My 2013 GLK 350 displayed the Auxiliary Battery Service notice the other day and when I searched here and the internet I still had some questions. Hope this helps.

MB OEM Battery Specs:

OEM# A 000 982 70 08-Q3

12V 12 Ah 170A (EN)

5 7/8” L x 3 7/8 W x 5 11/16 H

The battery is in the aft luggage area. To access the battery I would first suggest you clean out the rear area and let down the back seats, it will make this process easier. Open and remove the spare tire cover and any mats/covers in the way. Optional: Pull the spare tire (~30lbs) at this time, I always seem to drop something in there.

1. Tools: Ratchet, extension, 10MM socket (deep would be better), 40T Torx bit. Optional: Flat screwdriver.

2. The battery cover you will need to remove is on the right side of the well and runs from under the carpeted panel, with the two D-Ring cargo net attachments behind the back seat, to the finishing strip at the back of the luggage area. Pics # 1, 2.

3. I removed the two D-Ring cargo net attachments on the carpeted panel behind the back seat to ease the removal of the molded plastic battery cover. The black plastic covers for the D-ring hinge and fasteners may need some gentle prodding with a screw driver to access the Torx screw. See pic of black plastic hinge covers and D-ring fastener. Pics # 3,4.

4. On the right is a tray I keep small stuff in, remove the rubber tray bottom liner (has a small tab to pull it out easy) to expose the two Torx screws and 10mm nuts on the other side you will need to remove. Two metal grommets will fallout of the holes now or when you pull the battery cover out. See pic #5, 2, 6.

5. The cover should come out easily and the battery is easily accessed from there.

6. Reverse steps when done.

7. I installed a CTek Charging pigtail because when I tested the the battery it still took a charge. So I thought run a little experiment. I reconditioned the battery with my CTek, charged it and reinstalled it. I used the car today and the code reset, so we will see longer term. Pic #7

8. If you what’s to see under the carpeted panel with the D Rings. Pic #8.

Note: I have no Idea what functions this battery supports either.



#1 Battery is Under Here

#2 Battery cover removed

#3 D-Ring cargo net attachment

#4 Cargo net D Ring and Hinge cover

#5 Tray bottom Rubber Liner

#6 Two Metal Grommets

#7 CTek Charging pigtail

#8 Whats under the carpeted panel with the D-Ring attachments.jpg

 

Thanks for the How-To ... good reference !!

From the MBUSA website :

Auxiliary batteries work with your main starter battery, and as a backup battery in the event the main battery becomes disabled. It prevents your vehicle’s electrical components from dropping when starting/stopping your engine and keeps your radio, GPS, and other in-vehicle electrical components turned on.

 

Thanks for the kind words and info. I had seen this battery when I installed my Westfalia hitch and figured it was for maintaining/storing some presets but this seems a but much to expect from a battery this size. Regardless I should have known considering past experience with this MB. Thanks again.

 

Hello everyone, I'm not very knowledgeable about cars but I've learned a bit reading about my problems, From tweaking connectors or reprogramming the main panel using the key in the ignition. My driver seat used to move back, the stearing would lift up and a light under the door would go on when the driver door was opened.
Suddenly, the seat won't move back nor forward according to the memory settings, nor the light under the door would go ON. The stearing still lifts up when I open the door but that's it.
The auxiliar battery was replaced and the fuse yet It wouldn't fix the issue.
What else can I do besides taking my car to the dealer, pay $275 to diagnost the problem, and Then who knows how much more to fix it?
Any more suggestions before I must break the piggy bank? Thank you. Sonia

-----------------------------
From the MBUSA website :

Auxiliary batteries work with your main starter battery, and as a backup battery in the event the main battery becomes disabled. It prevents your vehicle’s electrical components from dropping when starting/stopping your engine and keeps your radio, GPS,
and other in-vehicle electrical components turned on.[/QUOTE]

 

Presets, such as seat/mirror position, steering wheel position, radio presets, climate control etc. etc. need only tiny amounts of power - think "coin battery." Mind you that's just saving position or settings in memory and not moving a seat, for example, back to the saved position. A battery the size of the Aux. battery could save memory presets for about a billion years... Not saying that the Aux. battery is even used to save presets in our vehicles - I simply don't know.

