hi stylie,
ive used a "rhino" for the past few years very reliable absolutley no complaints.
i used a sports battery (rechargable) the kind used in motor homes, yachts etc. costs more but good for 4/5 yrs easily this was when i was recharging at home.
last few seasons ive used the main outboard wired to the battery so it continually recharges when motoring.
im presuming your going to use this for positioning and moving from drift to drift and stalking etc. and your main outboard for travelling duties. if so theres a few things you should consider.
the size of your boat 17/18/19 ft. and the weight of it when your fishing. the bigger and heavier the more drain on the battery during the day.
bigger trolling motor gives more power=faster travelling.
hope this helps

tight lines