But charging the 12V feeds voltage through upconverting to the 48V as well, correct? So it's important to have a Li-Ion compatible charger?

 

Yes, but my guess is that you have a bad 12 volt. On mine the Dealer was required to charge it overnight and then run a test before replacing it. Your battery should not run down overnight unless something like the lights were left on...? It might be quicker to take a 30 minute drive to see if that charges it back up.

 

That's a good question. I don't think the Battery Maintainer (Battery Tenders in my case) knows what's on the other side of the onboard 12->48v converter. Wouldn't the converter just be seen as a Draw?
Isn't the 12v battery a VLRA, using AGM algorithms? If so, the 12->48 converter would work at a 13.2v maintenance or float charge, I would think.

 

I agree, got in a hurry...I think you need an AGM compatible charger not a Lithium. As I recall that's what the Mercedes shop Foremen told me last year.

 

My service guy is fairly certain the extended warranty will cover the 48v battery. I'm going to get it in writing though.

 

Duece40s

My dealer is in Canada. I thought the extended warranty was the same in North America. Maybe it is not but I know the GM checked it for me. He came back and said they checked it and the batteries were definitely not covered after 4 years.

Toban

 

Just for a matter of interest, I bought a 5.0 CTEK charger. I've had my car for under a month. Out of curiosity, I put the charger on this morning. I had it set on the car and AGM mode.

I started to check it from time to time. It took 4 hours for it to go from Bulk charge to Float through the 7 steps. I think this charge is also going to the 48 volt battery by the voltage converter which explains why it took so long.

Disconnected the charger. Later in the day, I checked the charge on the posts under the hood and it read 13.03 volts.

I started the car up and the voltage on the screen under "info" and engine showed 14.7 Volts when it started and went down to 13.5 volts then to 12.8 volts and stayed there. This tells me the 12 volt battery was charged right up and no charge was needed from the 48 volt battery from the generator. Having said that, I wonder at what voltage the 12 volt battery goes down to before it starts taking a charge to build it up again? HUM!

Toban

 

That makes sense, but mine goes right from 14.7 to 12.8 without the intermediate steps, and sometimes it starts at 12.8V. Ugh. Still crossing my fingers that my 48V doesn't die.

 

This is just my assumption but I really think the key for the batteries management is to place the battery charger on the car when:

1) Over a period of time you make a lot of short trips

2) The car sits multiple times for extended periods. I'm not talking months, I'm talking many days or a week at a time.

I believe on short trips the generator doesn't have enough time to properly charge the batteries to where they should be through the 48 volt battery. I believe even when you are at idle at a red light and the DC/DC voltage converter for the 12 volt battery charge says 12.8V on the screen, there still is not a proper charge going into the battery because the 12V AGM battery says I'm charged but the car is still using power from that battery. Over a period of time, the battery will sometime begin to charge but will be down and needs a good run on the highway to do this. if you continue to make short trips over a period of time, the battery will go down to the point where it may be critical or until the battery says I need a charge. This is why I believe shorts runs don't really charge up the batteries the way they should so this is why I believe it's a good idea with the CTEK battery charger. I do live in a small community and I do make a lot of short runs. I don't go out everyday so the car will sit in the garage. I'm retired.

I did have a situation where the car sat for a week and when I came back I placed the battery charger on the posts under the hood for a day. The 12 V battery read 12.4V. These AGM battery are fully charged at 12.7/8V. This time it took 6-7 hours to go through the 8 stages to float. I believe the charge is also not only going to the 12 volt battery but also charging 48 volt battery also. This is why it takes longer.

If a person commutes longer distances everyday for work or on freeways a lot, this situation could now be different. A 100 mile trip could make a difference for sure. Personally, I would try the battery charger on a time to time basis just to help keep them topped up and help with the management of your batteries. It doesn't hurt and only helps. Might as well put it on overnight. A staged battery charger like my 5.0 CTEK for example puts out 4.3 amps and voltage changes in the different stages until float. The charger will not overheat or over charge the batteries. I have noticed when I take the charger off and let the car sit say for overnight, the charge on my meter on the posts under the hood sits at approx 13 Volts. I believe there could be a reverse current flowing from the 48 V battery through the converter to the 12 V battery and keeping it at this level. Level will be lower as the car sits.

Anyway, I don't know if my assumptions make sense but this is what I'm doing and thought I would pass this on. The owner's manual even says it's a good idea to put a charger on the posts under the hood if the car has many short trips or is sitting.

I think your voltage regulator says at start we'll put in 14.8 Volts to start and quickly realizes the battery is charged for now and changes the charge to 12.8 Volts. If we had an alternator, it would do the same thing.



