I recently bought a new boat with a 36 volt trolling motor. The boat has 3, 12 volt deep cycle batteries and a single 12 volt starting battery. All 4 batteries are served by a 4 bank charger. The connections were all wrong when I got the boat so I took it all down and started fresh. The 3 trolling batteries are connected in series and are completely separate from the starting battery which has the positive lead connected to a 4 pole battery switch (#1; off; #2; and #1 +#2). I would like to connect one of the trolling batteries to the switch in position 2 so that I have a back-up in case I drain the starting battery with electronics and lights fishing at night. I believe I can safely do that by using the first battery in the series (the one that has the main negative ground going to the trolling motor). I plan to use a jumper cable to connect the negative from that battery to the negative of the starting battery and another jumper cable to connect the positve of that trolling battery to the #2 pole on the battery switch. I believe that will give me 12 volts in parallel with the starting battery when I use position #1 on the battery switch. I don't want to fry anything (either motor or electronics) so can anyone verify or correct my plan?
