I live on 10 acres which backs up to a 7 acre pond. I fish in the pond using my small 12 foot row boat which I leave there all year round. A few years ago I built a platform dock for easier access to the boat. I can drive most of the way to the dock but the final 200 yards is swampy and wet. Up until now, when ever I decide to go fishing I needed to carry, oars, tackle boxes, electric trolling motor and a 75 pound motor battery that final distance. A big inconvenience!
So I built a small storage shed near the dock using mostly scrap material. To the roof, I attached a small solar panel to keep the battery charged.
I purchased a 10W solar panel and charge controller on Amazon. When I received them, I connected the controller and panel and measured the output. It was about 20V with no load, 13.3V with a load. Then I connected the battery and it seemed to be charging. I had to add some lengths of wire and change the small aligator clips to large ones.
Docooler 10A 12V/24V Solar Charge Controller
Solar Panel Battery Regulator Safe Protection
ECO-WORTHY 10 Watts 12 Volts Epoxy Solar Panel Module
12V Battery Charger Camping
The battery I have has appoximately 100 amp hours of capacity. On our recent fishing expeditions, I noted we rarely used 20% of the charge with regular use of the trolling motor. So to estimate time needed to charge from 80 to 100%.
10W Solar Panel => Power / Voltage = Amps => 10W / 12V = 0.83A
Amp hours needed for charge:
20% X 100 Amp Hours = 20 Amp hours
Time required = 20 Amp hours / 0.83 A = 24 hours
But I only estimate the panel is at full efficiency for about 6 hours in the summer due to the angle of the sun so that means it should take about 4 days to recharge the battery after a typical use. Perfect for weekend fishing excursions.
I drew a sketch of the shed and decided that it needed to be small and tall. It was built on a 3 foot square base with 2X6 framing and a plywood floor, on 3 foot 4X4 posts burried 2 feet in the ground. One wall is 7 feet tall, the opposite wall is 6 feet tall, giving the roof a slope. I had to purchase about a dozen 2x4s for framing, but the sides and roof are made from left over pole barn steel panels.
Most of the framing was constructed in my garage then carried to the site in a pick up truck. The post holes for the base flooded with water, but some dry redi-mix concrete was poured in and some old 4X4 posts were laid under the base framing incase it starts to sink. The buried posts are really so vandals can't tip over the shed. The steel was attached with a combination of left over pole barn screws and nails.
I put the hinge screws beneath the sheet metal panels so they could not easily be removed. I also put on a hasp for a combination paddle lock.
I had to build a wooden frame for the solar panel since it is just an epoxy covered FR4 fiberglass sheet, similar to circuit board material. The panel slid into slots I cut with a table saw. I hung it on the sloping roof with some metal clips in a Southeastern facing direction.
So far things seem to be as expected, but the trolling motor has not seen heavy use yet. In hind sight, I wish I would have purchased a larger solar panel maybe 30 or 40 watts. It will take quite a few days to charge the battery to full if it is ever needed. Also a charge controller that displayed battery charge in % would have been nice. But this project was meant to be done on the cheap side so what I have is adequate.
Larry Rankin from Oklahoma on August 07, 2017:
Super cool project!