mikebodima

Hello

1- can someone tell me exactly what the front battery and the back battery in the trunk do?

2- to open the hard top, it use the front battery or the back battery?

3- can the SL be modified to used only the trunk battery?


Thanks in advance

Vulcaneer

Front battery is used to start the car. Rear battery runs all consumer electronics. And will start the car (in an emergency) if front battery goes dead. I believe the rear battery is used to operate the roof. Question 3....No.

webuycarnotes

http://www.mercedestechstore.com/pdf...2011-28-02.pdf

This was posted by another member some time back. This, and other pdf
training papers on the SL, are also located at: www.mercedestechstore.com

Thanks to all members for sharing.

Also thanks to the member who suggested a look at the AutoCraft Platinium AGM (Part number H6-AGM) battery size H6, 760 CCA that is an exact replacement for the Mercedes OEM battery in the trunk (this is not a lead acid battery).

F1BHP

I have been researching more into the single battery for the r230 and the main problem i have found is that only the starter battery is connected to the starter armature however the aux battery provides power through the starter battery in case of failure using a 15a dc/dc converter. It probably could be done with some new wiring however I am sure it will throw warning codes and probably put you into limp mode.

kfschatz

Fooling around with the ele system is insane!

F1BHP

I ended up moving the starter to the trunk with the aux battery and changed them both to lithium. 4 reasons for this. (1) Better spark from the consistent power of the lithiums (2) move as much weight to the rear as possible. (3) reduce the overall weight by 65lb (4) used the battery space under the bonnet for a small intercooler reservoir/ice tank/expansion tank. Number (4) increases the total coolant capacity as well as making the system much easier to bleed as well as acting as an expansion tank.

Tommyboy928

This SL models, need charge batteri every month ,or have hooked up one charger that charge all the time when parked in garage. if trunk batteri empty, can start car with put key in the ignition. and do not try close the door before engine running.. window will hang on the outside when no power in trunk batteri.

F1BHP

Yep I have a trickle charger connected to the trunk battery with a quick disconnect. The starter battery is charged from the trunk battery via the dc/dc converter.

Tommyboy928

i belive u cant use trunk batteri for start in emercency even.. i was on track with my 2004 sl55AMG, and after some time there, the front batteri shorted out totaly.. internal plates shaken loose. no way the car ever would start, had new batteri in trunk. needed a tow, and got a batteri some days later that fitted small place in front. would think is good idea change the front batteri after 6 years,just to be shure no surprices

F1BHP

I think the front battery has to be functioning in a normal way for the aux battery to provide the power to it. So if the front battery is short on cranking amps to start the aux battery will boost it sufficiently but it is not connected to the starter armature so cannot start the car independently. So in your case when the battery shorted this would not allow the aux battery to provide backup power.

Vulcaneer

Yes....This is my understanding as well. If the front battery is not strong enough to start the car, the rear battery will supplement the power enough to get it started. Such as if you front battery ran down for some reason.

But if the front battery was shorted, the rear battery alone cannot provide power to the starter. The rear battery needs a functioning front battery in order to assist in emergency situations.

brownboy

I was stranded this week from the car not starting. Had the red battery warning. Enough power to operate the windows and trunk but not start the car. I had both batteries replaced 25 months ago. Unfortunately that put me 1 month past their warranty and unfortunately the back battery did not start the car.

Every battery I have owned (car, laptop, phone) has let me down.

F1BHP

Brownboy I am suspecting that you did not replace them with the MB batteries. The rear is a AGM battery and will last between 5 and 7 years with no problem. It is worth paying a little more to get.

brownboy

Both were MB batteries and the dealer said they would have been replaced for free if they failed within 2 years. Guess I just had bad luck or maybe I should I use a battery tender though I drive once a week.

F1BHP

If you are only driving it once a week then you should definitely have a tender. I installed a quick connect to my rear battery for easy access.

Extreme Dimensions

Don't mess with the ELE, I blew one out trying to install some HID (don't ask) and it was a costly fix.

brownboy

I'll consider the tender but I'm in a condo building and don't have an electric outlet closeby. Just got the car back yesterday. They replaced the front starter battery and said the rear AGM one was fine. If that's the case why didn't the rear one start the car? It would have been nice if it did that and gave me a warning so I could have driven to the shop instead of waiting a few hours for the tow. Any sort of warning would have been nice. When I couldn't start the car there was enough power for the trunk closer and windows.

F1BHP

Probably something wrong with the starter battery not just that it was low. The trunk battery will support a healthy battery that has lost charge but cannot help a bad battery.

kfschatz

I have a 2007 sl550 and when both of my bat failed I could not get the car to do anything with keyless start button on the shifter. When I put the key into the ignition switch and turned it, it started.

F1BHP

Did you check the battery in your remote