cetialpha5

Here's a key question I asked before, did you check the voltage with a meter?

Rehabguy

I have had my '14 ~5 yrs now. Gone through ~4-5 batteries. I barely drive the car and the key is kept two floor above the car. The only key fob I changed a battery in was from my old Sienna; once in almost 6 yrs, and that car was driven daily.

PeterUbers

Does anyone know if the keyfob uses up more energy (drains the battery more) if it's the daily use key fob vs being stored in foil (dormant) or in a distant location? In other words once the keyfob has engaged with the active vehicle is it sending more signals during the drive than the dormant keyfob?

Robert AMG

iTrader: (1)

yes if the key is close to the car it drains more the battery, and oem mercedes batteries are only the ones that works for long time, all other aftermarket batteries drain quickly, and if the oem batteries also did not work then your key is faulty.

1MavRick

In honor of this thread that I started years ago…this pic was taken, today. Hahahaha!!!

JimFE

@1MavRick Excellent! I know that screen well...

I took some time today to take some data.
- New batteries from Amazon (from www.licb-battery.com, according to the package) - tested three of them, they all came in at 3.26V
- The last one I took out of the remote after getting the screen above: 2.99V
- The one I replaced with (last week sometime) 3.11V
- The one in the other remote (that seems to be working longer ) 3.01V

So the new one is half way from new to 3.0V in about a week, but could be about ready to start misbehaving. I guess I will use these up (I got 10 of them...), keep taking data to see if it appears to be a battery issue, or a remote issue. It sure seems like these are crap batteries, though

knowbenz

Just FYI, there is a bulletin from MB regarding this that requires software update to Keyless Go module, it applies to a lot of models

thesaintusa

Have only replaced a battery in one of my FOBs, probably 3 years ago (DD in the winter). The 2nd FOB is still on the battery that came with the car (bought in 2017).

The back up key sits in a drawer by the door to the garage.
The daily driver key hangs on a key rack that is beside the door to the garage, so probably less than 10 feet from the car.

No idea why some people can go years, and others just a few months.

Mojo20032004

I am going on 3yrs with my batteries on both remotes. Still work fine. I live in a condo complex and I stay on the top floor and car is in the garage basement underground where even cell reception is hit/miss

cotmfk

I'm still on the same battery from when I bought the car 2+ years ago. Similar to Mojo in that the car and fob are far apart when not being driven.

The1stWright

It's funny you say this my key battery just died and I swear I replaced it three months ago.

brfatal

I get the warning messaged every 4-5 months on my primary FOB. In my wife's, for some reason, it's every other month. I last replaced her battery a bit over 6 months ago it's still working, just with the warning screen.

PeterUbers

I wonder what role RFI plays in killing the batteries when the keyfob is stored away from the car ... these key fobs are in the 433mhz range I think

JimFE

I assume the dealer can tell me if that had been performed on this car?

knowbenz

it might be in the VMI otherwise they’d have to hook up to the car and check the software version

cetialpha5

Do you take your car to the dealer for service? They change the batteries in the fob when you bring it in and they don't tell you or invoice you for them. I knew they changed mine when there was a different brand battery in them, I had Energizers in them before and I think it was Panasonic afterwards. Also seems to be a difference on whether you have keyless go or not. Both sets of mine are and they last 4-6 months before they drop below 3v and then I change them. I suppose I could probably go longer and see how long it takes before they fully die, but the warning message on the dash about a low battery is annoying so I just change them when that happens.

JimFE

Back again on this topic. Now the fob will not operate keyless remote, either with the battery I removed at 3.124V or the new one I installed at 3.268 volts. The buttons on the key fob still work (most of the time) and I can start the car with the key, but the keyless options are not working. The second (newer) fob still works fine, as it has for the 15 months I’ve had the car.

I’m guessing there are no “user serviceable parts” other than the battery, and no way to fix one of these things. But if someone else has an idea besides battery quality, I’m all ears. I’d be good with not dropping another several hundred $$ for a new key fob.

Thanks,

Jim

cetialpha5

The fobs do go bad so it sounds like you just have a bad fob and not an issue with EIS. How's the red light on the fob when you press it? Is it like the other ones? There's really no way to really fix the fobs. When you put it in the ignition, it doesn't really need a battery to work. If you're up for it, you could try some electrical contact cleaner. You should remove the batteries and make sure that the fob is completely dead by pressing the buttons and leaving the batteries out for a day. Then spray down the entire key fob and saturate it. Maybe some of the contacts are dirty. But if you have a loose connection, contact cleaner isn't going to fix it. You could also play with the connections on the battery terminals, they might be loose. Or try and reposition the batteries somehow, it does all sound like some kind of loose connection somewhere when you say it works sometimes and then sometimes not.

2013LBCoupe

I have to agre@Johnny Rad "
Here’s my experience. Old batteries and super cheap batteries online blow. Buyer beware."...

I have been using the cheap batteries (sunbeam) and I know that is the problem because when I used dealer service and they replace the battery every visit, I never had the signal to replace them. Recommend brand name like Duracell. Gonna go back once these run out.

cetialpha5

I believe the dealer uses Panasonic. I've tried them before but I tend to get higher voltages from Energizer. Usually there's a few people on eBay who seems to sell lots of them and you get a 10 pack so they're decent. But it can be a gamble. I've gotten some Energizers that were at 3.35 and some that were more like 3.25.

2013LBCoupe

Sounds good. It may even be good to just buy a single one as needed. I used to wonder why the dealer would replace them once per year on my car fob even though it never said it needed replacing but that was to prevent the eventual drain and then replacement.

cetialpha5

Well it's cheaper if you get at least 5-10 at a time as they still have to pay for shipping even if they offer free shipping which is typically just first class mail. I also have 4 keys, 2 of them take 2 batteries and the other two take 1 so I'm using 6 at a time. They're all keyless go and even though I don't use the other set, the batteries in the other set don't seem to last any longer. When they start getting weak, the keyless go part range tends to go down so I swap them out once they start to get weak.

2013LBCoupe

So you have had better experience with Energizers vs Panasonic? I am going to look for a pack on Amazon. They have to be better than the Sunbeam...the replace battery signal comes up just days after replacing. And I have had a really bad experience twice when they have gone dead even after replacing the battery --- the car seems to enter an anti-theft mode... I am going to respond to the earlier post where the fob does not seem to work anymore even after changing the battery.

2013LBCoupe

I have had some negative results with the fob after the battery goes dead and i replace the battery and follow the instructions on the dash. It eventually starts the car but only after an assortment of issues. Wondering if there is a fob reset of if the dealer can reprogram the fob before you give up on it. The response you got back was good advise...how did that workbout?

cetialpha5

It's a mixed bag. Amazon is known for having fakes and so is eBay. However on eBay you know something about the vendor whereas it's basically unknown who you're getting stuff from on Amazon. I only buy from vendors on eBay that have a lot of sales and have been on there a while figuring it's less likely to be fake or old batteries that are sitting around. Still it's still a mixed bag, somethings you get some with a voltage over 3.3 and other times just the 3.25. But I only do brand name ones, Sony, Panasonic, Energizer, Duracell, Maxell, etc. The only time I get high voltage ones are the Energizers. They're getting a little pricey now which is why I try Sony and the other brands once in a while. I don't wait for the fob battery to die, I change them out before they die.