Electronic Alarms and Home Security Devices - Car battery for extended power loss?

Orignal thread explaining our situation (You don't need to read it to answer my question.)

http://forum.doityourself.com/showthread.php?t=324786

So the junkies that have been stealing from our barn managed to knock over our power pole when they tried to smash the lock off the main breaker box. The pole was apparently on it's last leg and was already rotten.

Our problem is we don't live there, so when we go to put in a new pole we'll first have to get the power shut off. Next we'll have to put up the pole and then have the power turned back on. This could take a few days.

What I'd like to do is hook up a trolling motor or two in parallel to the alarm so it can run for those couple of days. The only problem I see is whatever charger the alarm has built in would be overloaded with the huge internal resistance of these batteries.

I'm thinking if we disconnect the AC power before hooking up the batteries the alarm charger won't be effected.

Am I ASSuming too much?

Thanks - Doug

I don't understand the reason for the trolling motors.

According to the manual the control panel draws only 60 milliamps from the battery at idle and runs the system for 4 hours on a 6.5 AH battery. A car battery should run the system for days. (Remember, a battery doesn't "push" power; rather, a device draws what it needs.)

The usualy caveats about using car batteries in a closed space apply. Especially in a living space!

Yeah, you can use the trolling motor/deep discharge battery, but with some caveats:

The safest way to connect it is to disconnect the AC power, _then_ connect the deep discharge battery in parallel with the regular system battery. Do not disconnect the regular system battery at any point in the process. You may need to work out some creative wiring to pull this off.

Before you reconnect the AC power, disconnect the booster battery. You do not want the system's built in charger to try to push a charge into this large battery.

Yeah, you can use the trolling motor/deep discharge battery ...
Trolling motor battery!?!? I didn't get the inference in the original post. :o

Here I am thinking that Doug planned to use two trolling motors for some weird purpose ...

In my real job (this is my hobby, you know...), I get paid to translate layman to tech and vice versa, so I've gotten good at reading between the lines. When I read the sentence I automatically filled in "battery" behind the "trolling motor". It was the only thing that fit the contex.