I have owned my 2021 C63s cabriolet since May and only have around 1,300 miles. Obviously it spends a good amount of time in my garage. From the time I purchased the car I get emails from Mercedes Me stating the charge in my battery is critically low. When this happens I go to start my car and also get a warning on my dashboard stating the same thing.
I go for a ride for several minutes and all is well. Sometimes the interval between driving the car can be a week. Even with these warnings, the car always starts up. I am very impressed with this high tech monitoring system that Mercedes has but I have never had that problem with any other car I have owned which has mostly been Porsches for the last several years.
Should my battery be draining that much between drives? I'm a little surprised if I'm going to have to hook up a trickle charger. You would think that with the technology these cars have, there would be minimal battery discharge while not in use. Is this a common characteristic of this particular model?

 

I have the same scenario with my 2021 C63S -- a short drive isn't good enough, it needs to be 30 - 45 mins of driving and / or connect a trickle charger if you get the message. I've received the same message at least 4 times since ownership - especially the last two months as the winter weather has rolled in. I use a Battery Tender compatible with lead-acid, AGM, and gel batteries if I can't get out and drive it and that takes care of it. https://www.batterytender.com/battery-chargers

 

Thank you djprov431. Which model did you purchase?

 

Sent you a PM

 

*****Just get a trickle charger and hook up a quick connect kit so you never have to pop the hood, etc.. I have a NoCo Genius, cost like $50 on Amazon, and a quick connect kit, which was like $15. Leaving it on for weeks or whatever will not overcharge the battery, etc.. It's a smart charger that senses and shuts itself down or goes into maintenance mode, etc.. There are other brands out there too, I just happen to use this brand.

Driving the car for 30-45 minutes after it is critically low is just not enough time. If the car isn't driven often, put a trickle charger on it. An almost discharged battery might take 12-16hours to fully charge, depending on the charger used, etc.. These cars have a LOT of very sophisticated electronics on them and it is not the batteries fault, nor some kind of engineering failure, etc.. Batteries on these cars are not cheap at about $450 around here in my area as they are really nice quality batteries.

Also, don't keep the key in the car or very nearby it if it is not used regularly or it will discharge the battery in a couple of weeks or so if you have the Keyless Go option, or do not turn it off, etc.. The car will constantly be in wake up mode and using the battery reserves more as it is waiting to be started, or to unlock the doors, etc.. It's a very sophisticated system and several dozen systems wake up when it senses the key wake up handshake.

Good luck

 

So the battery in my C63s is Lithium?

 

I think "critically low" is a bit of an overstatement - it's still over 12V. Yes, a low amperage trickle charger may take 2 days, or you can do it faster with a high amp charger but who cares? The C63S battery is not over $400, unless you need it to say MB on it, nor is it a lithium battery. The car's 250a alternator will charge the battery much quicker than the trickle charger. The NOCO charger above would do just fine.

 

What is an AGM battery?

 

Removed. Better explanation can be found and further posts.

 

Mine is a 17 and a couple weeks ago after not driving it for a while I got a "don't turn the car off" message due to the battery. I keep my motorcycle on a tender and went out and got one for the car last week. Deltran Battery Tender with the quick connect lead on the battery.

 

Hace had this message many times the last 4 years when car in garage for month or so.

Never have a problem starting the car, I think is kind of a fake warning hahaha

Cheers!

 

Absorbent Glass Mat battery where the fluid is kept in place by a glass-based fiber/material. They typically exhibit much better life when experiencing numerous deep discharges. With all the electronics in cars, these days, a vast number of vehicles have migrated to this battery technology.

 

Unless that's changed in recent models, no. AFAIK all C63 S batteries are AGM technology. The GT series are lithium, however.

 

My car displayed the same message this week. Hooked up my Noco Genius 2 trickle charger overnight that I bought last year for one of my other cars and it indicated that the battery was low. I left it plugged in overnight and it was fine then next morning.

I live in a cold climate in my car sits for extended periods once the snow starts falling. I’m not surprised that sitting plus the single-digit temperatures have had an impact on the battery.

