I switched all of my electronics (2 93sv and livescope) to their own battery. Running all of that plus the pumps off the starting batter was becoming a problem if I fish a long day. Running the starting battery down to where it would barely crank the engine. Also, live scope needs at least 12 volts to function properly. Otherwise, the transducer loses connection every few minutes. Not sure what all your running but a 15ah battery will run 1 graph for about 6-7 hours. Reducing by half for every additional graph. Livescope draws about twice as many amps as a single graph. So 15ah would run my set up for about 2 hours. You may not be running that much so you might be fine.