Components (estimated prices include shipping):
Solar Battery Panel 13 W Briefcase style – ebay ($85)
Solar Battery Controller – DC voltage controller from allelectronics.com part # SOL4UCN2 ($33) 12V 18A sealed lead battery – batterymart.com part #SLA-12V18 ($40)
Plastic box (you probably have one of these at home unused or can find one at Staples or Target)
2 x Cigarette adapters – these are adapters that plug into your car’s cigarette lighter and usually have one or two female sockets on the ends ($16)
Wire ($2)
Mono 1/4″ phono plug – allelectronics.com #SPH ($1)
(optional) DC/AC Inverter 400W – Walmart #PI-400W ($34)
(optional) pair 1W 12V DC LED bulbs – ebay ($13) and two flood lamps with clamp ($13) and 1 extension cord with male pins substituted with 1/4″ phono plug as above ($3)
The solar panel is rated at 13W. If you intend to only power very small appliances such as game boys, mp3 players, cell phones, etc, you can use a smaller, lower wattage panel and smaller battery and save about $35.
Instructions: When you first receive the battery, I suggest you slow charge it using a standard auto battery charge, if available. This may help to extend the total life of the battery.
The solar panel comes with different options for supplying power – either alligator clips or an automobile style cigarette socket. I prefer the female socket, as the battery and controller will be housed securely in a transportable plastic box. You will need to purchase a small, 12V cigarette adapter with wire leads. Cut the wires near the female socket (assuming you will use the male socket to attach to the solar panel). Strip the wires and attach each to the correct poles of the voltage controller. The male end can then be used to connect to the solar panel. In my model, I drilled a hole into the plastic box to let the male socket extend outside the box. While you’re at it, you might as well drill a few extra holes on the sides just under the lid for ventilation. Also, if you have pets or young children, it is a good idea to lock the box as a precaution.
Use a good gauge wire to connect the battery to the voltage controller. I recommend using alligator clips on the battery terminals, as these are easily removed when the battery terminals are connected to other devices (such as an inverter).
Place the panels in direct sunlight (generally facing South or you can point it at the sun and reposition it throughout the day if you wish) and you should be charging your battery. The system is not designed to be water proof, so place it in the sun when you expect several sunny days in a row and bring it inside if you expect rain or heavy fog.
At sufficient charge, you will see the light above the resistor diagram on the controller illuminate. This means the battery is sufficient to power other small 3V, 6V, or 12V devices from the output plugs on the top of the controller box. Again, I have used a modified cigarette adapter, with one female end and the other stripped wire to attach to a male, mono 1/4″ plug (again, you should watch the polarity). The mono plug is inserted into the 12V connection at the top of the voltage controller.
Uses:
I can charge cell phone batteries or whatever device can be connected to a cigarette lighter that doesn’t draw more than 4 amps DC. If you try to draw more power, the fuse will blow. See Sears’s 12-V appliances for examples of what you can do with a 12V power supply. Many smaller portable electronics items may have 12V cigarette adapters as an optional accessory.
When I want AC power, such as for small home appliances, I detach the alligator clips on the battery and replace them with alligator clipped wires from the inverter (see inverter instructions). When the inverter is in place, the system basically operates as a low wattage AC power source. This means you can power many household devices that use less than 400W. Most of these inverters offer two standard AC plugs. If you are unclear how to calculate wattage requirements, you can look at the appliance itself, which will normally show watts consumed. This systems uses a battery rated at 200 Watt-hr, which means you can power a 60W bulb for about 3 hours (assume a little power loss from dc to ac conversion), or a 13W florescent bulb for 10-14 hours.
The best application I have found is to power 1W DC LED lamps – MAKE SURE THESE ARE DC DESIGNED BULBS and THE WIRING YOU USE IS DEVOTED TO THIS DC APPLICATION ONLY. With a single day’s charge, I can light two 1W LED flood lamps for about 60-70 hours non-stop. This is plenty for a week or two’s worth of reading outside on a warm summer night. You can certainly wire additional bulbs for more lighting simultaneously.
The second best application I have found is for our electric hair trimmer, which my wife kindly uses to cut my hair. We save $20 on average per haircut or about $175 – $250 per year. If you include power costs (actually very minor in this example), transportation cost, and time, it’s certainly worth more like $300-$350 per year. Over ten years, you’re looking at $4000 with compounded interest. Wouldn’t $4000 make a nice gift or vacation for two?!!!
Conclusions:
This solar setup requires direct sunlight. The voltage controller, while some feel is not necessary for such a small system, is designed to charge the battery only when there is sufficient voltage being generated by the panel. In other words, it’s designed to keep the current flowing in the right direction when it’s sunny and stop current flow when clouds block the sunlight or it is getting dark. Winter seasons, clouds and latitude will affect the number of direct sunlight hours available per day.
I am also asked how long it would take to recoup the investment expense. Besides the above variation in sunlight exposure, your utility rates may be higher or lower depending on where you live. Of course, besides energy input variables, the lifetime of the battery and value will depend on what you use the battery for. From what I understand, draining a lead battery up to 50% and recharging is fine, but draining it 90-100% routinely will shorten the life of the battery. Despite this, I am expecting my system to return its investment in about 2 – 3 years.
Other factors factors in favor of building this system are:
1. it makes you keenly aware of the energy required for normal household appliances, so you may find yourself turning off lights more frequently or using more powerful appliances for shorter periods.
2. the energy you generate is “free”.
3. if the energy companies increase rates, at least you don’t have to pay higher rates for this solar power.
4. if your home is subject to frequent blackouts, this is a nice backup system that does not require gasoline.
5. if you go camping and still want lights or to work on your computer briefly, you can pack this in your auto trunk.
6. if you take my advise and read a book for a few evenings a week outside, you’ll save plenty on electricity you may otherwise have spent on television.
7. after you finish this project, you may be inclined to share it with your friends, who may wish to give this a try or maybe even take on an entire solar home remodeling project! the next thing you know, solar power will end up charging a battery in a vehicle, thereby reducing our dependence on foreign oil and overall carbon emissions. now, wouldn’t that be a good thing?!!!
DISCLAIMER: The above instructions should be used as a guide. If you are unfamiliar with electronics, soldering, or do not know how to measure current or direction of current flow, seek professional assistance before starting to build a solar battery charger.
