Fishfinder on the main, or (2)12volt trolling motor?
Just joined forum, lots of great advice here!
I recently bought a like-new 14.5ft Lund and need to add a trolling motor and fishfinder. I bought a 55# thrust Minn Kota and plan on wiring a dual 12v group 27 battery set up in parallel. I also bought a 3 bank 15amp Minn Kota charger and will charge both of these batteries plus the starting battery (I'm lucky to get out once a month, if that). The fishfinder is a Humminbird 798 ci Si, which says it has a 4000watts peak-to-peak power output, 500watts (RMS) output (if that makes any difference).
Question: everything is currently wired up to run off the starting battery (bilge, live well, and nav lights. No radio or anything fancy. There is a fuse panel with 4 unused fuses on the dashboard. Should I wire my fishfinder to the fuse panel and run it off the starting battery (which seems like a bad idea when I'm adding a dual 12 volt system), or use an inline 3amp fuse and wire it to the two batteries that are only feeding the trolling motor? I will be using the trolling motor on a river and will need it pretty constantly for 6hrs or so (thus the 2 battery parallel 12volt set up, instead of one battery).
Re: Fishfinder on the main, or (2)12volt trolling motor?
According to your manual, the current draw on the 798ci Si is only 650 mA (same as my 788ci). In my case, my boat is a little too large for an electric trolling motor (21.5ft Reinell 215c that is 3200 lbs dry), so my second battery is just for accessories.
But I think if I were in your shoes, I would get the largest starting battery that I could fit in the space and connect the fish finder to it as well. I would leave the other two strictly for the trolling motor. I would suspect that the fish finder would still be operating well long after the trolling motor had drawn the batteries down to the point of being useless for trolling, but that extra 5 or 10 minutes may have made the difference. There may also be an instance where you might just want to take the boat out for a family cruise or something. You could leave the trolling batteries at home if you wanted (maybe need the space for other stuff??) and still be able to use your 'bird.
Heck, if you really can't make up your mind which one to use, and if you really wanted to get anal about it, you could run power from both batteries to a DPDT switch on the dash and use which ever one you wanted. Just make sure you don't switch with your 'bird turned on.