*Batman*

If I were to install an active security device which drains 20mA of current at 12v, how long would I be able to leave my car parked before my battery is unable to start the vehicle?

tommyd3

Most car batteries have at least a 50 amp hour rating. That means you could pull one amp for 50 hours. With only a 20mA draw (0.02 A), you could leave your car for weeks.
I suspect the factory keyless entry system in the car pull more than 20 mA.
I think the age and condition of the battery would be the biggest issue.

I have a solar charger that plugs into the lighter that I use when leaving my car outside unattended for weeks on end.

I8ABMR

I agree that the system itself doesn't sound like its a drainer . The question is what is the condition of the battery. You live in the Florida heat, as I live in the AZ heat, but the dryness here will destroy a battery in less than 2 years sometimes. Make sure you are starting with a solid battery

*Batman*

I bought my car new in May and the battery was new too because I made them change it (its a quirky thing I do when buying a new car).