Was wondering if one had a Ctek battery charger and plugged it in at time when the car was in a garage over night or was sitting for a time if this would help with some of these battery issues?
Recently a poster commented he plugged his on all the time like over night etc and had no problems with his 450.
Just wondering. Any ideas on this or opinions?

Toban

 

The vast majority don't have battery problems. I certainly haven't in two years, even when not driving for over a week. If there is a battery issue likely charging is not going to be a solution.

 

Should help keep the 12 volt battery charged. Will have Zero impact on the 48 volt battery, the 450 isn’t a “plug in” hybrid. The 48 volt battery isn’t engaged until the start button is pressed.

 

I agree. I have two with e same propulsion system and no issues. One is 2.5 years old amd the other 6 months.

 

Thanks for the replies. We had learned over the last couple of months if you hook a charger up under the hood the charge goes to the 12v AGM battery and through a voltage converter to send charge to the 48 volt battery.
Guess that’s why I commented on this subject of charging? Any other comments are appreciated.

Toban

 

My understanding is that you are correct.
There definitely IS a 12v to 48v converter in the system, and I believe it's active with the ignition on or off. That's the guidance I received from my Dealership's top Tech, who said that you can charge the 48v battery from the 12v connections under the hood.
The schematics show two DC to DC converters, one 24 > 48, the other 48 > 24.

I plan on using my Battery Tender if I am gone for more than a couple of weeks.
The CTEK, Battery Tender, or other "maintainers" are more for maintaining a charge and keeping the battery healthy, than for charging a dead battery, though. They are designed to be left in place long term, not just hooked up for a quick charge.

 

I have a CTEK charger and love it. With COVID my vehicle sat for long periods of time and then I would only take a few very short trips. The app was starting to show Starter Battery Partially Charged regularly. I had a Battery Tender Jr. but that could not make a difference even after 48 hours. Used the CTEK once and problem solved after about 6 hours. You can leave it on as long as you want.

I should mention I have a 350 not a 450.

 

Thanks for the input but wanted to note the charging system is much different on the GLE 450 from the 350.

Toban

 

I have several battery chargers and recently used my best "smart charger" which changes power according to need and then switches to float mode. My GLS was sitting a lot and battery was never fully charged according the the app. I always saw a very high 14.7 - 14.9 volts on the MBUX screen gage so I decided to let the charger stay on until it would read as fully charged. It never did fully charge and gave an error code after 24 hours about a constant drain during charging. I assume from that, it is because the 12V - 48V converter acts like a draw during charging. My other "float" chargers fully charge the batteries as they are simple chargers. One observation from doing this is and watching the charging rate from the MBUX gage is that my readings go from 12.7 - 12.8 and 14.6 - 14.8 - nothing in between and it gives similar readings without the engine running. I am guessing the 48 volt battery charges the 12 volt battery even when the engine does not run. It also does not show any voltage drop when the ISG is providing boost. I find this odd because I don't think we are seeing battery voltage, only charging voltage for the 12 volt side. Why don't they show battery voltage for the main 48v battery?

 

Where do you find battery status in the app?

 

It is in the Service section. Only states Starter Battery is partially charged or fully charged that I have seen. When you go to the next "i" icon it states the Starter battery is a 12 volt battery whose main purpose is to supply electricity to an engine's starter which is not really the case. I am in Canada and we may have a different app now. Since the update we no longer see tire pressure as blank it just says "Tire pressure within normal...." because we don't get the tire pressure readings in Canada.

 

I've also seen the app say "Starter battery critical", but that was about a year ago with the older version of the app - and while some work was being done on the car.

 

