Mspec33

Hi Guys - I am wondering if someone can help me answer these questions -

1. What kind of battery do I have? LiH or regular Lead or AGM battery? I think its LiH based on the research google tells me its LiH on all GT cars but I cant be sure, can someone confirm?

2. I have two CTEK chargers that pretty much work on every car I have - One is the regular lead battery CTEK and the other one is Lithium US - I tried to trickle charge my GT yesterday - tried the front cig lighter and the rear 12V outlet and in both cases the Lithium US trickle charge (after resetting for 5 seconds as I read on some threads) turns the "stage 7" light on, this light glows for about 30 seconds (Stage 7 light supposedly means the battery is fully charged) but then it goes off. None of the other lights between Stage 1 - 7 turns on which is suspicious since it does when I use the charger on my Cayenne with a LiH battery.

below is a picture of the Lithium US CTEK ("stage 7" is the one that is not lighted and has the picture of a battery.

So my question is do I need a different charger or is there an issue? I dont feel like my battery is fully charged (as the stage 7 light implies) because I dont drive the car often enough and even though the car works fine I am always worried about battery life!

logo)

wildta

I believe the newer models can only be charged via the jumper post and the positive connection hidden under the red slide cover in the engine compartment, unless you install quick-connect battery leads elsewhere.

streborx

12V accessory sockets can be misleading. Some remain active for a few minutes after shutting off the car, and then are switched off. Connecting a charger to a 12V socket that behaves this way is not going to charge your battery. As earlier posted, attach a pigtail connector to your jumper terminals in the engine compartment and plug your charger into it.

The lithium setting on your charger is not for charging 48V lithium batteries in mild hybrid vehicles. It's there for people who want to spend $1,000 on a 12V lithium starter battery, such as an Antigravity brand unit, to replace the OE 12V AGM battery.

Mspec33

Are you referring to this? the black cover does not move but I do see the positive sign - how do I move forward?

wildta

You should consult your manual under battery in the index and there should be a picture of the negative terminal post. Underneath the red sliding cover is for positive connection only.

streborx

Yep - that's the +12V connection designed for a charger alligator clamp. Connect negative to any chassis bolt (although there should be a close-by ground lug.

If you remove the large plastic cover, you should see this +12V terminal connected to a terminal strip where you can wire in your charger's pigtail connector.

wildta

I didn't know that! Definitely going to install my pigtail now. Thanks.

Googled and found your negative post here @Mspec33

OldManMotoRacer

Hi all… newb to forum and first post… as I sit here waiting to the tow truck to take my 2021 GT43 to the dealer for the FOURTH time in 6800 miles to correct the “low battery” warning that freezes the car won’t let me start it or even put it in neutral.

I’m very familiar with trickle charters and lithium batteries, AGM and plain ‘ole lead/acid but I have ZERO experience with this 48v “helper battery” thing.

Has anyone been successful at charging it from under the hood as shown in prior posts? I tried using a similar Ctek 12V lithium charger to no avail.

im informed that our 48v helper batteries are a collection of smaller cells (I can’t remember if they are 4.7V cells or what but something in that order of magnitude). I’ve not found ANY data on how to service this issue other that taking it to the dealer. Which is obviously a huge headache.

According to the dealer it’s the BMS system getting upset to a single failed cell in the 48V battery. But they admit that’s just a guess. And that’s through the service rep not the tech. When I go to pick it up this time I’m going to sneak out around back to the service bay and see if I can get the technician to give me some better data because this problem continues to vex me so much I’m considering selling the car—which I otherwise love.

Your experience/thoughts are appreciated.

wildta

I have left my GLE mild hybrid on a battery tender for 10 weeks with no issues. Starts right up and I never get any warnings. I'm leaving right now for 4 weeks and put it on the tender. Just some cheap 4A one with an LCD battery gauge screen showing charging progress that I bought on Amazon years ago for my previous vehicle. Something must be wrong with your BMS or 48v Battery pack. Is your 12v battery lithium or lead acid?

Hopefully the dealer figures it out. Keep us posted.

streborx

I own hundreds of battery operated devices, and the most complicated of them (such as the rechargeable power tool batteries) have temperature sensors that control charging action. Nothing I own has a battery pack enveloped in an isothermal jacket with active heating and cooling as do these mild hybrid 48 volt batteries. This implies that (a) the battery is deployed in a hostile environment where it can otherwise not perform its purpose, and (b) the battery is being aggressively charged and discharged and requires induced cooling in order to safely function.

These mild hybrid systems are reputed to provide up to 10% improvement in fuel economy if your driving comprises substantial stop and go activity. Otherwise, your fuel savings occur while your car is being flat-bedded to a dealer's service bay by a CO2-spewing diesel powered truck.

But what really annoys me about these mild hybrids is that this non-essential acceleration assist system completely cripples the vehicle when it develops a fault, and the only reason for this is regulatory. Manufacturers score EPA fuel effiency points with mild hybrids, so the system cannot be disabled or left non-functional -- the entire car must halt in its tracks until remedied.

This insanity is why I'll never own a mild hybrid. I have my last new car purchases parked in my garage right now.

OldManMotoRacer

Thanks for the replies. I was a motorcycle racer and have extensive mechanical and electrical experience. I probably have two dozen vehicles on various trickle chargers this moment. This isn’t a newb error.