 

[/QUOTE]

Not long ago, and just for fun, I did a test on my 2014 GLK350. I disconnected the main battery to simulate a complete failure /discharge. The relatively new and strong auxiliary battery did nothing. In other words, it powered nothing obvious. Not the display, not the windows, not the radio, not the mirrors, not the locks... I don't think it's there for that. I believe that's completely normal. The Aux. battery purpose seems to have varied over the years regarding its "responsibilities" depending on the model and the time period. From my understanding, and experience, the Aux. battery in the GLK is there for the Eco Start/Stop functionality (keeps most/all of the other stuff running when the engine shuts off at a stop light, for example) and to assist the main battery for engine start when the main battery is weak/has a low charge.

 

From my understanding, and experience, the Aux. battery in the GLK is there for the Eco Start/Stop functionality…[/QUOTE]
The auxiliary battery in the GLK is there to run the auxiliary transmission pump which is required to enable immediate drive off after ECO engine restart.

 

The auxiliary battery in the GLK is there to run the auxiliary transmission pump which is required to enable immediate drive off after ECO engine restart.[/QUOTE]
yea they aux battery is a jioke and a waste of everyone’s time

 

OOPs

 

[/QUOTE]



As you can see it is probably not the Aux battery. That said I would hook up my OBD2 scan tool. It will not tell you every thing that the one the MB mechanic uses will but it will tell you enough on most cases. I use an Innova and paid about what the dealer will charge for doing it once. E.g.
1. Main battery coded and I could check to see if was an alternator problem but I just changed the battery (they are heavy lol)
2. Right wheel sensor failed and the warnings were many and varied and the car went into limp mode (scary and overly dramatic imo). I changed the sensor. (I needed a jack and stands for this, oil changes, replacing the discs on the brakes. BTW the tires are very heavy)
3. Left wheel señsor failed two months later. See above

I scan at least once a year to see if there is a potential problem. Or sooner as needed but you see my point. How deep you get into this is up to you but just knowing is enough or at least a start for me.

 

Thank you this was a good write up

 

Thanks! I hope it helped.

 

Not really important ... I've responded to a couple threads about "Aux Battery Malfunction" on dash.
GLK runs fine even with the "malfunction"

No, i dont use ECO .... turn it off when I turn key on, but I'm annoyed by the message every first start up.

Anyway, my O'Reilly's Parts near me had a Super Start battery in stock, so drove up ...

Removed the orig Aux Battery in the parking lot (took less than 5 minutes), walked in, bought new battery ($125), installed new (saved a core charge) ... made numerous stops after install ... no more Aux message on dash !!

Original battery I removed was dated 2013 ... we'll see if this one lasts the same (kinda doubt)

 

Just updating the results from the first reconditioning effort on the original Auxiliary Battery (used Ctek MXS 5.0) I attempted on 9//3/22 post. The battery threw the Auxiliary Battery Service notice the last week of April 2023 so it is time to replace it. Good news is it lasted 10 years, but it does not seem to resurrect all dead batteries for long.
The original main battery lasted 4 years (with no reconditioning) and 44.2k miles. The replacement is a [size=13px]Bosch Platinum Series AGM Battery Group[/size][size=13px] Size H7/L4/94R [/size]MMJ25 its @ 6 yrs this month with almost 20k miles and annual reconditioning. We will see what happens.

 

For those interested in "What the Hell Does It Do?".
1. The only thing I noticed before replacement was while driving was one rough shift and my MPG jumped to the 80’s and slowly decreased to more normal numbers.
2. Charging: Will update this afternoon

[size=13px]I replaced the axillary battery with an EverLast CTX14-BS ($49.99) on Amazon.[/size][size=13px] [/size][size=13px]It is12V 12 A 144 Watt AGM[/size] with[size=13px] battery dimensions of [/size]5 7/8 L X 3 7/16 W X 5 3/4 H (see OEM specs on my 9/3/22 2013 GLK 350 Auxiliary Battery Servicepost). It allows cables to top or side mounting with current hardware and supplied nuts.
Access and removal of the old battery is detailed in the 9/3/22 2013 GLK 350 Auxiliary Battery Service post.

