I run a 998 SI up front and a 788 on the back. Experience very minor cross talk on 2D on the 998, but higher chart speed spreads it out and if it starts annoying me or I want to take pictures I just turn off the sonar on the 788. For a battery, I would get a 35AH gel deep cycle battery like made for powered golf caddies, easy to handle and will not take up much room. I use them to power underwater lights night fishing.