The "gages" in the 167 have the 12v battery monitored even if you have the 48V system. The purpose of gages is to monitor the critical information of the vehicle and the 48V battery is critical and the 12V battery is only for minor accessories. Why don't the gages monitor the 48V battery - it could provide information to prevent total failure of the battery and before the vehicle becomes non driveable? What up with that Mercedes?

 

I think both should be monitored along with moving the water temperature display from the left screen to the right screen....and show the oil pressure too. It's only software.

 

I wondered the same myself.

 

I asked the head mechanic at my dealership this very question about how do you know what the condition of the 48 volt battery was.
He said there was no way of knowing except for them to physically checking it with a special battery meter under the rear passenger floor.
Not really what I wanted to hear but that’s the situation.
I believe when the car is sitting idle the 48 volt battery is putting a charge back into the 12 volt AGM battery. I’ve really watched how this charge works with my multi meter. After driving the car and turning it off, the 12v battery shows 12.4 to 12.5 volts. An hour or so later I checked and the voltage shows 12.9 to 13.0 volts and is held like this.
I agree with all of you, wonder why Mercedes don’t want owners to know anything about this battery. Think they are nervous about people being hurt by the big voltage so no access.

Toban

 

I suspect that it’s not just a simple gauge to measure the State of Charge on a Lithium 48 volt battery. And if there was it would need to be converted to the 12 volt system to display. There should be some measure though since it’s the starter battery.
I tried a search and here’s what I found searching Lithium SOC...
The SOC of a battery, that is, its remaining capacity, can be determined using a discharge test under controlled conditions. The voltage method converts a reading of the battery voltage to the equivalent SOC value using the known discharge curve (voltage vs. SOC) of the battery.

 

You are right Ron, they do have a special guage. He told me what it was but I can’t remember.
As I mentioned, I may be wrong but I do believe the voltage from the 48 volt battery travels through the DC/DC voltage converter back to the 12 volt AGM battery even when the engine is off to keep it charged up. As I said why then would the voltage in the 12 volt battery be at 12.4V after I switch the engine off and a hour or so later the reading is12.9 V?
One can place a CTEK charger on the posts under the hood and places a charge in the 12V battery and the 48 Volt battery by the voltage converter the other way.

Toban

 

And I wonder why the voltage is ~14.7V sometimes and ~12.8 V at other times that don't make any sense at all.

 

AFAIK the times it is at 12.8 or less it is not charging and when it is 14.5 or more it is charging. The 12v is charged by a DC to DC converter from the 48V system at 14.8 volts which is normal AGM battery charging voltage.

 

I'm the newest member of the dead 48V battery club. The tow truck is on its way to take it 2 hours away to the dealer. I'm hopeful they'll work out a loaner. Mine was built Nov 2020 I believe.

 

Ouch and sorry for you. I just got my 53AMG and I hope I don't resemble that!!

 

That’s around the time they “might” have had a bad batch....heavy on the might. I don’t know if we are lucky that ours didn’t fail almost immediately like so many others! I guess the longer we waited the better chance that the new ones are fixed. Since this is a safety issue I’m surprised that there isn’t a recall.
A loaner is part of the deal but it wouldn’t hurt to make a request soon as you can...it might be at least a week. Its been 9 days since mine failed and no call yet. The battery was supposed to be in on day 7 but I haven’t checked. There were several other issues to fix on mine so the battery might be installed by now.

 

That was my next question, how long is it taking to get these batteries in. Also, I don't think I've seen it mentioned, but I hope this is a warranty repair. I think the warranty paperwork says batteries are not covered. The GM for Mercedes of Cary is supposed to be calling me to set up the loaner.

 

Batteries are covered both the Lithium 48 & AGM 12...I had the AGM replaced on my 2020 & now the Lithium on my 2021.
They aren’t going to be covered from normal use...like a tire, but are from premature failure...particularly these with a known defect.

 

I just got notice that my 48 volt battery arrived today, Tuesday the 25th. The dealer ordered the battery on the 13th so 12 days for delivery...not the 7 days noted when the order was accepted by M.

 

That's my understanding as well, but some times it doesn't make sense. When I first start the engine after not driving for a week, I'd expect the 12V battery to need some charging but the volts are ~12.7V. And when I've driven for three hours, the volts are pegged at ~14.7V when I'd expect the 12V battery to be fully charged.

 

Great, mine was built November 5th. I guess I've been lucky so far.

 

No loaner for me. The dealership said they're having such a hard time maintaining new vehicle supply that they've sold any loaners they get in. They've ordered my battery and I hope to find out tomorrow how long it'll take to get in.

 

No loaner so are they at least getting you a rental or give you a used one as loaner? I can't imagine you being without your car for what could be weeks for a warranty repair!

 

I purchased 7 year 100K mile extended warranty. I wonder if the 48V battery will be covered during this time frame?

 

Sorry to hear. Hopefully, it won't take as long as some of the other posts have suggested. My own experience was actually very good, all things considered. My 2021 E450 wagon was taken in on a flatbed on a Monday afternoon and I had it back with a new 48v on the following Friday. The battery actually arrived at my dealership on Wednesday but they also had to wait for a special thermal paste necessary to do the job.

 

I call BS. That’s no excuse...every dealer has the same issue and must allocate cars for loaners. I can see how they wouldn’t have a GLE but there are GLC’s and cars. My Dealer has no new Mercedes vehicles except for loaners and only 2 Porsche but they have about 4 Mercedes loaners. They also need loaners for service customers. I’m driving a new 2021 GLC with only 1,000 miles on it.
I would call the General Manager and ask for a loaner or rental car. Maybe someone else can confirm but I thought it was a condition of their Mercedes franchise.
Edit- with all the battery failures there could still be supply issues...my battery slipped a few days but at one time they were out 30 days.

 

It was the GM who called me to let me know the loaner status. I don't have a way to verify it, but it's definitely BS.

 

Sorry to let you know but the extended warranty does not cover the batteries at all. It's 4 years and that's it unfortunately. I checked on this when I was picking the car up and asked them. Unfortunately they said the extended warranty definitely doesn't cover batteries period.

I will definitely trade the car before the 4 years is up. The 48 Volt battery in Canada was quoted as $2800.00 plus 6 hours labour to put it in. You are close to $4500.00 including our taxes. Don't know how much the 12 Volt AGM battery is and it's not covered either. If you had to replace the 48 Volt battery, it will cost you this amount plus the $4650.00 for the warranty already paid.

The cost of extended warranty for 2 years was $4650.00 and an extra 1 year on power train only in Canada. This Is the 3 year plan.

Toban

 

Just got the "starter battery critical" email for first time in 2 years (4/19 build), and the car was just driven for over an hour the day before yesterday. Hope this is not the start of a failure! Is the Ctek 5.0 the best in chargers? I've never had to charge my Li-Ion batteries in my M4 or GLE, so just have an old Schumacher one and a small Battery Tender one.

 

Greg...that is for the 12 volt AGM not the Lithium 48. It says starter battery maybe because it is on the 350’s. When I got that last year they ended up replacing the 12 volt battery. Ironically I got it on my new car Friday after 7 days sitting. I’m picking it up this afternoon so will see what they have to say about that...7 days is nothing normally.