The EverLast CTX14-BS is dry shipped with the acid in six (6) individual contiguous bottles of battery (sulfuric) acid.

Pic 1: CTX14-BS Electrolyte Bottles
The directions are clear and easy to follow but it is suggested no smoking and wearing safety glasses or face shield and hand protection like nitrile gloves. I added the acid outside in front of the garage, the biggest problem was keeping the bottles level. There may be some difficulty piercing the foil so light taps on a small block of wood with a rubber mallet might save the old meat hammer

Pic 2: Electrolyte Install Tools

The directions do not indicate that the battery will get warm to the touch when the acid is added but after about 20 minutes it will begin to cool down. The bracket for the battery will cover the positive and negative markings embossed on the battery so some red nail polishI mounted it in the battery carrier at this point and hooked it up to my CTEK (MXS 5.0) charger. EverLast estimated charge time is 6-12 hours and its 12+ with my charger.

I wire brushed the posts and gables then applied some dielectric silicone grease. A small flat blade screw driver less than 5” long will be helpful to apply grease and hold the nut in places you install the cables. Other than that reassembly, is the reverse of the 9/3/22 2013 GLK 350 Auxiliary Battery Service post.

 

An AGM battery is what’s specified. Not what you purchased . AGM won’t leak in an accident or off gas corrosive hydrogen that will corrode battery terminals and maybe more. But I’m sure you will be fine.

 

I don't know if it's a legality or not, but if it's not a sealed battery you have to have an external vent both for safety and to prevent the inside of your car from corroding away. Flooded cell batteries vent hydrogen gas. Remember the Hindenberg!

 

I believe it is an AGM based on the manufacturer website http://www.everlastbattery.com/produ...w-x-5-3-4-h-4/

But thanks for the heads-up

 

I appreciate your concern but it is a sealed AGM, you seal it after you fill it. Out gassing hydrogen is minimal with AGM batteries http://www.everlastbattery.com/produ...w-x-5-3-4-h-4/

I'm not that old but I had a vivid reminder in 1968. One of the students in my semi-micro qual lab thrust a glowing splint in a gallon of hydrogen gas. The rubber stopper embedded in the ceiling and glass fragments flew by me. The Professor was pissed and oddly speechless at the same time.

 

Wow! Never encountered one of those. Even an old fart like me can learn something new!

 

If no liquid comes out when tipped over, with its caps off than maybe it is AGM

 

The directions specified 20 of more minutes to add the battery acid and an additional 20 minutes to insure the acid is absorbed in the mat but I did not that test to see if it had. It's OBE now.

I guess it could be a gel battery. It is listed on Amazon also so maybe they know more. I only saw conventional and AGM listed on the EverLast site but I could have missed something.

 

If you can’t see lead plates stacked side by side, you have an advanced battery, AGM or gel. It is interesting Acid was shipped DIY.

In my limited battery knowledge, that gives you the best , freshest, new battery.

and probably the least liability for shipping Acid.

check charge on it . It should be high at near 12.8-13 ( I’m speculating) but I’m thinking it’s (really new)

I won a non payment case on Sears for selling me an old battery that took about a day to charge . ( I canceled the check because the battery was old )

check out Bluetooth battery monitors from CTEK and others . I use them

 

I CHANGE GLK 350 ALTERNAOR AND IS DOING LOW CHARGING AND PUT MORE THAN 4 ALTERNATOR WITH THE CAR , IS THERE ANY HELP FROM THIS GROUP THANT CAN HELPFUL FOR ME HERE

 

1) Take the caps lock off.
2) find a thread about alternators and post your question there, or start a new thread.
3) Give a description of the problem and explain why you replaced the alternator 4 times rather than looking for a problem other than the alternator after the second replacement was no better than the first.