2015 C300 with 24K miles. Got this message this morning. My commute to the office is only 5 minutes so I waited to shift to P after I got to the lot and let the car run.
Didn't notice any difference is running performance and it fired right up. But the message did return. Have an appointment this weekend. I'm guessing a new battery
is in my future.

 

mine did that and my battery died soon after...

Also 2 days ago my alternator died on me.. just 2 years in and only 15.000km... mechanic states its because I run air suspension and a lot of stereo system that puts a lot of strain on battery and alternator

 

Mine is bone stock. Hard to believe I would already need a new battery at 24K miles. Maybe the hot Florida sun beat it down. I'll find out tomorrow exactly what's going on.

 

So, where would you buy the new battery? Would you get it from the the dealer or Autozone?

 

15 with 24k. Warranty isn't it?

Charge counter needs to be reset with SDS anyway.

 

Should be covered under warranty. You never know with MB. I don't really feel like paying $500.00 for a battery

 

Why wouldn't you know. You are covered under warranty for a failed part. Use your warranty, don't be afraid of the dealership.

 

Is a battery covered under warranty? I figured it would fall under normal wear and tear

 

You figured wrong. Do yourself a favor and research how much stuff is covered. (Here's a hint, its almost all of it) Brakes and tires and alignment are covered 12/12k, the rest falls under factory warranty. Cosmetic stuff is not covered. Call and ask if you have a question, but make sure you get MB to handle that "$500" battery (Ours is $432)

 

"YOU FIGURED WRONG!!!!!"

No disrespect to you Robb, I just found that response kind of funny .

Also, cosmetics can be replaced under warranty if you have a good enough relationship with the dealer. I've had the pleasure (it's really not fun at all) of replacing several exterior chrome trim pieces on GL, ML, E, C, and S classes because of cosmetic issues from the customer "probably" not be washing their vehicle properly in the winter months. Now that we have had salt on our Canadian roads for the last four months, even my 205's exterior chrome trim has to be polished every two weeks or it starts to get spotted from the salt that never really washes off when I brush it at the car wash.

As far as the battery warning goes. If you leave accessories plugged onto you cigar lighter or 12v outlets alot, that can affect the battery life enough to set the battery warning even though these cars have "consumer shut off" once the car thinks there's a problem with the electrical system being drained. Aftermarket command starts and hardwired accessories like radar detectors and dash cameras, (if you have any) can also cause interesting issues or electrical gremlins on MB vehicles. There's also an electrical system event log in either the FSAM, rear SAM, or Battery sensor control unit that keeps a log of all electrical system activities for upto a year I think. But that, as far as I know, can only be accessed by a dealer. That log tracks any CAN-bus events, like if there's a CAN-bus network that won't go to sleep or keeps waking up due to a hardware fault with something in the vehicle. Or, if someone keeps accidentally pressing the lock or unlock buttons on the key fob while the car is sitting over night, if an interior light gets left on, or if a door gets left open.

Regardless, I would bring it to the dealer so they can figure out what the problem is and ultimately replace the battery under warranty before it leaves you stranded. Just be aware that there may be a minimum mileage that the car has to be driven every month or they might not warranty the battery a second time (not this time, but next time) if it's just low from the vehicle sitting for long periods of time. And I would get an AGM compatible battery maintainer of you do let it sit for a week or more at a time.

 

Picked the car up this morning. Replaced battery under warranty. My job recently relocated 2 minutes from my house which is great. Problem is I'm doing maybe 5 miles a week so the car is not getting much "run time"
and spends most of its time sitting in a garage. Hence the message "Leave engine running" Not sure if they were just blowing smoke, or if there is any truth to that.

 

I drive a short 3.3 km and 5-8 minutes to work monday to friday, BUT I also like to cruise around on the weekends. So that's probably why I haven't had a battery problem yet with my 205. If your car sits almost all weekend and because of your short commute, I would recommend getting a battery maintainer and plug it in every other week or so. Or you could just drive around for a bit every week end. Lots of electronics in our cars, means lots of amperage needed to keep the battery life maintained. The battery always drains slowly over time if you let the car sit for too long, so you have to either charge it while it's sitting or drive it more often. The battery may not be covered under warranty next time.... The easiest thing to do is drive it more often.

 

Try a nice walk. Maybe bike. But if you're starting the car and not letting it charge back up, its going to go flat. Simple as that. Add a trickle charger if need be.
Edit: Tuner beat me to it by a minute.
And no disrespect taken.

 

That warning happens often on these cars when the belt comes off. There's a bulletin about the alternator mountings being uneven, you basically loosen the alternator and re-torque it in the specified pattern and it seems to solve them. I've had cars with 2-3k miles sling a belt, no damage to anything, belt is perfectly fine just laying in the bottom of the engine bay. Drivers don't notice anything other than the message and loss of A/C because of the electric steering, but the cars can overheat if left like that.