For my enclosed trailer, I want to have onboard 110 volts. I have two options. 1st. Generator. Will be installed on trailer tongue. 4000watt continued power, and like 8000watts surge. 9hp engine. about 14hr run time on 6 gallons of gas. About $500. Pros: Pleanty of continuos power for all my needs. Cons: BIG!!!! and LOUD!!!!!!!!!! 2nd. Power inverter. I have a 600watt power inverter, and I have realized that this thing is useless. It cant even power a 4.5amp drill. I have no clue how many watts is 4.5 amps. Sure it will run battery chargers, lights, small stuff. But I need to run power tools, lights, 3/4 hp 15amp GRINDER. Question, how many watts do I need? Ebay has a 5000watt for around $500 and 3000Watt for around $300 Pros: Cheaper than generator if 3000watt is enough...is it enough? Pros: Small!!! Compact, will go inside the trailer. Pros: Quite!!!!- very important. Cons: How much batteries do I need to power this thing and how long will it last? I'm thinking about putting two truck batteries in parralel inside the trailer. Question, can I run two wires from the trailers run away battery so these batteries will get charged with the run away battery, or does the run away battery doesnt get charged? I dont know... What are my other methods of charging these batteries AUTOMATICALly, basicly from the truck power source. Is 2 batteries enough, or do I like need 4? Thanks for all the help.