Car Alarm & Vehicle Storage

Don't know about aftermarket stuff but the factory-installed anti-theft could kick in when you try to start the engine. The standard throughout much of the industry is due to all of the many computers' memory circuits drawing from the battery all the time, with a good battery, the engine should still start after sitting for three weeks. That doesn't mean the battery will be totally dead, just that it might not crank the engine fast enough to start.

What I would do, if possible, is leave the hood popped so you don't even have to open the door to get to the hood release, then connect a jumper pack or charger before you try to start the engine. Leave either one connected for five to ten minutes before starting.

Caradiodoc