Low battery + alarm going off

[Chino]

Hi I have a 2006 is220d with a low Battery. I've had it jump started one but now it's drained so that I can't use the keyfob to unlock the vehicle. 

The problem is that the alarm still works and I can't switch it off. 

If I order a new Battery what's the best way of dealing with this situation without damaging anything, going deaf or having a constant alarm going off.

Thank you!

James

[Herbie]

Disconnect the Battery, even take it out if you want to.

[NemesisUK]

Does the alarm have it's own back-up Battery?

[Chino]

Hi NemesisUK,

Yes......I've just found out. When I disconnect the Battery there is a lower volume alarm coming from the rear.
There must be a back up? in the rear?
Guess what? The fob doesn't work so I can't open the boot(!)

Any clues?

I'm ordering a new Battery tonight but it would be nice to work on the car without going deaf.