Good explanation on the charger. Anything I’ve learned about this 12v/48 volt system has been from my own research and from this forum so thank you.
This is just my opinion but I think it’s important that owners with this system understands how it works. So, once again my research has told me when the car is running, the ISG generator is mounted along the driveline. It produces 48 volts which starts the car, runs the water pump since there are no belts. Also while the engine is running it sends the 48 volts through the voltage converter which I believe is attached to the 48 volt battery and converts it to 12 volts to charge the AGM battery. This battery is the Aux battery and runs all the electrical components in the car including headlights etc.
If you wanted to put a battery charger on the posts under the hood, this 12 volt charge goes first to the 12 volt AGM battery through it to the voltage converter which will convert this charge to 48 volts to charge this battery from the charger. It’s a two way converter.
The charger may be a long time getting to a float charge on the 48 volt battery but at least it’s getting a top up charge.
I don’t have my car yet so I am at a disadvantage. Can’t comment on what the gauges are saying or doing but it would be helpful to know so I know what I am looking at when my turn comes.
The description above is what I have learned about how this system works and charges. The owners manual on page 550 explain about battery charging also.
I’m from Canada also. My dealer has been really good.
another note, Mercedes has a new part number battery replacing the current 48 volt battery. Been told this is from a different supplier and should rectify any of those problems some owner have. Don’t know what the part number is. Was told when Mercedes issued a new part number means there is a change in components etc to produce this number. Dealer is putting one of these in my new car when it arrives near end of April.

Toban

 

I also see 12.7 - 12.8 and 14.6 - 14.9 on my GLE450. I'm trying to correlate to factors such as right after taking off my CTEK, after starting, while driving, etc. So far, there is no correlation that I can determine. When I think it should be in the 14 volt range, like after not driving for a week while not putting the CTEK on, it is in the 12V range. Sometimes after taking the CTEK off, it is in the 14V range. Sometimes not.

 

What battery are the readings of 12.6-12.8 and 14.5 -14.8v?
To me it sounds like the AGM battery. When fully charged with no surface charge, it should read 12.6-12.8v. AGM batteries seem to read a little higher than liquid acid batteries. On a charger, the voltage could be at 13.6 and higher and will slowly decrease to 12.6-8 once on float.
Once the engine is running the charge
should be in 14.5 range as there is a charge needed to replace what’s being used.

Toban

 

When the engine is running, sometimes the display shows around 12.8V and sometimes it shows around 14.8. It's either/or, nothing in between, and I can't determine any correlation as to why the voltage is what it is at any given time.

 

I guess 12.6v means the battery is fully charged and 14.5 v means the battery is being charged.

Toban

 

An automatic charger should only read ~14.5 during the absorb phase. 12.6 is a float voltage for a fully charged AGM

 

Correct.
Toban

 

Well, I took delivery of my 2021 GLE 450. Nice car with a really good ride etc. Part of the pre delivery, they were good enough to put in the new updated 48 volt battery for me. Forman confirmed to me the voltage converter was indeed a 2 way converter. So, if engine is running, the charge from the 48 volt battery flows through the voltage converter to charge the AGM 12 volt battery. When the engine is not running and you put a battery charger on the posts under the hood, then opposite happens. The voltage flows from the charger through the AGM battery through the voltage converter and supplies the 48 voltage/charge to that battery. He said this is why it can take some time to receive a float reading on the charger.
He also confirmed when you put a charger on the posts, since the charger is about 6-8 ft away from the battery, this could be cause for a bit reduced battery reading than if taken directly from the battery itself. He said they always check a battery directly from the battery posts when troubleshooting. But, he said for my case, the post reading would be close.

I bought a CTEK 5.0 charger. Just out of curiosity, I attached the alligator clips to the posts under the hood at about 3:00PM yesterday afternoon. I went out to the garage at 6:00AM this morning to see what it was doing. This charger has 8 stages of charges. It was on absorption #4 showing 14.8 volts. A few minutes later while I was there, the lights moved over to float on a green light. The voltage on my meter showed 13.6 volts. I think having the batteries on charge from time to time is a good idea.

I assume then BOTH batteries were charged up from my Forman's explanation. Good to know and thought I'd share this with all owners who were interested.

I have another question and will place it under a new post.

Toban

 

Does anyone know whether the Integrated Starter Generator (ISG) is brushed or brushless? Also, any info on the expected lifespan of the ISG (it is a major job to replace it)?

I've tried finding this info on this and other threads here to no avail. I've also tried emailing MB USA only to receive replies (more than one try) telling me to "contact a dealer in my area"...

TIA

 

It's brushless. See attached research paper if you really want to get into the weeds.

 

Thank you. Hopefully it means that it should not need to be replaced during the life of the vehicle, barring a defect of course.

 

Holy ! That’s impressive engineering, thanks for the paper. This significantly reduces the “wear and tear” of the Eco Stop/Start feature, which I like.

 

Can a CTEK be plugged into the 12 volt instead of attached to the battery with alligator clips?