SL55 - Is there any way to power the consumer electronics from under the bonnet?

[epicnerdrage]

Hi all, my consumer battery was dead from lack of use, so I took it out to charge it and closed the boot. However, my key blade doesn't work (it just spins, so its not connected inside). Great.

I would be able to open the boot if I could provide power though, is there anyway to hook up the consumer battery with some jump leads to somewhere under the bonnet so that I can unlock the boot? Or would starting the car provide power? I am loathed to open the doors until I know, as the windows wont properly lower and reseal so my car will no longer be water tight (and its outside). I do know I can open the boot by breaking the rear 3rd brake light, but that seems excessive, and there surely must be a way to power that circuit from somewhere else in the car...

Any ideas?

 

[grober]

The main power lead connection to the starter motor comes direct from the battery so connecting a 12v supply jumper to that connection and the negative jumper to a decent earth [ a battery charger will do - don't try to start the carr!!!]should give enough power to unlock the car---thats assuming the loose battery positive connector in the boot cant short to earth- you will need to crawl under the car to do this

 

[whitenemesis]

Some training/background info on the dual battery system in the R230

 

[alabbasi]

The starter cable might just go to the starter battery but the cable from the alternator should charge both batteries. These cars are a pain in the ****, even my smart charger doesnt like it and needs to be recycled to keep the battery charged.

 

[grober]

Yes guys had forgotten the 2 battery system on the R230 ALTERNATOR outut lead best bet

 

[whitenemesis]

The info is in the attached doc. The two batteries are isolated by various relays, so no direct connection between the two via any component.
The starter battery in the engine bay powers the starter armature and the systems battery in the boot powers the starter solenoid.
Page 37 says how to start the car with a dead systems battery

BTW the batteries must be disconnected and reconnected in the correct order...

 

[Dickster]

Hi all, my consumer battery was dead from lack of use, so I took it out to charge it and closed the boot. However, my key blade doesn't work (it just spins, so its not connected inside). Great.

I would be able to open the boot if I could provide power though, is there anyway to hook up the consumer battery with some jump leads to somewhere under the bonnet so that I can unlock the boot? Or would starting the car provide power? I am loathed to open the doors until I know, as the windows wont properly lower and reseal so my car will no longer be water tight (and its outside). I do know I can open the boot by breaking the rear 3rd brake light, but that seems excessive, and there surely must be a way to power that circuit from somewhere else in the car...

Any ideas?

I had the same issue, ended up smashing the brake light. And then fixed the lock so the key worked

 

[Diesel Benz]

But OP can enter the cabin and can open the boot, right? Just check the diagram and find an easy to access wire pole that is connected to the rear battery to feed power (assuming the rear battery + wire is not touching ground.