New style Key fob (rounded)
 

My key fob battery didn't work on one remote - or so I was told by service, on my 450 mile new 2018 GLE. Possibly it is not the battery and could be the key fob or something else. Surprising that they would supply a new car with a "stale" battery.

Anyways, while researching how to replace the battery (I probably will have the dealer do it under warranty, but doesn't look too difficult to do), I noticed that there is a new design "rounded-style" key fob that is currently supplied with some of the 2018 models. It seems to have a much easier battery replacement mechanism, but I haven't seen one in person, so I can't say if I like the style any better than the one I have. I'm curious. Does anyone know which models specifically this key fob should come with and should this be supplied for a 2018 GLE? Has anyone seen the new style key fob and what do you think of it?

You will have to buy a 2020 model year GLE to get the new "rounded" key fob.

1. if one-fob is going "stale" - best to replace batteries on both fob's

2. Although "factory" MB fob batteries - which are Panasonic CR2025 batteries - can be troublesome/"old" - the genuine Panasonic brand CR2025 replacements from legitimate source have been sound - like this $5 for 10 from Amazon:


3, These type of CR2025 batteries are one of the most brand/counterfeited items in the world it "used to be" Maxell CR2025 as last Made in Japan were the best replacements - but now 90%+ of those here in the US now are cheezy/poor China knockoff's.
The "MB brand package" batteries are in fact Panasonic 2025 repackaged into MB brand skin packs - but again the genuine Panasonic brand CR2025's do perform/last bettter - our dealership buy's 1000 at a time - since I have tech's and sales replace ALL new and pre-owned FOB batteries before customer delivery

This is true. However, I keep my second key fob deactivated so as not to use its battery. To do this, just quickly double click the lock button. You'll see the LED flash twice. Now, the key fob is completely turned off. It's no longer communicating with your car. I also do this with the fob I'm carrying, whenever I'm in an area where my key is likely to be cloned. E.g. malls, airports, etc.

Great idea to replace both at once.I mean, the car only has been driven 450 miles and is under warranty. I also like GL43 _Sube's idea about turning off the key when storing it as a spare.

An interesting side-note is that on the fob that "may" need a battery, when I click it, the red light does go on when away from the car. Now, I'm wondering if this will happen when I put it near the car and it won't work. I haven't seen this yet. I guess what I'm also wondering is how to determine if there are one of 2 other possibilities occurring - worth checking at dealer - can they easily check this?
1. Key fob itself has a bad transmitter and not a bad battery
2, Car receiver is bad and I haven't seen this issue yet with other key fob

You may want to invest in a good battery tester. It comes in handy for this and multiple other applications. This is the one I have. If the battery is good, I'd be 99% convinced it's the key fob over the car receiver. I even test brand new batteries, just to be sure they have a full charge. Lithium batteries have a shelf life of 10-12 years, so it's not likely they'll lose a significant charge sitting on the self. However, they could be defective or counterfeit if purchased somewhere other than the dealer. A battery tester will take all of the guess work out of the equation.

Good suggestion. I actually have a volt-meter, not a special "battery-tester" that I've used for testing batteries. I may try that.
Thanks!

I think something else is going on with this since the problem seems intermittent - sometimes works just fine with the key fob with possible bad battery, and sometimes it won't unlock or won't be recognized when inside the car. Usually when a battery is bad - it just won't work or gets progressively worse.

True. Also, it could be that the battery itself is fine, but the battery or contacts need cleaning. I've had that happen before with other electronics. Try using a regular pencil eraser to clean both sides of the battery and the contacts inside the key fob.

The car will tell you when you get in that the battery needs changing -- you have to press "OK" on the steering wheel for the message to go away.