End of April, first week of May 2017
We have been spending much more time on the hook, anchor or mooring, than I had expected this soon. We've been on a mooring at Marathon for two months now: it's cheap, we have more privacy and the air flow is better. When we are at a marina we have the world's largest extension cord to give us (almost) everything we have come to expect power wise on shore, but when away from the dock, and not traveling most days, electrical power use and generation is a daily issue.
The previous owner had these 75 watt solar panels that butterfly off the rails on either side of the cockpit. Not the best place for them, and we had tried to tear them off during several unplanned docking maneuvers, but until we get an arch about the best we can do location wise. Talking with Jason the diesel mechanic while getting our engine in shape inspired me to take the plunge, buy some new panels and reduce our dependence on running the generator, which was running over two hours some days.
The controller for the old panels was a good one and actually could handle about 360 watts. Back when the old panels were bought I would guess that they were $6-8 per watt, so well over a grand for two light bulbs worth. In perusing Ebay under Jason's direction I found two 160 watt panels for just over $300, less than a buck a watt, that were slightly wider and longer but would still fit in the same spot with some modifications. A little more than half the difference in power was from increased area, but much of it was from increased efficiency achieved over the years.
I was annoyed to find that the brackets that hold the panels to the rails and allow them to rotate were more than the solar panels, and we should be doing the arch within a year or so, which meant this was a temporary fix. I needed about a six inch extension for the 2" wide, 1/4" thick aluminum bars that hold the panels. Bar this big was not in stock on the island, and I could only find 1" wide bar about 30 miles away, so I spliced that on with 1/8" bar, relocating the pivot points to keep the panels just above the deck when vertical. I'm not the handiest guy, and a drill press really would have been nice, but the splices are definitely stronger than the panel. That takes care of the mechanical installation, which just leaves electrical.
The electrical pass through connectors linking the panels on the outside of the boat to the controller on the inside are in many ways weak links. When the panels are banging there should be over 8 amps passing thru each one, which is a lot for something that also needs to be weather and waterproof. I reluctantly went with the same design as was already there even though I had damaged one connector by stepping on it accidentally during one of the previously mentioned unplanned docking maneuvers.
The side I had stepped on was fine electrically, and I was able to figure out which pins did what and reproduce that with the new connectors, but the other side was a mystery because nothing indicated which pin did what. I finally just took the whole thing apart and found a big ball of corrosion on the back of the boatside half of the connector. In all likelihood that panel was delivering no power at all, which (partially) explains why my power usage estimates never worked.
With both sides now generating more than twice as much power we are within 10-20 amp hours of our daily electrical needs from the new panels on a sunny day. Instead of running the generator for a couple hours a day, we can run it for an hour every three days or so. We need to do this anyway for a few minutes to make hot water, so this dramatically reduces the urgency of watching every watt.
Jason reviewed my installation and had another suggestion. Since the connectors are always a weak link, he bolted and bonded/sealed two sections of brass threaded rod thru the hull. Rings on the ends of the positive and negative wires are installed onto these, inside and outside the boat. Simple and bulletproof for low voltage (<17 volts). I bought the brass threaded rod and nuts, but that project is for another day.