How To Recharge Batteries With Just A Playing Card And The Sun

Rechargeable batteries save money and reduce hazardous waste. IF you remember to charge them, that is. Reaching for a battery only to find out it needs to spend 4 hours in the charger is a real bummer.

Frustrated by this problem, Instructables user Shawn Frayne decided to invent a battery charger that works anywhere there’s sunlight–no outlet required.

“I wanted a cheap and fast way to make battery chargers that I can keep on my desk, so that I could have an armada of charged batteries at all times,” Frayne writes. (Don’t we all?)

“I didn’t want to take up more outlets and have more wire spaghetti with plug-in chargers, so I settled on a solar charger.” Smart man.

Step 1: Gather Your Materials

A roll of Copper tape with adhesive backing (available at most electronic component stores)

Super glue (the thin stuff, also known as cyanoacrylate)

Playing cards

4 NdFeB magnets between 1/4″ – 1/2″ diameter, 1/32″  – 1/8″ thick, any grade N42 – N52 (available lots of places, including www.kjmagnetics.com)

4-8 small pieces of raw lasercut PV silicon cells (aka “solettes”)

Several AA rechargeable batteries

“This project works best with NiMH AA and AAA batteries, but can also work with NiCads (which are not the most environmentally benign battery in the world, so best to avoid buying these if you don’t own them already),” Frayne points out.

Step 2: Fold the Playing Card and Apply Copper Tape

Bend the short edges of the card over so that it looks like two-legged table.

Then add a couple pieces of copper tape. Make sure to wrap the copper around the entire width of each flap. These will be the “wires” that connect the energy generated by the solar cells to your AA battery (via the magnets).

Step 3: Attach 2 Magnets to the Underside of the Card

The magnets are the terminals that connect your solar charger to an AA battery. You can also add a magnet to each side of the card (for a total of four), and they’ll hold themselves in place without glue.

“When the magnets grab onto a AA battery, current can flow through the copper tape, through/on the surface of the magnets, and then into the AA battery,” writes Fayne.

Step 4: Place the Solar Panels

In order to generate enough power, the solettes must be stacked in series with a shingling technique. This is where your superglue comes in.

“The (+) output is the grey underbelly of the first solette in your shingled fan-stack. The (-) output…can be accessed either at the bus bar or white silver ink runners on the blue top surface of the final solette in your stack,” Frayne explains.

(More about this in the video at the end)

Step 5: Coat the Top Layer of the Card with Epoxy

Mix up some 5-minute, two part epoxy. Then, pour it onto the top of your the card charger, covering the solettes and magnets.

Do NOT get any epoxy on the inside magnets, since it will prevent them from carrying current to your battery.

Frayne recommends putting your new charger on some popsicle sticks so that the epoxy can drip off the sides of the card.

Step 6: Wait five minutes for the epoxy to dry and…voila! You’ve got a AA battery charger that’s powered by the sun.

Meet Frayne (his mustache is awesome) and learn more about how the project works in this video.

Project and images courtesy of Instructables user sfrayne.

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