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Systems:  Electrical System

Batteries and Battery Cables

I began the electrical system by installing two Attwood group 27-size plastic storage boxes in the engine room, on the after end of the platform that also supported the fuel tank.  Installing the boxes was a snap:  screw a pair of supplied brackets (per box) to the platform, and run the supplied nylon strap through.

With the boxes installed, I continued by lugging two new Group 27 batteries up on deck and into the boxes.  I planned a very simple electrical system, with the two batteries simply wired in parallel and no complex measures for starting battery isolation and so forth.  Since the mission of the boat is so basic, and there will be little call for electrical power on board other than for basic lighting and engine starting, I saw no reason to complicate things.

Next, I determined the general location of my interior electrical panel, which would also house a basic on-off battery switch.  With that location figured out, I could begin running the battery cables.

I needed four cables running between the engine room and the interior of the boat (to the panel area):  positive and negative distribution, power from the switch to the starter motor, and the main ground.  I began with the two longest cables, which ran from the panel to the engine ground and starter motor.  I used #2 battery cable in red and yellow.

I began by drilling a 2" hole through the bulkhead between the engine room and the cabin, up beneath the sidedeck and inside one of the settee lockers (starboard side).  I lined the hole with a short length of white hose that I held in place with cable ties on each side of the bulkhead; this provided chafe protection where the cables and wires would run through the bulkhead.

Then, I ran the cables through, pulling lots of extra.  Once I had the cables run roughly to their ultimate connection points on the engine (ground to the forwardmost engine mount bracket, and the power to the starter motor), I stripped the cable ends and installed tinned copper lugs, which I then covered with heavy-duty adhesive-lined heat shrink tubing.

Connecting the new terminals temporarily to the studs as required, I then worked my way backwards into the cabin, securing each cable along the way with cushion clamps as required.  The square corners required for a neat installation consumed lots of cable, more than expected (of course).  Eventually, the cable was well secured in the engine room and up to the bulkhead pass-through, and inside the boat I determined the final length of the cables and cut the ends; then, I installed more tinned lugs of the appropriate size (3/8" hole for the positive cable connection at the battery switch, 5/16" for the negative cable to the negative distribution bus).  This seemingly basic process took a couple hours to complete, and by then the day was over.

I continued the next morning by fabricating the two remaining main battery cables:  the cable running between the battery and the negative distribution buss, located behind the eventual panel location; and the main positive battery cable.  I had just enough cable remaining on the reels to complete these jobs.

I chose some solder terminal connections for the battery ends.  The terminals were designed for use with pre-sized solder pellets, sold according to the cable size.  I was using #2AWG cable, so chose the green pellets.  The process was simple: 

First, clamp the terminal in a vise, and drop in the pellet.  Then, heat the terminal with a torch until the solder melts, and stick in the cable end.  To prepare the cable for this step, I first stripped off about 3/4" of the insulation (the instructions called for 1", but this was too much), and then applied some liquid flux (part of the system) to the exposed wires.  When the solder was melted, I pushed the cable end into the liquid, completing the installation.  Finally, I covered the terminal and cable end with more of the heavy-duty heat shrink tubing.

With the soldered connections complete, I ran the bitter ends of the cables through the engine room and into the main wiring area behind the starboard after settee, securing them with cushion clamps as I went.  Then, inside the cabin, I determined the cables' final lengths and installed the appropriate crimped tinned copper battery lug terminals.

I secured the cable running tot he negative distribution buss, but left the remaining cables loose for now until I was ready to install them in their appropriate locations, to be determined once I managed to build the panel and finalize some other connections.

I built two jumper cables required to connect the two batteries in parallel, and installed them between the two batteries.  Then, I moved on to the final connections behind the main distribution panel in the cabin, securing the battery cables to the battery switch, distribution panel, and negative distribution buss as required.

I also added a 100-amp main fuse in the system as a safeguard.  Located between the battery switch and the electrical panel, this fuse would serve as a catastrophic protection device for massive current flows, should any circumstances arise that might create such a scenario.

As before, I labeled all the cable ends and protected each connection with heavy adhesive-lined heat shrink tubing, and secured the cables as required with rubber cushion clamps.
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