Posts tagged green energy

How to make a small solar generator

solar generator

Here’s my set up for a small solar generator.

Another green projects for all you DIY folks. Harness the power of the sun and live off the grid. Okay, so this particular unit won’t let you off the grid, but it can charge all of your rechargeables, cell phones, mp3 players, some CFL lights and much more. All using solar energy.

What you need:

  • 5 watt or greater Solar Panel (I used 2 of these solar panels) But keep in mind any more than 10 watts total would require a solar regulator
  • Fuse and fuse holder (I have used a 5 amp fuse allowing me to use up to 60 watts (5 amps x 12 volts) before it blows, which is consistent with the wiring gauges I used to construct my set up. Please ensure you use a proper fuse for your application and design)
  • Volt meter (optional) (I used one from radioshack which I put in a simple plastic case. This helps to monitor state of charge but isn’t necessary.You can also test with a multimeter.)
  • 18 amp hour 12v sealed lead acid (SLA) battery or similar deep cycle battery
  • 12v cigarette adapter outlet (this lets you plug in all your car adapters directly to your solar generator)
  • Power inverter (optional) (This will allow you to convert your 12v DC battery juice into 120v AC for lamps or other applications)

Construction can be as simple or complex as you want. Basic wiring would have the fuse placed as close as possible to the positive battery terminal. You would then connect the solar panel: solar positive to fuse to battery positive, solar negative to battery negative. And connect your cigarette outlet negative to negative, positive to fuse to battery positive. An optional power inverter can also be connected to battery. Particularly, if you opt to plug into your cigarette adapter, please ensure all wire gauges are appropriate for the power you are drawing. Your specific set up and application will dictate the proper fuse and wire gauges to use. You typically want to the lowest fuse rating that allows you to operate what you want to operate, within the safe range for your wiring.

How to use:

Place the solar panel in a sunny spot ( I have mine propped up against a window) and it charges pretty well., Direct sunlight will recharge the battery more quickly.

If you have attached a cigarette outlet, plug in any car adapters you have to charge cell phones, mp3 players, and much more.

If you have attached a power inverter, flip the switch on your inverter, and plug in as you would a wall socket. (Be aware that some devices are not compatible with non-sinusoidal power inverters – Consult the manual for your specific power inverter for details)

For an added bonus, you can also pick up a Duracell NIMH Mobile Charger and harness free solar power to recharge all your NiMH batteries for your digital camera, remote control, etc.

Solar AA Battery Charger


AA battery solar charger

Harness the power of the sun to power all of your battery-powered devices. In this simple example, I constructed a solar AA battery charger suitable for use with NiCd batteries.

From various internet sources, I read up on the proper ways to charge NiCd batteries. I decided for this initial example to use only NiCd because they are readily available, cheap and typically accidental overcharging simply reduces the batteries lifespan, rather than creating a fire hazard as with a lithium ion. According to several sites, the safe “slow charge” method is to charge the battery with 1/10th of its capacity for 10-12 hours as so-called “overnight” charger do. These charges require the user to keep track of when they began the charge and remove the charger at the appropriate time as they do not incorporate any sophisticated ways to test the charge status.

The AA batteries I purchased are rated at 600mAh, so the slow charging method would require roughly 10-12 hours at 60mA. Using some broken solar cells I purchased online, I connected together 5 pieces, in series. Each piece produced roughly 80mA in direct sunlight and roughly .5 volts each (smaller pieces produced less amperage). Connected in series, this produced roughly 2.5 volts at 80mA max (in my tests, indirect sunlight through my window produced roughly 50-70mA – perfectly suited to charging the AA battery.

The voltage was also ideal at 2.5v as to create a voltage differential to ensure energy flowed into the battery (1.2v) even after the voltage drop from the diode. The diode serves one important function in this set up and prevents the batery from discharging during lowlight conditions by ensuring energy only flows into the battery and not back out through the solar cells. The entire assembly is mounted to an old CD-R as a sturdy re-claimed backing. Mounting the battery clip to the bottom provides enough angle to point the solar cells out the window.

While the efficiency of charging only one AA battery in this charger is not ideal, it is an excellent proof of concept and I have tested its ability to fully charge a NiCD AA battery in one sunnny day many times with succeess. For a larger scale, more useful solar device, check out the small solar generator I created next.

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