Anyone have any pictures of where to connect the trickle charger. I briefly glanced under the hood and didn’t see any obvious charging posts for the straight-six engine. Thanks.

 

https://www.mbusa.com/en/owners/manu...e-12-v-battery

 

So in reading the instructions, it says to hold the reset button for ten seconds to start with the charging times dependent on battery size.

Can I just leave it connected for a few days unattended? Also, leave the hood fully open I presume, and does it matter if I lock the car?

 

What instructions are those? The charger's instructions? Trickle chargers can be left connected for extended time and they maintain the battery charge. Key is to use one that supports the type of battery in the car. These days it's AGM or Lithium. Don't know from the top of my head what type of battery the W223 S500 has, but the W222 had a lithium battery. It's very important to select the correct battery type on the charger. Especially lithium batteries have a very different charging profile. They are not happy if they get charged to a 100% and kept there.

As for the hood, you should be able to lower it and rest it on the first position of the hood latch, so that there's enough of a gap for the wire. The alternative is to put the hood in the service position. That's with the hood open further than normal and the gas struts secured with a latch. There should be a latch you can push in on the driver side strut that allows the hood to open further until the strut snaps in securely and holds the hood open for long periods.

 

Yeah, the instructions for the charger says to hold the reset button for 10 seconds if the battery is lithium, which it is. I ended up just leaving the hood open.

Does the charger know to not charge these to max based on the lithium battery type assumimg i leave it pluggedin for days?

 

Confirm battery type. You should have two main batteries, a 12 volt and 48volt. The 48 volt is lithium and charged by the car and or thru the 12 volt. I have similar set up for 2023 e450 and trickle charging is only for the 12 volt thru the pos post on the passengers side of engine compartment. AGM Battery. What brand charger do you have? I have c tek. Works great.

 

By the way, the charger showed my battery at 50% when it started. I kept getting 12V battery low messages in the app and it has sat partially charged for a year now (i don’t drive much).

 

Your OEM battery should be AGM, not lithium if I'm not mistaken.

 

Hmm, well it’s too late for me as I did the lithium process. However, it seems to be charging just fine. While it’s not fully charged yet the app no longer shows partially charged.

Can anyone confirm the 12V battery type in the straight six engine?

 

Please be sure of your battery type. It should be 12 volt AGM. if a lithium charger fails to stop charging when the battery is full, fire can result.

 

Google isn’t much help as it says it can be AGM or Li. The instruction manual says the same thing: either or. So how the heck can I tell?

 

[QUOTE=Frenetic;9221005]Google isn’t much help as it says it can be AGM or Li. The instruction manual says the same thing: either or. So how the heck can I tell?

My 2022 is AGM

It is easy enough to see in the trunk unlike the GLE that has it under the driver seat (that one was the same AGM as well in mine). The 48V is Li Ion (I believe) but none of my 12V are

 

Does it matter if the hood is open or closed? Also, it’s been connected for 24 hours and the battery still isn’t fully charged but the charger isn’t giving me an error. Also, I noticed the state of charge will drop from 80 back to 50% from time-time-time. However, the app no longer says partially charged just charged.

 

Yes, you should leave the hood open.

You have not indicated what charger you are using other than you stated it is in Lithium charging mode.
I believe it has been determined that your W223 has an AGM battery, NOT a Lithium battery.
You need to use a charger that matches the type of battery you have if you want to charge properly and help the battery have a long healthy life.

 

On my wife’s 2023 SL55, I connected the trickle charger directly to the 12V battery in the trunk. I hook up the pigtail in the trunk then close the trunk lid onto the charger cord. The cord is not pinched, and slides in and out easily. Ive read that while charging the 12V battery with a tender, the 48v battery charges thru the 12v battery via the car.

We drive the car a couple times a month only, so it always stays on the trickle charger. We can drive it on the freeway for 30 miles and when we get home and it’s back on the trickle charger, it takes 2-3 days before it shows full. The dealership says the battery is good.so idk why it’s like that.

I’ve got 11 trickle chargers going at all times, connected to my Harley, boat, trailer battery, etc. They’ve been like that for 2-3 years.

 

I’m using the Mercedes charger. Here’s the instruction manual. https://www.manualslib.com/manual/19...Benz-1049.html

I’m using AGM and the manual states that the largest battery can take 26 hours. When I first connected it, it showed the battery at 50%. After a while it went up to 80%. What’s weird, though, is that after 12 hours, I happen to notice it drop back down to 50% then go back to 80%.

I’ve read other posts here that indicates it can take a long time to fully charge. The charger itself is supposed to give an error message if the battery can’t hold a charge and so far, I haven’t seen it.

 

Thanks. Yeah, I’m using the posts in the engine bay and i just noticed I cannot close the hood even if I wanted to because of the alligator clip.

 

Did your trickle charger come with another pigtail that has ring terminals on it so you can mount it permanently on the posts? I think mine did, but I had to put an extension on it so the plug end sticks out from under the trunk carpet and can plug it in easily. I’m also using the MB trickle charger.

I’ve also noticed that the charger body gets very hot when it’s charging compared to maintaining. I have it suspended from my cord reel coming off the ceiling garage. This way, air gets all around it.

 

No. It did come with a cigarette lighter extension. That’s it. I got this charger from the dealership.

 

Looks like you have the correct charger. Some of the MB chargers from CTEK are for only AGM and some are for both Lithium and AGM.
The charging program can be elaborate and can take days to complete. If you visit the CTEK website and read the literature, you will see the multiple chargers and various charging patterns they provide based upon the battery type and condition.

One additional note: The owner's manual from MB tells you where to connect the charging cables but it does not indicate an important step in the process of charging the battery... when to connect/disconnect the power to the charger.
The manual from CTEK does tell you this step but not in a clear concise process. It is very important to plug in the charger to the 120VAC wall outlet last after everything else is connected. Same in reverse for disconnecting the charger. First unplug the charger cord from the wall outlet and then disconnect the charging cables from the battery. This is an important step to make your battery and the charger live a happy life. (say that in your best Bob Ross voice)

 

I don’t think that you can trickle charge thru the cigarette lighter. It’s disconnected when the car is turned off. Mine is.

The MB trickle charger is just a rebranded Ctek charger. Matching pigtails are available on Amazon.

 

Hmm, thanks. I did not do that. I’ll be sure to follow those steps.

Here’s another question: if i interrupt the charging process because i have to drive, is it safe to plug it back in the same day until it’s fully charged? Or on multiple consecutive days…?

 

That's concerning, I would keep an eye on that if it really is VERY HOT. It should not be HOT. A little warm but nothing more.

I've never had one apart but I would bet the charger is potted internally so the air circulation is not much of a factor in thermal cooling. I might be wrong and the components are exposed internally which would then require mounting in a position the manufacturer has designed...on the rubber feet in a horizontal position. Hanging vertical could be causing the heat to rise and soak the components above the transformer. This could be a possible reason your unit is getting HOT.

 

Yes. You can connect the charger anytime (other than when your driving LOL). It is an intelligent device and will determine the state of your battery every time you connect and determine the best charging profile to use.
Don't be afraid to use it regularly. Your battery will love you for it.

 

Also, i noticed the charger gets really warm as well. At least initially, then it slightly cools off (but is still warm to the touch). Is that because of the different charging cycles or should i be concerned as well?