kretsh

I plan to use a battery maintainer to insure a fully charged battery. Attached are photos of the battery located under the trunk lining - for those thinking about doing the same.

TwinCam

Thanks for the pictures, kretsh. I will be using a CTEK trickle charger when the car won't be driven for a few weeks. It was nice to see the battery location as my 2015 S550 will not be delivered until mid September.

Diesel Benz

If you are not using a fixed installation for that battery charger, it would be much easier to use the connectors at the engine bay.

kretsh

I agree, but I was more interested in learning and seeing the exact battery that I have. In reading the marketing materials, it mentioned "Lithium battery along with weight savings...."

Not sure were the Lithium is, as the battery appears to be a normal lead type battery.

As for the weight savings, since there is now only one battery, that will save the 44 lbs. weight that was mentioned.

I do intend to make a semi-permanent (quick disconnect) connection in the engine compartment. Just wanted to confirm the battery type before continuing.

Diesel Benz

The main battery is an AGM/VRLA battery as printed on the stickers. One could claim wet batteries being "normal" but on an MB I guess the AGM battery is a normal battery.

The car still has another battery, for the Stop/Start system. It is smaller than the pre-facelift starter battery and there must be some weight savings still.

Lithium battery sounds like for hybrid cars?

TwinCam

I looked up battery charging in the 2015 S550 PDF manual and it states the trickle charger can only be connected to the battery in the engine compartment, not the trunk. Likewise, you can only jump start the car using the battery located in the engine compartment. Hands off the trunk battery!

kretsh

That's great to know and much appreciated - BUT, I cannot find any battery in the engine compartment. I've removed the plastic cosmetic covers (passenger side) and found only the "+" jumping post with very beefy cables (behind sliding red plastic door) and the grounding "-" post - no starting battery!

Any other suggestions?

Many Thanks

kretsh

That's what I intend to do.

nyca

Those are the connection points - I doubt there is a "starting battery", those posts under the hood connect to the battery buried in the trunk, those posts are your connection point for both jump and trickle charging. At least that is how other cars with trunk mounted batteries work.

TomS

The main battery is in the trunk. Just connection points and long wires to the trunk up there.

A few pictures of trunk without its clothes.

Diesel Benz

+1 ^^, +1^^^^

When reading the user manuals, it is good to know how the car is actually built. Then it is easier to understand what the manual tries to say.

TwinCam

Thanks for clearing this up, NYCA. The manual does refer to connecting points under the hood, it does not mention a battery. My SL600 does have a battery in the trunk and in the engine compartment, so I wrongly thought the connection points were part of a battery.

kretsh

Thanks for all your comments and inputs. My trickle charger connections will utilize the connections under the hood. I will also be installing an "always on" fused 12 volt "outlet" in the trunk, for times when I want to recharge small items while the car is parked. The existing 12v cigarette outlet in the trunk is a switched outlet, which I want to maintain.

Diesel Benz

Is the trunk power outlet really switched? According to the wiring diagrams it is fed from circuit 30 (that would be always on). Perhaps need to check from the car.

kretsh

I just checked and indeed the 12v trunk outlet is switched.

Just tested the 12v "Jump" connector in the engine compartment to a good ground for trickle charger hookup (12.6 volts was measured).