H4RJ

So my car started to alert me saying that my key had low battery. So I switched to my spare. A few months in, it's started to do the same. I don't understand how my previous BMW didn't require a battery change in 7 years but my two MB keys won't last 4 months each. I place my keys around 4 metres from my car overnight so I can't imagine it's being drained by the car. Also I only drive around 20 minutes a day. Anyone else had this issue? Could this be a fault or is it a common thing?

deonsand

mine only last 3 and half month,but i use very often

JT25

Just replaced my batteries for both fobs too - Month 10

thenew3

Do you have keyless go? If you do and you keep your keys close enough to the car (20 to 30 ft) it will constantly communicate with the car and drain the battery very quickly.

your BMW likely didn't have keyless go (or whatever BMW calls it) thus the battery lasted 7 years.

My previous BMW key battery lasted 8 years 175k miles. My current E350 key lasts about 2 to 3 months with the standard CR2025 battery, or more than 8 months with a slightly thicker CR2032 battery. I keep my key about 10 to 15 ft away from the car.

My spare key is on the other side of the house away from the car and it is still on original battery after nearly 3 years. I use the spare about once every 2 or 3 months.

JT25

Yep keyless go

I keep my keys in the house 1 floor above so it's not close enough

I'd say they have had the fobs in stock for some time or used some cheap battery supplier

thenew3

I don't know about cheap batteries, I've tried several different brands of name brand CR2025 batteries, they all die after about 2 to 3 months.

The "cheap" battery that came with my 2nd key fob that I keep on the other side of the house is still fine after nearly 3 years.

The last battery I put in my main fob is a "cheap" ebay battery that came from china and was $5 for 25 batteries. I bought the thicker CR2032 and so far it has been fine after 8 months.

PJ550CAB

Must be the keyless go. One key fob went out a few months ago after 8 months of ownership, swung by the dealer and they replaced for free.

jonandgwen

11 months for me. However I am in and out of my car 4-5 times a day for work.

Matts2015c300

Mine made it 13 months with keyless go. Just bought a ten pack of cr2025's on amazon for $5.70.... So at 1.40/year not a huge problem in my book.

Cmersu

I had to change both key fobs within 7 months. I have keyless start.

ScubaKing

One floor above is probably still too close. It was for my Audi A4. Drained both fobs. Even the one I wasn't using. You can check by pushing panic button from where you keep keys and see if it activates.

Ejbrock

Ejbrock

I have been replacing batteries every 12-14 months.Will take your advise and store them farther away.

Thanks for the tip.

Macmerc

You can turn off the keyless go communication on the key - double press of the lock button should do it. This will save the battery for your spare key. When you want use it, just press the unlock button, and it's all turned back on.

Ejbrock

Macmerc

I will follow your instructions.

Thank you

Hellbent

I wonder if this is the cause of so many "keyless go doesn't work intermittently" problems. Reach in to your pocket and double tap the lock button on the fob, now the next time you walk up to the car it pretends it doesn't know who you are and won't open the doors.


Fob battery @5 months. Guess I can park around block...

StanNH

Unlikely to be related to most of the problems reported. I spent time with three C300's and all had the intermittent fob problem. In my case, a software update finally fixed it.

realness101

Just buy multipack of batteries of amazon or something.. thats what I did.

Xtrema

So if spare is in range, one should tin foil wrap it so it won't drain on its own?

Hellbent

I found this on cars.com long term test drive for the c300:


"Our dealership's service consultant said something went corrupt in the module, so a technician flashed the control unit with the latest software and we were back in business. The update was covered by our warranty. A few thousand miles later and we're still in good shape with a functioning Keyless-Go system"


https://www.cars.com/articles/would-...1420682915840/

TheSaint

Can you get the new 3 button "facelift smart key without the panic button?

GerritKw

If you don't use the key fob for a long time, double click the lock button and the keyless feature is temporarily disabled.
Single click on one of the buttons and the keyless is enabled again.

fabbrisd1

I understand the frustration -tMercedes uses Panasonic (good brand) who moved their battery factory from Japan to Indonesia about 6 yrs ago.

Since that move to Indonesia - the Panasonic Indonesia battery has had sh*tty life - and there have been all sortof bullsh*t "stories" that have developed over recent years about why the Keyless Fob's go thru these "bad batteries" so often.

The problem goes away by switching to genuine Maxell CR2025 - new E-Class/S-Class fob's CR2032 different size - the genuine Maxell is sold ONLY in "hologram" package - believe it or not this button battery business is fill with counterfeit brands.

A 5-pack - and Maxell CR2025's have a 6 yr shelf life - is Amazon like $3 - on my side I have our dealership buy in 1,000 lots for like $.37 each and have tech's and sales replace ALL new and used MB key fob's with ONLY Maxell - and we eliminated this little nasty problem:

Mjollnir1983

Honestly if you can afford a Mercedes, u can afford to buy spare batteries.

p.s. My experience is about the same with keyless entry, average it lasts around 10 months.

RunwayOneSix

Didn't know we could turn off Keyless GO. Just did this to my spare key

cidtek

If the car doesn't have keyless Go does the key fob still need this turned off or are they custom to match the car build?