::blinks:: the battery would die with in minutes, 5 minutes max of power and that's if the charger keeps it really nice and charged. Best bet is to use a deep cycle Optima yellow top battery, it's used for high end audio systems in cars, also a capacitor would be needed.

Instead of 20amps go with a 40 or 50 amps. I would do parallel so you don't end up hurting other power devices.

Get rid of the lamp, cable modem/router and speakers. The UPS system is there so you can save your work and shut the system off, it's not meant to run the system fully off of battery like a laptop.

If thats what your trying then get a generator.

heh, yea. Well, I like the router/cable modem on there so I can shutdown the main rig and continue doing work from my laptop for hours. Since cable doesn't need power to be sustained, internet will stay up most all the time.

As for the light, I turn it off when power goes out. Its just nice to have connected so I can use it when powers out

As for the time being min, yes, I know, I get like 3 min now tops!

You mention a CAP. What would be the point? Isn't a CAP just a battery?

The cap takes the strain off the battery. Heres a example for a car.

Battery - Cap - Amp - Speakers

That's how most people do it. Now for my setup when I had the car running and before my carputer was stolen.

Battery - cap - carputer - Amp - speakers

The battery charges the cap and from the cap it goes to what ever device you connect it to that uses high amps and wattage.

I have installed CAPS before, and I am aware of how to use them. However, it was my knowledge that when the car is running your alternator is designed to push the electronics of your car at 14 volts. So, you have about 2 volts of extra there beyond keeping the battery charged. The purpose of the CAP is to handle the spikes needed by the amp at times when the alternator can't keep up. This keeps the car battery from dying and your lights and other electronics inside the car from being drained of the power they need.

Now, I don't understand how a cap is going to benefit me. As I understand, its just a small battery in the connection closest to the power source, to prevent drain on the alternator...

Most alternators these days have a voltage regulator that won't let you exceed over 12 volts. Lets skip the cap idea, I wasn't thinking correctly at the moment.

Wonder why your Voltage Meter on your gauges reads 14 then?

Mine reads 12.6volts and the voltage gauge in the car reads 12.

Anyway, after thinking about it would the APC be able to charge a car battery and keep it charged?

I don't know the answer to that... I don't know how the onboard inverter/charger is setup...

here is a good article...

http://catbear.livejournal.com/186573.html

I've done this mod. It's quite useful. I got 36 hours of power off of two wheelchair batteries wired in parallel. I mean... I was only running a laptop and an external HD.. so the draw was about 130W or so at load.