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Let me start with venting about how absolutely worthless the MB G-Class owner's manual is. It's not worth the paper it's printed on much less the 5.6 MB of storage it consumes on my PC's HDD. The section on the battery starts with 4 pages of cautions, warnings and advisories, and then states regarding replacement of the battery "Mercedes-Benz recommends that you have the 12 V battery replaced at a qualified specialist workshop, e.g. at an authorized Mercedes-Benz Center." Then there's another half-page of notes regarding if you decide to replace the battery yourself, but absolutely no indication where the battery can be found. Well, here is where to find it -- it's under the cargo compartment floor. To access it, pry the plastic covers off the 4 cargo tie-downs and use a Torx T-40 bit to remove all 4 bolts and washers. Lift the floor panel off and under it you will find the vehicle's battery. There are 3 other modules occupying this compartment: a main fuse block panel (left), a fuel pump control module (center), and keyless entry anti-theft module (right). Despite my criticism regarding the owner's manual, IMO this battery compartment is beautifully engineered. The OEM battery is made by Varta and is MB p/n A001-982-82-08, rated at 12 volts, 92 AHr and 850 CCA's. Battery dimensions are about 35cm L x 18cm W x 19cm H. Both terminals are on the same top forward side of the battery, with + under the red cover on the left. There is rumored to be an auxiliary 12 volt battery much smaller in size that maintains power to essential items during periods of discharge and disconnect of the main battery, but its location remains yet a mystery if it exists. Cargo area with floor removed.
Thank you for the information and detailed post! Does the G have remote posts for jumping or charging under the hood?
There are battery posts in the engine compartment. The + terminal is mounted in a plastic module with a protective slide cover. The - terminal is nearby under another plastic cover whose access is far less obvious. Fortunately there are other large bolt grounding points nearby.
Out of curiosity why were looking for it? Good to know though!
I'm "old school" and simply like to know such things. The last time I experienced a battery failure (just a year ago - a 3 year old Optima yellow top on my Lexus), the battery died unexpectedly and inexplicably due to a shorted cell while parked in my garage. Charging or jump starting was not possible, so I pulled the battery and drove to Autozone (place of purchase) in my other car to get a new one (free - still under warranty by 6 weeks). Mostly, I just don't like dealer service departments and nimrod mechanics.
I'm old school too and I like to know these things too. If the new G is setup like the old one, the Aux battery is located under the main battery. AFAIK, if your vehicle is equipped with either and electronically shifted transmission or the annoying ecco start/stop, an Aux battery is fitted. Look under the truck and see if you can observe the battery well from underneath and see if there is a bump out for the Aux battery.
Thanks for this info. I was guessing it would be nearby one of the fuse panels, so it is close to the fuse panel designated F301-F341 on the passenger outboard knee-wall. This auxiliary battery probably lasts at least 10 years, but I'm curious how it's accessed. The floor panel is fairly well nailed up, requiring the removal of several trim panels. Can it be accessed from behind the glove box?
A bit more info on the main battery. It's size group is H8, also known as 49 or L5. If you ever go shopping for one, most retail store fronts pull up a blank on anything G-Wagon related. Advance Auto Parts carries its Diehard brand in H8 in all 3 of its categories -- silver, gold, and platinum. Platinum version runs about $200. It's also important that it's "AGM" type, meant for cars with start-stop feature (AGM accommodates frequent and fast charge/discharge better). H8 is at least 50% bigger than conventional batteries and weighs in at about 55 lbs. This explains its centerline mounting in the cargo floor. Nice to know I've got 55 lbs. of ballast back there for winter driving.
Good to know about AGM type as well. I bought a Noco Genius 5 battery tender/maintainer a few months ago which asks which type of battery is being charged. My current vehicles also run AGM.
The aux batt or converter is located at the behind the passenger footwell for the 2019 g63. Part# A2059053414
item #220 in pic
I think the modules you reference are just the control modules (e.g., voltage converters) for the Aux battery system. I believe the actual battery is elsewhere. If these were the actual batteries there would be lead (Pb) and other warning labels on them. Furthermore, the electrical connections on them are way too small to handle the currents involved with the start/stop function.
I took a long, hard look under the hood for the mysterious "-" terminal, but I couldn't find it. I have been using the shiny bolt for ground, but I'm curious where they hid the "-" terminal?
Originally Posted by streborx
There are battery posts in the engine compartment. The + terminal is mounted in a plastic module with a protective slide cover. The - terminal is nearby under another plastic cover whose access is far less obvious. Fortunately there are other large bolt grounding points nearby.
Has anyone ever determined if MY2019+ vehicles are equipped with an aux battery? There is not any fuse listed for this, but there is one (fuse #121) for a "Supercap" which could serve the same purpose as an aux battery, and this supercap might be the item mentioned above in Tristanyeo's earlier post.
Somewhat related, I acquired a Noco Genius10 battery charger inasmuch as it has compatibility modes with standard lead acid, AGM and Lithium 12 volt batteries. It also has a 12 volt supply output mode (battery charging voltage is slightly higher) that can be used to power devices requiring up to 10 amps. I purchased a Noco accessory cable that connects the charger to the OBDII connector so that power can be supplied to the vehicle during battery changeout. I used this a couple weeks ago when the 5 year old battery in my Rubicon died. After installing the new battery a few hours later, I found everything had remained intact (radio stations, window operation, who knows what else might have lost its memory).
I took a long, hard look under the hood for the mysterious "-" terminal, but I couldn't find it. I have been using the shiny bolt for ground, but I'm curious where they hid the "-" terminal?
Originally Posted by Hodog16
Love my Noco Genius charger--has gotten me through the pandemic when cars sit for a week at a time.
sweet63: I use that same gold shiny bolt for the ground, I've not seen a labelled negative terminal.
You are both correct. The brass/gold lug is the grounding lug for charging.
The negative battery cable is bolted to a bracket under the un-removable black plastic cover (where the fat cable enters), just above the brass stud in the photo. The brass stud is the chassis ground for charging or jump-starting (as noted).
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