poraudi

For first time got in the car would not start as if no key....then 5 secs on display said take out stop start button and use key. This I did, everything working as normal. Popped stop start button back no -problems since. Now as you never put the key in ignition it does not charge up, so my question is when do you change battery in fob? could be that mine is getting flat.
Interesting if it happens you revert to using key in ignition.

msd3075

My car flashed up a message saying to Check Key Battery or something to that extent. It did it when my car was about 12 month (12K miles) old.

If you did not see that message, it might not be your key fob battery that's the issue. It might be an issue with the Keyless Go button itself.

If you want to change the key fob battery anyway, it's extremely easy to change. Remove the metal key portion of the key fob by pushing the sliding button at the top of the key. Then insert the metal key into the opposite side of the hole than where it normally goes (the part of the hole next to the sliding button. Push on the metal key, and the battery cover should pop off. Replace the battery with a new battery (mine is a CR2025 I bought at CVS). It'll take you longer to get the battery out of it's packaging than it will to replace the battery itself.

Also, if you do get the Change Key Battery message, it will not reset until you lock and unlock the car doors with the buttons on the key. If you use keyless entry, the message will keep coming up.

jrcart

These fobs go through batteries fast. They are in constant uses due to the car needing to remotely communicate with the fob all the time. I have not had a key fob battery last more than 9 months or so on any of my MB's/AMG's with keyless go. My wife's brand new GLE needed a fob battery after just a couple month's but I think that might have been because she always just tosses it into her purse and crap in her purse banging around depresses the fob buttons, at least that is my theory lol.

poraudi

many thanks I will order a battery, very helpful as to how to replace it!

ignomini

That's really interesting, and disappointing. My soon to be replaced S4's fob goes 2-3 years on a battery.

michael640D

Never had to change my BMW640d battery in the key less fob car is five years old

Sanch

Need to replace the batteries every 8- 10 months here...

ItalianJoe1

They do not recharge in these keys, so they don't last that long. On the bright side, they take all of 10 seconds to change. So it's a pretty minor hassle.

The dealer will change them anytime at no charge if you ask, mention it when you are in for service and you'll get a new key battery installed, I do them all the time.

Alex.currie44

Don't be doing that. Just go to a local hardware store that sells these types of batteries and change it. It is simple. Detact the metal key from the fob, insert the blade into the slot where the key is stored and the back pops off. Just remove the old one noting which way + goes, put in a new one and snap the back on and it is done.
I am a long time MB owner of 11 cars in the last 29 years and have a long relationship with these things and keyless go.
I get 4-6 months out of a battery. I am told - but have never tested the idea - that if you can seperate them by 10-12 ft when not in use they will last longer. Has something to do with communication between the car and key when in close proximatey. My key is always about 15 ft from the car when not in use.
I buy private label batteries 5 for $8.99 on a card and so far they as good as any name brand at a fraction of the cost.