L.I. Ryder

I think I'm having issues with my remotes. I have the keyless go option. I changed the batteries in both remotes and they both lasted 3-4 months each.
How long do your batteries last?

Sometimes the car says key not detected when I hit the button to start and then eventually starts. Also says it while I'm driving the car, the message will suddenly appear. I just changed the battery last week. The problem is Intermittent so it would be difficult for the dealer to recreate.
Anyone have this issue?

beshannon

I have changed one battery, not sure how long it was in the fob before I took delivery

KEY08

The batteries should last well over a year, so 3-4 months is not good. Do you keep your key in the same pocket as your cell phone?

DerekACS

Yes, I had a similar issue with my brand new 2015 E250, about 3 weeks after delivery. I kept getting "key not detected" messages and eventually replaced both key batteries - problem solved. The "key not detected" message seems to be a prelude to "replace key battery". In the first case, you can still lock and unlock the car, but if the battery is totally dead, then you have to pullout the 'keyless go' cover plate to insert the key to start the car.

As for battery life, based on my previous 2013 E350BT, I would say 6-12 months.
The current Smart Keys only have one battery, whereas previous versions had a pair. Maybe this change shortens the service life of the battery ?

I suspect that the Smart keys are produced well before the car is built or the installed batteries are not fresh ?

kash2014

yes mine only last that long too. I think it maybe because my keys are so close to the garage as another previous poster suggested, but I haven't bothered to put them somewhere else. I just bought a lot of batteries from Amazon.com for not much money compared to the store

YYZ-E55

6 months

Firenza

With Keyless Go, both keys' batteries last only 12 ~ 15 months.

BenzV12

Yup, 12-15 months . I was using Panasonic and replaced these with GP . Let's see if it will make any difference in battery life

thenew3

My first set lasted 6 months, second set lasted 4 months, 3rd set lasted 6 months, 4th set lasted 2 months, on my 5th set now and it's been 2 months. Got the replace key battery warning last week. I removed the battery in the key, re-inserted the battery and the warning went away and hasn't come back in a week.

I keep my key on a shelf next to the door to the garage so it's about 15 ft away from the car. That may be draining it faster than usual. My other key sits in a safe on the other side of the house. Out of curiosity I tried it today and it didn't get the replace battery warning. It has been sitting in that safe since I got the car 20+ months ago.

I bought a 20 pack of sony batteries off ebay for like $5 so it doesn't bother me to have to replace the battery every few months. It's a quick and simple process and I always get a couple weeks warning on the dash before the key actually stops working (replace key battery will pop up a few weeks before the battery is completely dead).

noka

Last BMW (which also had keyless go) were two years and still going strong. I see my supply of CR2032 computer motherboard batteries won't do, since the Benz uses CR2025. Glad I saw this thread. I'll be ordering some.

thenew3

Actually CR2032 will fit the MB key. difference between 2025 and 2032 is one is 2.5mm thick while the other is 3.2mm thick.

2032 also has more power. Both are 3V, but 2025 is about 150mah while 2032 is about 200 to 225mah so close to a 50% increase in power.

It takes a little bit of pressure to push a 2032 into the battery compartment of the key but it does work. (tested it myself).

I'm actually using 2032's now in my key since I work in IT, do a lot of computer work and thus buy and use a lot of 2032 batteries.

Alex.currie44

In my 2009 W211 Wagon the key fob batteries lasted a year but I did not have Keyless Go.
The 2011 W212 with Keyless Go goes through batteries about 4-5 months.
Pissed my dealer off during a service event when they changed the battery, charged $15 for it and charged 15 minutes labour.
Took it out, gave it back to them and told them to redo the bill.
I buy multiples at Walmart to cover 9-12 months.

L.I. Ryder

Thanks for the replies, i am suprised they dont last that long my audi and bmw keys just 1 of them lasted longer than both my merc keys.

I agree the batteries are cheap and i ordered alot of them i was just concerned that the fobs were about to fail and my warranty expires soon

Alex.currie44

Remember that you can lock the car with the mechanical key in the fob and the fob itself is the ignition key.

mikeyle

my key sits about 15-20 feet away from the car, and my first battery has lasted 17 months, with everyday driving but only about 12000 miles a year.

andre2p

I am having the same problem. In 6 months I have replaced the battery twice. The last one lasted maybe 4 weeks. I got the message Yesterday. My keys are about 20 feet from the car. Does that make a difference? My car has Keyless Go

thenew3

do you have keyless go? I've gone 4+ years in non keyless go cars but never more than 6 months in keyless go equipped cars.

thenew3

I think by keeping the key close to the car, something with the keyless go system is constantly communicating with the key thus draining the battery quicker. (just a theory).

Alex.currie44

I hang mine inside the house about 8 feet from the car and get 5-6 months out of a Duracell.

mbslk350

This is surprising. Our 2007 GL320 has keyless go and we're only on our second battery. We hang the key about 40 feet away from the car, if that matters. I also have a Ford Explorer with Ford's version of keyless-go. The key is also stored about 40 feet away from the car. I'm still on the original battery after 3 1/2 years. Maybe we're just lucky?

thenew3

40 ft is probably far enough so the system is not always communicating.

Dema

I noticed I get shorter battery life when buttons get accidently pressed by other keys in pocket. I several time noticed my trunk is open.
If you just commute and not so far then battery life is over 24 months.

flittlejr

I bought a CPO 2012 SL550 last year. Leave one in console (start & go) and is still going strong. Other one is in den (spare key drawer) same length of time. Just tested so working fine. I doubt if replacing batteries in key fob is part of CPO so maybe the fobs use less power?

El Cid

I have 2010 with Oct. 2009 build date without keyless go, just the "Smart Key." Both fobs were still working fine, but I replaced the battery in main one last week just to be safe. Will replace the other one eventually, but I only use it for dealership servicing.
I lock my car every time I get out, even when in my garage.
Real simple and batteries costs about $6.00 for a pair. Will keep the old ones in the trunk probably.

Dema

if you do not have keyless go feature, then you may never replace batteries. If battery goes completely down (Usually 5-6years), you will still able to start car, you lose only ability locking doors remotely. Not a big deal in my opinion.
Keyless go drains battery in 18 months in my experience. I was in situation when a battery has completely gone couple time. You need to pull mechanical key to unlock door and insert plastic part in ignition to start car. A bit inconvenient but again not big deal. Much worse situation if you won Lexus and your key battery has gone