Dear community, since I did not move my SL 350 (2007) for 4 months in winter, I have disconnected both batteries, because of the lack of a socket, and could nevertheless successfully start again in March. My procedure: First of all, make sure that the emergency key (fits in the vehicle key) opens the locked boot lid mechanically! (see also manual) I only did this with the emergency key of the spare key. If it is not possible, you may not Do not close the trunk later! In a collection garage like in my case a problem. Then you need another solution and should not read any more here. If one of the emergency keys works on the boot lid, it goes as follows: 1. Terminal the starter battery in the engine compartment first. 10 key required. First carefully clamp the minus pole, then the plus pole. I have both wrapped each with an old piece of cloth so that it can not come to metal 2. Close the bonnet and doors (not the boot lid) and lock the vehicle by central locking. 3. Now release the consumer battery in the boot and clamp it off. First the minus pole, then the plus pole. Both wrap with a piece of cloth each so that they can’t come to metal. 4. Now you can close the boot lid. (If the emergency key has been tested positively as above) This means that the SL is completely closed and Wint is able to I was worried if the batteries had enough voltage after a good 4 months because I didn’t use any charger. Did they. The spring awakening. 1. Open the boot lid with the emergency key. 2. Connect the consumer battery again. First Plus – then Minus. 3. If you press “Open” on the key, the central locking should work again. With me the the theft siren went on, but after renewed pressure on the key so 4. Now unlock the bonnet and connect the starter battery again. First plus – then minus 5th hood and start the car quite normally. With me a few lights went on and the time was wrong, otherwise there were no problems. Everything worked perfectly. Even the radio stations were still there. The lights went out again after a few meters drive on their own. As I said, so I did it and will do it again next winter. It is just my He But I don’t take any responsibility for other vehicles.