should do your job ok there a great battery
how long will it last
http://www.deben.com/lithium-ion/12v-14ah-lithium-ion-battery-pack-with-fuel-gauge.html
1hr 30mins with a 100w bulb or 3hrs with a 50w bulb (with the lamp on constantly). I think I saw somewhere that you can roughly double that with typical on/off lamping use.