This winter, the power strip that feeds my CTEK battery maintainer somehow got accidentally turned off, and after a few weeks my '06 DB9 Volante's battery died. That initiated the dreaded "Alarm System Service Required" message, meaning that the rechargeable battery in the alarm module had given up the ghost (mine is the "High-Spec" alarm). I turned the power strip back on and the CTEK recovered the main 12v car battery. Unfortunately, the alarm module battery did not recover, and I got the warning light every time I'd start the car after that.
I don't drive my DB9 that often, but I've taken it out maybe three or four times over the past week, and yesterday I noticed that the warning light and message didn't come up. I took the car out again today, and once again there was no light. And yes, I tested the alarm and it works.
I keep my car on the CTEK whenever I'm not driving it, and it's taken care of the main battery very well. I'm surprised that it didn't recover the alarm module battery, but actually driving the car seems to have done the job.

 

Well I have replaced mine with a new one after I got the error message, and I still have the error message... and I have driven the car over 1,000 miles for now.
I assume some kind of issue with the ground connector...