1. hostile environs. Vehicle is garaged in the Bay Area of California in temperate climate and is my primary daily driver. It never is subject to “hostile elements” save perhaps for the first month after I bought it from the Honolulu dealership when it lived in the warm climate of Oahu, Hawaii and functioned perfectly while in the island. It was about a year after being brought over on a boat to California the first error occurred.

2. Overcharging/owner mischarging. It never spends time on a charger because it doesn’t need to… save the times this battery error has occurred.

3. It’s with the dealer now. The service managers response was “oh yeah one of these again” as if it was a regular occurrence but shed no light on the issue. I’ll know more when I can talk with a technician.

OldManMotoRacer

I love love love driving the car but if I’d known it was essentially a hybrid I never would have bought it. Batteries have a finite lifetime and fail. My 69 coupe is still running strong this minute on its original motor and transmission… even Mercedes doesn’t build them like they used to…

OldManMotoRacer

Correction: the only time my 2021 GT43 has spent time on a charger is when this error occurred. And even after 24 hours on the correct CTEK charger mounted on the front posts as described earlier in this thread the car continued to exhibit the errors previously posted, wouldn’t start, wouldn’t even permit me to put the transmission in neutral.

And it is painful to see a Towtruck drag an all wheel drive Benz 26 feet on its winch up the flatbed instead of using skates or wheel dollies or the like… taking it to the dealer repeatedly for this is unacceptable. If I’d bought it in California I could invoke lemon law but I bought it in Hawaii… maybe I’ll check Hawaii law on this. But ideally I’d just want to see the problem corrected. If anyone knows of the proper way to charge these 48v systems I’d love to know it.

My brother is an electrical engineer and tells me the 48v battery is most likely a collection of 3.7v lithium cells and I should charge it as if I were charging a 3.7v lithium battery but I’m hesitant to experiment in this way because charging a battery improperly is a good way to destroy it.

So anyone with knowledge on how to properly deal with the 48v system, your advice and thoughts are welcome. Thanks !

OldManMotoRacer

Oh and I have several of the very expensive antigravity lithium chargers because I run their batteries in the race motorcycles. But despite the speculation that I should use one of those chargers in this thread I haven’t tried it on the GT43… right now the car is with the dealer but if anyone has actually had success with this method I would appreciate hearing about it.

I don’t know if the correct charge is ~750mA at ~3.7v or something like that… but I understand for 48v golf cart batteries people push up to 2 amps at 52v (not 48v for some reason?) but I’m hesitant to experiment with this car for fear of damaging this stupid 48v battery.

Again any experience appreciated.

streborx

I have several Noco chargers that accommodate 12V lithium batteries, such as the Antigravity brand. The 48V lithium battery used in the mild hybrid equipped vehicles is charged through the vehicle's ISG regenerative braking, or alternately through the 12V battery management system, AFAIK. I am not aware of any direct charging of the 48V battery method or any recommendation to do this.

OldManMotoRacer

THANK YOU! For the most useful information on this issue I’ve received so far. This would explain all the symptoms I’m experiencing. I seldom drive the car enough to adequately perform *any* function with the brakes… let alone charging a 48v battery.

1. I don’t commute and 99% of my driving takes place in a one mile radius in a town that doesn’t have a single stoplight.

2. I drive like a motorcycle racer… (shrug) that means I go SLOW on the street (racetracks are for going fast) so I never ride the brakes… no trail braking into corners… on the street I barely touch the pedals at all… I don’t think I’ve ever even put the accelerator down past 3/4 of the way because I hate stopping for gas… and I’ve gotta say I’m impressed with the fuel economy on this car. It’s night and day compared to my cars with V8’s.

and you can see from the mileage that in 3.5 years I’ve put less than 7k miles on it…

so… I guess this means I need to go on one aggressive drive once a week to keep that 48v battery charged up…



PS I have a ton of those noco chargers—I agree they work great.

wildta

I've never done this but there's a way to see the level of charge of the 48v Battery via a workshop menu. See here for example:
https://mbworld.org/forums/cls-coupe...ml#post8718256

I have read that it charges fairly quickly with the regen braking. Once you figure out how to access the menu, I'm sure you'll figure out how long of a drive with some good regen braking you'll need each week to fully recharge it as you monitor this screen.

OldManMotoRacer

Thanks!!! Super helpful!

Mspec33

Did you ever get any additional updates to your situation? I am baffled as to why I am not able to trickle charge this car through the regular 12V socket...

streborx

12V accessory sockets are disconnected (sometimes several minutes) after shutting off the ignition. If there's no power to the socket, you can't charge through it.

OldManMotoRacer

No—the car is still at the dealer (stevens creek, San Jose FWIW). Thanks for the reminder that I need to follow up with them. The prior few times I had it in there they resolved it in a day. It’s been over a week… must be my new service advisor… (shrug)

OldManMotoRacer

Agreed—for purposes of this particular car the 12V ports are essentially NOT available for trickle charging purposes. You’ll need to follow the protocol for charging under the hood set forth earlier in this thread.

streborx

Best solution is to buy a quality battery maintainer (CTek, Noco, etc.) that comes with a pigtail connector that you can permanently wire to the charging terminals. Check and double check the connection polarity -- black = ground (-) and red = 12V (+). The connector end that mates with the charger cable is polarized -- you can connect it only one way. This avoids the possibility of ever disasterously connecting the maintainer backwards.