During 20-plus years as a professional contractor, I've acquired more materials than my shop could hold. I solved the storage problem with a 20- x 60-ft. outbuilding, but lighting it presented a challenge. Running electricity to the building would have required digging a 150-ft. trench through very rocky, root-infested soil. Instead, I opted for a solar-powered direct-current (DC) lighting system — a relatively easy-to-install, economical solution.
If you want to light up a storage building, gardening shed, child's playhouse or any other structure that's not close to a conventional power source, this type of system may be the answer. The individual components are relatively inexpensive, and if you're comfortable with basic wiring, you should be able to install them yourself.
If you've never worked with solar-powered DC electrical components, first consult an electrician and an electrical inspector; then talk with a reputable supplier before making any purchases. (I consulted with and bought my components from Batterystuff.com — see SOURCES in PDF below.) The supplier will ask questions about how you'll use your system and how many lights you want to power and then recommend components that will do the job.
For most solar-powered DC systems, you'll need to purchase a deep-cycle 12-volt battery (available at automotive or marine parts suppliers) and a battery maintenance charger kit. I chose the Battery-Minder SCC015, which includes a 15-watt solar panel, a maintenance charger and a battery-condition indicator.
In DC lighting systems, the deep-cycle battery provides the working power to the light bulbs. The solar panel recharges the battery, the maintenance charger monitors the condition of the battery and adjusts the incoming power from the solar panel accordingly, and the battery-condition indicator lets you know if the battery is no longer charging properly.
You'll also need to purchase 12-volt DC light bulbs, which are available through a variety of on- line retailers. (I purchased mine from Buylighting.com.) Although you could use standard household 110-volt AC bulbs, that would require the purchase of a power inverter, and according to the support staff at Batterystuff.com, using an inverter would result in a 20 percent power drop from battery to bulb.
Installation and wiring
Installing the individual components is a pretty straightforward process. In a spot that gets plenty of sunlight, mount the solar pan- el black-side-up with an air space between it and the roof. (Panels often come with mounting brackets, but depending on your installation, you may have to fabricate your own brackets from strips of galvanized metal.) Run the supply line from the solar panel to the inside of the building; then install the battery, with the maintenance charger and the battery indicator mounted nearby.
The solar panel should be mounted to an area of the roof that receives as much sunlight as possible, and there must be an air gap between the roof and the panel.
When it comes to running electrical cable for the system, make sure you use cable that's rated for the amperage your system will draw. You can determine the number of amps with a mathematical formula: watts 4 volts = amps. Standard 14-gauge sheathed electrical cable is rated for 15 amps; 12-gauge is rated for 20 amps. I installed four 50-watt, 12-volt DC bulbs per circuit, which equates to 16.66 amps, so I needed to use 12-gauge sheathed cable. As an additional safety measure, install an inline 12-volt fuse for each circuit you run.
Inline fuses protect each of the lighting zones in the event of a short or an overload.
Once you're finished, call your electrical inspector to have him or her sign off on the installation. Then throw the switch and enjoy the free light.