 

As discussed on previous threads, these cars don't completely shut down when parked. They stay online and keep certain telematics functions up so that you can remote start/lock/unlock from the app, check the status of the car on the app, and get alerts such as when the battery is low. This obviously drains the battery over time. Just like if you let your cellphone sit it will eventually run out of battery just from keeping the connection to the network. The critical battery warning is very conservative. It still has plenty of juice at that point to start the engine, but it will slowly start shutting down other unnecessary consumers like keyless go etc. to preserve enough battery charge to start the engine. AGM batteries also take longer to charge, so if the charge is low it may take a very long drive to get it charged again or hooking it up to a trickle charger will do the trick.

However, if your car sits parked for a very long time, you should take advantage of the standby mode to power everything down. It will also tell you how long you can leave the car parked before the battery runs out.

 

After recently having my C63S valeted I had a message on the dash to say "start engine see owners manual" with the battery symbol ... not totally unexpected I guess as the vehicle was being worked on for nearly 3 hours.
took it for a drive for an hour, message has not appeared since.
yesterday (3 days after valeting) we had a 6 hour round trip and at the end I checked the car in the Merc Me app and the battery is still showing as "critical" and yet no message on the dash... any ideas what could be causing this?

 

*****Battery could be going bad, or an alternator problem or both. I would put a charger on the battery and charge it fully and see if the charge holds. The Merc Me app sometimes does not update that quickly in my experience. Good luck, and hopefully it is just a discharged battery that will be fine with a good full charge overnight.

 

I would first make sure the app actually shows the latest status. On the home screen right below the image of your car it shows the mileage and next to it when it was last updated.

 

Went to pick up my car on April 28 and it had a "third brake light fault" which was caused by a short which it took them a over a week to find. Delivered the car two days ago, Tuesday, April 10. I charged it overnight to 80%. Yesterday we drove it 40 miles to an ASU graduation. Got in the car to return home to the message "12 V on board electrical system service required" alternating with another message that all braking functions were disabled. The brakes worked, but cruise control, braking safety, etc., did not. Crossed my fingers, drove it home with no problems, and took it into the local dealer (not the one I bought it from who is an hour away). This is possibly the very first EQS they have ever had in for service and so of course they are clueless.

In the EQS, the 12 V powers literally everything else in the car but the drive motor. As I understand it, in the EQS driving the car is supposed to recharge it, as is recharging the main battery. If you have the car turned on for a long period of time with no charging it can run down. Also, if you have the car turned on but not running, that will run it down. When Gilbert MB had the car to work on it and find the brake lite short, that may have been the case, both when they were searching for the fault, and when they were applying window tint and paint protection film. But that doesn’t explain why, when I recharged the car to 80% Tuesday night, and then drove it 40 miles down to Tempe, it didn’t recharge the battery.

This is my third EV. I bought a Tesla model S in 2013 and I've had two since then. I know in the Tesla, the high-voltage battery charges the 12V, so unless the 12V or the charging apparatus is faulty, the 12V shouldn’t discharge as long as the main HV battery has the power to keep it going, whether the car is “running” or not.BUT, it’s a cinch that the work they were doing on finding the short may have had the big battery disconnected long enough to discharge or even damage the 12V. ICE car automotive lead-acid batteries can be ruined if they’re discharged completely, and they can have their lives drastically shortened if they’re not totally ruined by a complete discharge. Isn't this the same? This may be as simple as just replacing the 12 V battery.

I've had two electrical faults and the car doesn't have 300 miles on it. I was planning to take a 3200 mile round trip toad trip in a few weeks. Now I have absolutely no confidence in this vehicle's reliability. Building EVs is really, really hard -Porsche t first couldn't keep there Tycoon on the road- massive recalls- and it was a mistake buying an early production model.

 

The EQS has known 12V issues it seems. As mentioned elsewhere, there's a German YouTuber called CarManiac. He has an EQS 580 and he had to take it in twice to fix 12V issues. Don't know what they actually fixed, but it seems the issue was eventually resolved for him. It's kind of funny that in the age of electric cars, the 12V system is the most problematic part. It is correct that many other EVs don't charge the 12V battery unless the car is on and/or driven. VW actually just released a major software update for the ID models, which among other things will now charge the 12V battery from the main battery if it gets low, even while the car is parked. Many of today's ICE don't use old school lead-acid batteries anymore. Most use AGM batteries and increasingly lithium-ion batteries. Not sure what type the 12V battery in the EQS is, but it's very likely a lithium battery as well.

https://www.interstatebatteries.com/...s-the-big-deal

 

My 2013 Tesla MS 85 had endless 12V battery issues.