Dear Whoover:

You may be correct:

1. The CTEK I recommended has a maximum output of .8 AMPS
2. The CTEK you recommended, the next step up in price has an output of 5 AMPS

Based on these specifications, I would buy the one you recommended.

Thanks for making me do my homework!

 

Costco has this 4 AMP charger/maintainer on sale for $39.99:

https://www.costco.com/.product.1005...0115_HotBuys-B

 

The fact that it doesn't have an AGM mode, only "Flooded/AGM" is a red flag. AGM batteries require different voltages, currents and cycle protocols. You also want one that has temperature compensation, because AGM cells are sensitive to overcharging when cold. These are some of the things that make the CTEK well worth a few more bucks.

 

Are our batteries AGM

 

Yes, all recent MBs use AGM. It's required for stop/start and, before that, required for Sensotronic brakes. Even though SBC wasn't used in all models, that's when MB started switching to AGM for almost all cars (around 2001).

 

I use the same Deltran Battery Tender on the motorcycle and car, just have a SAE pigtail installed for quick access to both.

If you do think you have a drain, a fuse buddy is nice to have. http://www.esitest.com/fuse_buddy.html

Came in handy on my corvette to find the driver seat pump was draining my battery.

 

Dear Whoover:

Out of Curiosity I went back to the Costco battery tender.

Here is what the description says:

• Selectable for AGM/Standard/GEL or Lithium (LiFePO4)* 12V only for Lithium
• Ideal for AGM, Flooded, Gel and Lithium batteries.

I have always used CTEK products as they are top of line.

But I also have confidence in Costco products.

As you can select AGM on the Costco charger/maintainer I think it is completely appropriate.

 

There are two selections: lithium and everything else. I would never use a charger that doesn't have separate modes for AGM and flooded (regular old lead-acid). This one uses the same setting for both ("AGM, Flooded and Gel"). That tells you it uses the same voltage and current settings for regular and AGM. Costco does sell a lot of good stuff, I agree, but this is not a charger I'd use on my car.

 

Thanks all, this thread has been very helpful, as I'm experiencing the same issues and had to have Mercedes roadside assistance out here to jump my car this morning. Can someone explain to me how the CTEK needs to be set up and how long it takes to work? It looks like it needs to be plugged in, and for quite some time. How often would I need to do that? I'm tempted to just buy the same portable starter that my tech used this morning, in case of emergencies, and otherwise drive the car on weekends to keep it charged. My weekdays are about 3mi a day, which is the problem. Thanks all!

EDIT: If it matters, this is for a 2019 C63S.

 

Setup is easy: open the hood, connect the red clamp to the copper post under the sliding cover and the black clamp to a nut that's attached to the frame. The CTEK should be in AGM/Automobile mode, which is the default so just plug it in.

Depending on how low the battery is, it can take up to 48 hours to reach "float," or 100% charge, but it will only take a few hours to get it above the voltage that triggers the alerts. In my experience, once you reach float you can put the CTEK away for months, even with little highway driving. I haven't gotten an alert in six months even though I only use the CTEK now if the car won't be driven for over a week. If I'm not going to be using the car for a couple of days, and if I remember, I'll connect it, but that's rare.

 

Sounds good, thanks. What seems odd to me is that I can drive the car for 4 hours, and then get the notice a week later after driving 3 miles a day for that week. I think a lot of this has to do with me leaving the car unlocked all night in the garage, which I won't do anymore after today.

 

Locking the car shuts down many of the circuits that are a drain on the battery. That you should do at once and every time you leave your car unattended!

 

Please don't let any of this get out to the rest of the world. The very idea that a new Mercedes needs to be regularly charged, and treated specially, to avoid a dead battery is just incredible!

 

I have the same problem with a year old E300 coupe. I'd like to hear from anyone who has found a solution. Battery chargers do not seem to make a difference. I have had the battery on charge overnight and still get the same message.

 

Virtually every car needs to be driven or have the battery charged regularly. The electrical drain from starting the car is significant and requires more than a couple of miles driving (especially with lights on and HVAC running) to recharge the battery to its previous level.

 

I've never noticed a difference with the car locked. Does anyone know of any electrical consumer that's turned off when the car is locked? Or an authoritative statement that locking the car makes a difference?

The biggest current draw comes from the radio communications module, which is always communicating with the server to report whether the car is locked or not, and when the battery goes from full to partial to critical charge levels. It's very quantum-mechanics: you can't observe the car's state without affecting that state.

 

Of course it needs to be driven or charged. But with other cars, driving it every month or so is sufficient. But many people here get chargers & trickle-chargers to hook up to their MB even when driven on a fairly regular basis!

 

Just picked up the CTEK battery charger and couldn’t be more happy. After reading thru this thread, it just made too much sense to not pick one up with my car sitting for days/weeks at a time.

 

Since I started this thread I thought I would provide an update. I continued to get the low battery warning in following weeks. I returned to the dealership and they did more testing of the main and accessory batteries in my AMGE43. One test showed an anomaly in one cell of the main battery. To appease me, the dealership replaced my main battery under warranty. I've had no problems since. I do now lock the car when it is in my garage. I also used the "Standby Mode" last month during a 3+ week vacation and my E43 started up just fine when I returned home. I still haven't bought a trickle charger. However, since I'm driving even less these days due to Covid19 I think the trickle charger might be a good idea to prevent battery issues down the line. Thanks for all of your helpful comments. Much appreciated.

 

Hi guys.. I think to add to this, I should mention that I've had stop/start not working for about 2 weeks at a time when it is not driven for few days. And the stop/start only started to work only after about 2 days of driving. (2hrs each day).
I did get a warning about the low battery at once stage.
After reading this thread, it makes sense to get trickle charger.

 

When the battery gets too low the car will automatically disable non-essential functions.

 

My dealer told me that Start/Stop will not work if battery needs charging, which I guess is logical.

 

I notice that the battery on my 2018 E-Class needs recharging when Start/Stop ceases functioning.
I'm therefore looking at these three CTEK Chargers.
- MXS 5.0
- CT5 Time to Go
- CT5 Start/Stop
Questions:
- Would they all do the job equally well? Advantages?
- Should I always the AGM Mode when using the charger?

 

Either of the first two are 5 amp models and should work well. The Time to Go bit seems like a gimmick. I use the MXS 5.0 and it works flawlessly. Yes, always use the AGM mode. It's the default on the MXS 5.0 so you just connect it and plug it in.

The Start/Stop is only 3.8 amp and I would avoid it.

 

Thanks. I'll go for the MXS 5.0