-Marlin-

I've had the same problems as mentioned in this thread with my keyless go. Sounds like there are some inherent flaws with it.

Great thing about these forums....being able to compare notes and all. Prior to this, I'd take a car in and the dealer would say "never seen that before...."

jcfay

I'll have to double check mine but I think they are dying kind of quick too. FYI on a related note I've always kept batteries in the freezer and I just read that is bunk (except for some rechargeable NiMH and Li batteries, IIRC). Time to thaw all my batteries...

Thrilla

Thanks mort. I'll have the dealer look into it.