Like the title says...I'm looking to have enough juice to power a 360 with a battery or two, for at least 4-5 hours.

My plan is as follows -

Display - Vivitek Qumi projector (85Watts peak) and a large piece of foam bord or similar as screen- http://www.vivitekusa.com/v_display_content_detail.asp?category_id=71&subcategory_id=422&product_id=201

Sounds - Bose rechargable ipod dock. Runs on built in battery.(I have it and its awesome...lasts forever)

Console - Xbox 360 Slim. As far as I've measured, the console does around 112 watts peak and is usually consumes around 75-100 watts.

Power source: AC/DC 500 Watt inverter and 1000 watt, 120 amp/hour 12 volt DC marine battery.

My logic is that 360 + projector do around 200 Watts which at 12 volts works out to ~17 amps. If I have a 120 amp/hour battery, it should power this set up for up to 7 hours(in theory). Understanding that the inverter isn't 100% efficient and that battery may never be 100% full so I'd settle for 5 hours of run time.

So yeah, am I missing something? This should work right?...

I had similar batter and inverter and used it for 2 gaming laptop (17.5" toshiba qosmio) played games for several hrs + we used microwave maybe few times before it died.Going on camping?

i roughly calculated your numbers and it sounds about right to me

Edit: reminds me of this:

lol, yeah. I am thinking it will blow my buddies minds when I whip out a 70 inch screen, projector and 360... :)

Good to know that this should work. Microwave prolly killed your battery a little sooner then the laptops would have. Even small ones use 1000 watts...which is like 83 amps at 12 volts. 83 amps would drain a 120 amp hour battery in less than an hour and a half in ideal conditions.

Cool. will give it a go...

I know the ohms law and basic electrical stuff, but I've never done anything like this...lol