Way back when I worked for a battery and alternate power system company, what we would do is setup an inverter / charger (Tripp-Lite is what we sold, something like:
http://www.amazon.com/Tripp-Lite-APS...verter+charger) with two golf cart batteries (look for deep cycle GC2 batteries) or Optima batteries.
The batteries would go inside a plastic battery box, like:
http://www.remybattery.com/Group-Siz...Box-P1987.aspx. We would put the inverter / charger on the top, bolted to the box.
Wire it as appropriate and you have a very nice unit that (based on load) can run for days. We setup an expanded version of these up in Alaska (more batteries) and had where folks could run their cabin all week, with a generator running on Saturday to charge the battery bank, run the clothes washer / dryer, and fill up the cistern with water. It worked all summer and winter.
If you want to go bigger than a couple of GC2s, run an 8D sized battery in a larger case. You will only need one, as it's 12 volt (where as the GC2s are 6 volts a pop). Be careful, these are very heavy.
GC2 batteries provide approx 180 to 200 amp hours.
8D batteries provide 225 to 255 amp hours.
Be sure to select an inverter / charger that is appropriate for your situation. Look at the amperage you need to support and the voltage the selected batteries need.
If you don't have a ventilated area, you may want to consider sealed / gel batteries.
The nice part about this is that it can be easily charged with a couple of jumper cables if power is out for an extended period (you do want to disconnect the batteries prior to connecting them to your vehicle).
Finally, don't use a surge suppressor connected to the inverter.