Mercedes S320 - "battery disconnect alarm"

I have a 1996 Mercedes S320. I also go abroad several times a year for 2 months at a time. In January I decided to disconnect the battery (in the boot) to save it running down whilst I was away. However as soon
as I took the terminal off the battery an alarm went off under the bonnet (presumably powered by a separate rechargeable battery?). I had to leave the battery connected and on my return this week it was as flat as a pancake!
Can any body tell me, please, how to stop the "battery alarm" from going off when I disconnect in the future?
Many thanks from a newbie.
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Do you mean the burglar alarm fired when you disconnected the battery? Odd if it was not activated.
Where are you keeping the car, would you have the option to connect a trickle charger to keep the battery not running flat?
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First of all... running battery flat is bad for battery. It will dramatically shorten the life of the battery. I suggest you replace that battery for time being.
At the same time, I'd hook up a trickle charger to the car. That way, battery is always fully charged but not overcharged. Get good trickle charger that has microchip to prevent overcharging. There are many of them at all different prices.
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