Boat is a 18' Xpress. 90hp Mercury. Two trolling batteries up front. One cranking battery in the back.

Installed Live Scope a couple weeks ago. Hooked both the box and the chart plotter to the cranking battery. Went the last two weekends and wound up with a "low voltage alarm" on my Hummingbird (I use the hummingbird up front for Down Image and Side view). Had both the Garmin and Hummingbird with Radio on. The alarm came on after approx 2.5 hours. and within a few minutes lost power to both displays and big motor was literally dead in the water. I have a Optima "Bluetop" for a starter and troller's at this point.

I am going to unhook everything and take the battery to work where the truck shop can test it with a load tester. If it turns out that battery is good I'm curious as to what my best option would be.

1) What do you all recommend for the best dual purpose battery (Start & Electronic's)?
2) Should I add a battery that and designate to the electronics? If so, what battery for the electronics.

Excited about the Live Scope......Discouraged about the battery issue. I would like to stay with just one battery in the back due to weight, but I want it set up right as well.