I have a 400 watt Coleman inverter. I purchased a kit that was meant to power a 400 watt amp because it included all necessary connectors, an inline fuse holder, and the right length. It also came with some plastic protective cover for the wire that resides in the engine compartment, and some hardware to get the wire through your firewall.
Works just fine for me. it was about $25, which i thought was a little expensive for a 15 foot length of wire and some connectors. But I guess you pay for the convenience. I just wanted to be safe by using something meant for a car.
The inline fuse is meant to be kept close to the battery in case of an accidental short. I would NOT connect a lenth of wire drectly to the battery without a fuse because you can ruin your battery or set your car on fire (I've seen it happen).