I use a Minnkota 30 lb and a deep cycle trolling battery on my V.V. The motor is about 12-15 lbs and the battery is about 40 lbs. All approximate. You can see pics in the gallery.

30 lbs is way more then we need, but it's nice for those long moves. I just moved my frame worward a few inches on the pontoons to compensate for the weight.

I bought a 10 amp high performance battery on e-bay for about $40. Unlike a lot of the motorcycle batteries, it is truely 'sealed'. There are no bags to fill or caps to put on. The only position it cannot be mounted in is upside down. I left it on it's side for 14 days just to check ;-) No leaks! I use it to run my graph and livewell. It will run both for 2 days no problem! It would run my graph and trolling motor all day if I only used the troller in short bursts.