Toban

 

Hi,

That's exactly what I do with my CTEK charger. Great minds think alike.

I was just out driving and when the engine stopped at a red light, strangely enough, the volts stayed at 14.8..

thanks.

 

Toban, that is a good explanation and recommendation to preserve the battery. I do the same if my GLS sits for more than a week.

Jtjbt20x, when it reads 14.8V and the engine is not running I believe it is because the 12V battery is being charged by the 48V battery and does not need the engine to run to do this.

 

I think we all know more about this subject than the dealers know! Most Brand Ambassadors (salesmen) have not a grasp of this system at all. One salesman told me the generator was this thingy thing attached to the top of the motor? I just looked at him.

Toban

 

Now that's getting technical!

 

Does anyone happen to know if there's a way to identify the "bad batch"? I've had two bad 48V's in my car's first 731 miles, and the dealer will be replacing it again. I hoping the third time is the charm.

 

A part number with a service order was posted earlier in this thread. It’s very unlikely that Mercedes is shipping the old ones now that they have a revised one. Beside ticking off the buyers, it costs them a lot of money each time there is a failure. There was probably a time window that they had no alternative but to replace failures with the old PN until the new ones became available. All of this is conjecture on my part.

 

Does anyone know if the 48V battery is covered under the MB extended warranty? Since it is part of the powertrain, I'm hoping it is covered?

 

I was told be the GM at my dealership in Canada the EW does not cover the batteries. Others have said it does who live on the USA so check with your dealer. The sales people will not know so you should check with someone higher up for an absolute answer or read the extended warranty coverage for yourself. Look for batteries in the list of coverages.

Toban

 

I was told about 6 weeks ago that MB were not shipping out any of the old 48 volt batteries anymore. This was in Canada so I have to think it’s got to be North America.

Toban

 

I got my car back today, basically after two weeks in the shop. Since the dealer had no loaners, they payed for a Hertz rental for the duration.

The dealer had no literature to provide showing the 48V battery is covered under ELW. Their service writing software says that it is covered beyond 50k miles with my policy. They told me my best course of action will be to contact Mercedes Customer Care to get coverage in writing. They seemed a little taken aback that I would be so adamant about finding coverage limits of this ELW. Every part on this car should be defined as covered/not covered, especially when it costs $4k+ to replace.

 

It's absolutely unbelievable but not surprising the dealer doesn't know and wouldn't even offer to find out for you. So, if they couldn't find anything in their brochure or paperwork showing it covers the battery after the 4 year warranty is up, the answer is NO. Wonder if the business manager who sells it to you would know? Bet he or she doesn't. I can tell you if it's not in the printed Mercedes Extended Warranty sales brochure they give you, it's not covered. Now, you pay $4500.00+ for EW and the 48 volt battery happens to go out, it's not covered, The replacement battery costs $2800.00 here and 6 hours labor to put it in, you are faced with another bill more than the extended warranty. Now, you are going to lay out $9000.00.

Get it in writing from somewhere. Obviously the dealer thinks you ask too many questions and probably can't be bothered or you know more about it than they do.
I guess they don't sell many extended warranty packages when they can't even produce any brochures to show you.

My sales manager went upstairs to the GM and they checked it together and came back and said the batteries are definitely not covered.

Go onto Mercedes USA and you will find the brochure under ownership and extended warranty. It spell it out there.

Toban

 

Just went into the Mercedes USA website. You have to hunt a bit for Extended Warranty details but under EXCLUSIONS the first item was batteries.


Toban

 

Thank you Tobin, for your comments, insight and knowledge. Sometimes it helps to get an "insiders" viewpoint. Keep on postin'.

 

If you purchased an ELW you should have a written agreement as part of your contract. This is an excerpt from mine:

 

There is also an additional exclusion for electric drive vehicles. Our 48V Mild Hybrid should be between uncovered normal 12V battery and full Electric/Hybrid battery.6.14. ELECTRIC-DRIVE VEHICLES: Maintenance, service, and replacements of/to the Vehicle’s lithium ion battery are not covered by this Agreement.

I presume our only course of action when the time comes is to petition an early or reliability failure like the other owners experienced during normal warranty period. Lets see what is ELW for the new EQS.

 

Yes, we all know "batteries" are not covered. They are operating under the assumption this means 12V and are telling me as such. This assumption can only harm me, so I'm pushing for an answer as hard as possible.

When I called the Mercedes Care earlier today, they told me they only deal with the factory issued warranty, not ELW. So back to the dealer I call and get ahold of my salesman. I'm hoping to have an answer tomorrow.

The primary issue I have is, how can they sell me a warranty without being able to tell me what's covered? Disingenuous, deceitful, misleading. Had I known there was a 48V battery in the car I would have asked.