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?)
Step 1: Gather Your Materials
Super glue (the thin stuff, also known as cyanoacrylate)
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
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
“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
“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
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.