I was wondering if it was possible to use, simultaneously, a 30 amp (or higher) charger on a car battery and a DC to AC (say, 700 watts) power inverter. Where I live we have 8 to 10 hours of power outages in 2 hour intervals during the day. Instead of wasting money on expensive office UPSes, I was wondering if I could make something a bit more sturdy using cheaper car batteries. What I wanted to know is, how fast would a 30 amp charger take to charge a car battery? And how long could a car battery deliver 700 watts? I'm a complete n00b here so if someone could point out the specific formula/equation to use to calculate this, I would greatly appreciate it! Ideally I would like enough batteries (I could just hook up a bunch of them up in parallel?) to deliver 700 watts for 4 hours, that would then recharge within 2 hours (when the power's back on). Lastly, does anyone have tips for actually setting up this kind of apparatus? Specific parts/companies?