I have been reading up on the 520T and hearing great comments about this device from experienced alarm installers but I just read an article that makes alot of sense concerning how much of a burden this backup battery can be.
This article claims that your main battery recharges the backup battery any time it needs to recharge no matter if your car is running or not.
If you are not using your car for a period of time and your main batteries voltage drops below the backup battery the 520T module will assume the main battery has been disabled and triggers your alarm.
I was unaware it triggered the alarm, I assumed the 520T would now supply the voltage to keep the alarm active in the event a sensor was triggered.
Does anyone know if this is true or is this old news and they have improved on these problems.

 

The only problem I have with it but its not really a problem is that if you leave the main car battery dead for more then 2 days it kills the back up battery. But thats expected from a sealed dry battery

 

I haven't had a problem with it. The problem you describe doesn't phase me. It isn't as inconvenient as getting your car stolen. I use a battery tender for storing the car. I suppose someone could unplug it but they'd still have to wait a week or two.

If you don't want it to trigger your alarm, don't hook up the blue wire.