How to Get Light From Your Backup Battery
Unless you're hooked on the romance of flickering candles during a power outage, you may want to add a light source to your solar-charged backup battery. Here's how you can do it quickly, easily and on the cheap. No need to reserve it for blackouts, either -- it makes a fine camping accessory.
Apr 4, 2013 5:00 AM PT
Over the last few months, we've been building out a solar generator. The project started as a simple, heavy-duty battery with a cigarette lighter adapter -- inspired in part by images of Hurricane Sandy victims scrambling to find methods for charging devices like smartphones and tablets.
We then added a photovoltaic solar panel with charge controller to the project to extend battery life. The panel collects energy from the sun's rays and tops up the battery, providing theoretically endless power for charging phones.
Let There Be Light
The third part of our project is to add light. New, super-efficient Light Emitting Diode, or LED, technology means it's possible to create bright light with very little electrical draw.
This technology is a perfect solution in the event of an extended power outage -- or a camping trip.
Step 1: Source Your Lights
Look for LED technology designed by leader Cree, and made or licensed by the company. I've written about ipso-facto-standard Cree before in High-Tech Flashlights Could Turn You Into a Collector.
Look for a low amperage draw -- a couple of amps is perfect. Take advantage of vehicle applications, which are already in 12-volts DC, the correct voltage, rather than patio flood lights -- an alternative -- which need converting.
I used an off-road work light designed for All Terrain Vehicles made by AGT (about US$62 for a pair at Amazon). Each light uses nine 3-watt Cree chips creating a bright 1200 lumens each.
Importantly, one light draws an incredibly low two-amps. So, if you're using the 55-amp hour Optima battery suggested in the first part of this How To series, one AGT light will run for 13.75 hours before the battery becomes 50 percent depleted and will need a sunlight shot from the solar panel and charge controller combo.
Step 2: Mounting
Mount a light-included stainless steel bracket onto a polyethylene battery box by drilling an appropriate hole in the box lid and fastening with light-included bolt. You can pick up a battery box, sometimes called storage case, at auto parts sellers.
The boxes are also often used in trolling applications for fishing, so marinas are a good source too.
Then attach one of the lights to the bracket. Keep the other light as a spare.
Step 3: Prepping the Charge Controller
Remove the existing fuse from the existing red wire that runs between the charge controller terminal labeled "Battery +" (or similar) and the battery.Remove the existing cigarette lighter adapter from the terminals labeled "Load +" and "Load --" on the charge controller, and put the adapter to one side.
Step 4: Gather the Parts
Obtain an in-line automotive pigtailed fuse holder, a 10-amp fuse, some butt connectors and ring terminals. Fry's Electronics is a good source of parts.
Tip: You can read about wire and the tools to use in Coming to Grips with Wire.
Step 5: Crimping Connections
Crimp one red ring terminal onto the included black lead that's connected to the LED light's housing. This is the negative side.
Crimp one end of the new empty fuse holder's red pigtail to the included red lead that is also connected to the LED light's housing. Use a blue butt connector. Then crimp a red ring terminal to the other end of the fuse holder's red pigtail. This creates in in-line fuse in the red, positive side of the light. Don't add the fuse yet.
Step 6: Wiring
Attach the red wire that leads from the LED light, via the fuse holder, to the positive terminal labeled "Load +" or similar on the existing charge controller.
Connect the black wire to the negative terminal labeled "Load --" on the charge controller.
Step 7: Turn on the Light
Insert the load circuit fuse and then the battery circuit fuse. The light will illuminate.
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