by Ken Cook
a new boat or a replacement trolling motor, the trend is to more powerful straight
24v systems. Most older boats and many of the new ones are rigged for 12/24v
Drawing 1 shows how most systems are wired (left) and how I re-wired my ’86 Cat (right). At the plug end, I used large wire nuts (circles) to make the connections and coated with RTV (silicone) to seal and waterproof. The doubled connections at the battery terminals were accomplished with large, high amp crimp connectors available at auto supply stores. I show only one foot switch in the drawings, but multiples can be used if wired in parallel. A circuit breaker of at least 40 amps should be used on the positive side.
Batteries can be charged with standard chargers hooked direct to each battery (no disconnects required). An on-board charger would hook up the same as using two chargers simultaneously. This should work with the 24v jumper in place, but some on-board chargers require disconnecting it before charging. Read your manual carefully.
Make sure you DISCONNECT batteries first and ASSURE that you don't cross any wires. I strongly recommend identifying positive leads with red or white electrical tape.
This wiring scheme will double current capacity available at the plug and decrease voltage drop by cutting the path length in half. You will only be limited by wire size of plug, foot switch and trolling motor. In older boats, wire size was often 10 gauge and, although doubling it will give significant improvement, I recommend replacement with 6 or 4 gauge. Either size doesn't have to be doubled, but I had previously upgraded to 6 gauge and doubled the wires anyway since they were already in place.
You may take this process one step further by adding a 100 amp marine solenoid to the ground path as shown in Drawing 2. This further minimizes current loss by removing the foot switch(es) from the current path.
Both of these mods have been tested and, if done properly, will work well. There should be an improvement in overall troll motor performance, particularly at sustained high power settings.
The following is a list of things to remember about batteries and charging:
1) If using lead-acid batteries, check the water level regularly. I prefer to use distilled water to replenish levels. Low maintenance batteries must be checked too.
2) Check battery mounts. Assure that hold downs are tight.
3) Check that terminal nuts are tight and free of corrosion.
4) Unplug troll motor before charging.
5) Never connect or disconnect a charger from a battery with the charger powered up. Arcing can cause damage, especially to circuits attached to main battery. There is also an explosion risk due to fuel fumes or hydrogen build-up if the compartment has been closed.
6) Never leave an external charger connected and unpowered. Many chargers do not have a blocking diode and will discharge batteries.
copyright © by Ken Cook 1996, all rights reserved
Reprinted by permission of "Bass & Walleye Boats"