E300-18

I recently needed to replace the SmartKey battery, and I didn't receive any advance notice that it was getting low. The first time I replaced it, I received a message on the dashboard that it needed to be replaced, while the SmartKey was still functioning. Is there anything I can do to ensure that I receive a message ahead of time? I had used the car a couple of days earlier, and the SmartKey was working fine.

On a possibly related note, I usually have the center display screen turned off. I rarely use the radio, and I find the screen distracting. I can't remember whether the "replace battery" message I received was on the dashboard display or the center display.

On another sort of related note, can I reasonably expect to get a message when the engine battery is starting to go bad?

JTK44

Not that I know of. I have received the exact same message when it was time to change the battery. You can wait a bit until you change the battery. You might have to put the smart key in the slot of the center console.

Dashboard

Yes

The G Man

I usually replace both fob batteries at every oil change, which is once a year.

JTK44

Not a bad idea!

I bought 12 batteries from Costco for $9.99. I also started to lock my Mercedes, which according to many posts on this forum, puts the Mercedes into "sleep" mode which saves the battery in the fob.

E300-18

Thank you for the information. I did put the SmartKey in the center console slot (for the first time), and that worked fine to start the car. When I arrived at my destination, I realized that I couldn't lock the car without using the physical key in the door. I keep procrastinating on learning how to pop off the cover on the lock, and I didn't have anything very valuable inside, so I just left it unlocked.

I initially thought there was something more seriously wrong, because the first thing I tried was using the other SmartKey, but it also didn't work. Apparently, its battery will drain over time, even if it stays in the house and is unused.

E300-18

Yes, I think I'll start doing that. It's such a cheap and easy maintenance item, and it's a hassle when the fob doesn't work.

The G Man

The fob battery is a CR2032 by the way.

JTK44

Less than a $1 a battery on Amazon:

see:

Bfgslkman

If you want a quick HowTo then there is a video on my YouTube channel