Designed by Knut Karlsen, the SunCats are basically a set of old NiMH rechargeable batteries wrapped in a flexible Photo Voltaic cell created by the Institute for Energy Technology. When the batteries are drained, you simply leave them sitting in a windowsill or anywhere with ample sunlight and they'll recharge themselves. The PV cells were simply glued onto the batteries and wired up using a conductive silver pen and some flat wires scavenged from a broken canon lens. At the moment they only provide a weak trickle charge to the batteries, but Knut envisions a second version with built-in capacitors and electronics to make the charging process more efficient.