Solar Powered Battery Charger...
Separate Loads
This project commenced with the purchase of what I've come to refer to as the primary solar panel. I came across an online auction offering a deal I couldn't refuse. The selection of all other components of the solar powered webcam revolved around this panel. But I didn't anticipate incorporating a ventilation system into the assembly when the primary panel was chosen. Since the ventialtion system was an after thought, so too was the secondary solar panel. I didn't want the camera battery to have to bear the load of the ventilation fan. The solution was to introduce a second solar power system into the assembly strictly dedicated to powering the fan. This would spare the battery power for use in powering only the camera system.▼
Primary Panel
When I purchased the main solar panel I had essentially dived head first into this project. I had a whim to assemble a solar powered webcam but the solar panel purchase was based mostly on price with little regard for just how much power I would ultimately require to recharge the battery. Fortunately, the panel suited my needs very well. It is a 16 volt polycrystalline solar panel that produces up to 24 watts of power (depending on available sunlight). Polycrystalline type solar cells are relatively efficient at converting sunlight into electricity. It was manufactured by Kyocera and this particular model is fitted with a sturdy aluminum frame which includes mounting flanges. One of the few modifications I made to the panel was to apply silicone caulking around the perimeter of the surface glass to add some extra weather resistance to it. It came with what appears to be weather stripping in place but it seemed worn and I couldn't bear to lose the panel to a short circuit caused by water infiltration. I also had to drill 4 holes in the frame: 1 for the lid support, 1 to pass the wires through, and 2 for the piano hinge.▼▲
Primary Hardware
The flanges at the back or the primary solar panel frame turn under the panel at the back. I took advantage of the resulting surface by drilling a hole and using it to mount a 1-1/2" corner brace aligned to be flush with the outside edge of the frame. The corner brace has a hole in each of its two ends and I used the remaining hole to attach a lid support to. I could have simply drilled the hole into the outside faced of the frame flange but making the hole on the underside of the frame instead of on its outer edge minimized the chances of rain water finding its way onto the more vulnerable underside of the solar panel. The panel underside is sealed with only a waxy padded paper like material. The lid support allows the solar panel angle of inclination to be manually adjusted to match the inclination of the sun at different times of the year. The placement of the hole for the corner brace was strategically selected to maximize the range of movement of the lid support. The hinge used to attach the solar panel to the support frame also facilitates adjustment of the panel's angle. A piano hinge was used in lieu of two separate leaf type hinges because it would result in a sturdier assembly and because it was also easier to align than two separate hinges would have been. Opening up a hole in the center of the panel's bottom flange allows the wires to pass from the underside to the front side while staying tucked up tight against the panel where it's protected from rain water. This also reduces the difference in distance between the wire connection to the solar panel and the wire connection to the electronics enclosure as the panel angle changes. Thus the wires didn't have to be cut excessively long to compensate.▼▲
Secondary Panel
The idea for including a secondary solar panel was born from the idea to include a ventilation system into the assembly. The ventilation system would have been too taxing on the battery I wanted to use so I isolated the fan load from the camera battery. Again I came across an online auction with an offer I couldn't pass up, this time for ventilation fans. Click over to the ventilation page to read more about the fan I'm using. My search for an inexpensive 12 volt solar panel to power the fan by led me to automotive battery trickle chargers. The charger's plastic enclosure didn't fit into my plans for mounting the secondary solar panel so its low price made canibalizing the charger less scary. The output amperage of these chargers is rated at 120 milliamps which is a near perfect match for the ventilation fan which consumes up to 170 milliamps. One characteristic about these panels worth noting is that they're made with amorphous type solar cells. Although less expensive than polycrystalline type cells they are also less efficient. But more important is the fact that they're very sensitive to the amount of light they're exposed to! This type of solar cell must see bright, unshaded sunlight or they won't work. A momentary cloud passing in front of the sun or a shadow from a nearby tree will cause this panel to stop generating electricity. What this means is that the ventilation fan will not run at night or when the panel is shaded. But these are the very same conditions under which the primary solar panel is likely not charging the battery either. If the battery is not charging it's not producing by-product gases either and there really isn't any need to ventilate the enclosure. So the sensitivity of the amorphous type solar panel works in our favor by effectively shutting off the ventilation fan while little or no battery charging is occuring.▼▲
Secondary Hardware
Once exposed the charger's solar panel is really nothing more than a piece of glass about as thick as window glass. The wire leads from the back of the panel are attached with solder, but the solder doesn't adhere well to the glass so the wire connection is very flimsy. Handle with great care! This fragile panel assembly was strengthened by clamping it to a rigid backing made from aluminum plate. Mirror holders were used to clamp the panel to the aluminum plate. A hole had to be drilled in the plate aligned with the location of the panel's wire leads since the leads protrude further out than the back of the glass. Otherwise the wire leads would act as a pivot point and would prevent the panel from lying flat against the backing plate. Because their connection to the back of the solar panel is so fragile, a splice plate was used to pinch the wires against the underside of the aluminum plate and prevent them from accidentally being pulled loose. A 1-1/2" corner brace was used to connect a lid support to the aluminum plate. And similar to how the primary solar panel was mounted, a highly customized leaf hinge was used to attach the aluminum backing plate to the solar panel support frame. The combination of the lid support and the leaf hinge allow the solar panel's angle of inclination to be manually adjusted to face the changing height of the sun at different times of the year. Lastly I applied a bead of silicone caulking around the perimeter of the glass solar panel to resist rain water trying to find its way between the panel and the aluminum plate where the wires are exposed and where a short circuit could occur.▲
