I use one deep cycle for all my electronics and my electric downriggers and one combo starting/deep cycle for the main outboard. My kicker is hooked up to the electronics battery and keeps it charged while the main motor charges the other battery. I do not have the 2 batteries connected but I do carry a couple of pieces of battery cable that I can use as a temporary jumper between the two if needed (haven't needed to yet).
By the way UM, don't you think the size of someones rigger balls is something that should be discussed in a less family oriented forum???