Always a bit on the curious side … This project started with a visit to the local electronics supply store … Waiting in line and seeing some 15 watt Coleman solar panels on sale. It was a long line … and well … I bought one … and a battery, a small DC to AC inverter, some connectors and a solar charge controller … and apparently … a new project!
Back at my third floor apartment I put the solar panel in my bedroom’s south facing window, read the instructions and had my fish tank’s water circulating pump and heater running off the rig in no time.
I do not think it made it through the night!
I disconnected the pump and heater and waited.
Almost a week later the charge controller said the battery was charged again. (It was a very small battery).
Another trip to the store, a second solar panel … and then a third … this was getting more expensive that I had “planned”.
I plugged just the water pump back in and waited!
The system made it through the rest of the winter, but as the sun started to climb higher in the sky and the leaves on the tree across the street started to sprout the system started to fail, went into hibernation is probably a better description of what happened.
But in any case … The fish were back on the grid!
Fast forward a couple of years … The low winter sun seemed to be the key to keeping the fish happy, though the system seemed to be getting tired. A single cloudy day would shut things down.
Adding a second bigger battery helped … but I had run out of south facing windows,
Meanwhile … back at my “day job” as the owner of a small sound company I had a dilemma. My longest running client’s annual Town Day event was growing, adding another stage in the middle of the town common. With no electrical outlets handy the somewhat uncomfortable solution was to run 100′ of extension cord to one of the outlets they used to power the holiday tree lights. Add hundreds of attendees, some pony rides, a Kids Olympics and a dog show and uncomfortable was starting to be an understatement.
Moving the electronic gear closer to the outlet and using wireless microphones to get to the performers did help, but it was less than ideal and … I was curious.
Later that year I had the chance to fill in as an engineer for a friend at what was supposed to be a wonderful evening concert on a hill top in Vermont. The weather that day was threatening and the concert was wisely moved into an old barn on the property.
While waiting for the “go/ no go” on the outdoor site we checked out the hill top location and saw what was to be the power for the event. A small trailer with a solar panel, not much bigger than all three of my 15 watt panels put together, some batteries and some sort of inverter. The folks from Yestermorrow had donated the trailer’s use for the concert and I seemed to be the only person worried about it … after all, It was my sound system that was going to be plugged into it!
The trailer was used for off grid construction projects. It would be set up at the site, the panel pointed at the sun with the trailer left alone for the week to soak up the sun and charge the batteries.
A construction crew would show up on the weekend with their skill saws, drills and other power tools and build something!
I never saw it in action … But it got me thinking …
A close inspection of my gear showed me the wattage each piece used. Some mathematics some coffee and a trip to the local marine supply store and it looked like I would be able to run everything for the three hour event off of two deep cycle marine batteries.
I bought three just to be on the safe side!
I explained the idea to my contact at Town Day and he gave me the go ahead to try it with the understanding that I would still bring the extension cord … Just in case.
I set everything up early that day and went off to set up the other stages. I left a note explaining that I would be back at 1:00 to pack everything up and gave them my cell number if they should have any questions.
Apparently a couple of things had been added to the schedule and they would be needing the sound system until about 4:00!
Oh well … I told them I would be by around 1:00 with the power cord but that they should use the battery power anyway.
When I arrived at 1:00 everything was going nicely. I checked the inverter’s built in power meter and it showed that the batteries were still in the same 90-100% full range they had started the day with.
The system ran until a little after 4:00, a total of 7 hours with the inverter’s meter still showing the batteries in the 90-100% range at the end of the day!
The initial voltage off the batteries was 12.8 volts … The ending voltage was 12.3 volts.
I had purchased two 120 watt solar panels and a new charge controller to recharge the batteries after the show.
I brought the batteries up to my father’s house, set the them up on his back yard patio and plugged the two panels into the charge controller.
Four days later the batteries reached a high of 13.7 volts … The first two days rained most of the time … The second two were mixed sun and clouds.
I was very excited and happy, but more than a little confused.
It was time for the learning to begin … And there was lots to learn!