Rechargeable Batteries with Solar Cells

Project by Knut Karlsen



Prototypes

At home i always have some batteries lying around, either rechargeable or normal ones. Usually they are empty, but i'd like them to be always fully charged. I could use a normal charger and there is a lot of solar devices that charge rechargeable batteries. I wanted it simpler; why hasn't anyone made a battery with integrated solar cells? The idea of the "SunCat" batteries where born. The batteries should just bask in the sun like a cat and left for a while, in a sunny window, they would slowly recharge.During my research for my diploma i was in touch with scientists at IFE that experimented with the production of flexible solar cells. They where kind enough to send me some samples in the right dimensions that i could use for the prototypes (full set at flickr ):I had some older NiMH rechargeable batteries that i glued the flexible Photo Voltaic (PV) cells onto. The PV cells are rated at 1.8V and the batteries are 1.5V so they match quite well.Half glued you can see the really shiny polymer substrate backside of the PV cell. The crude written text says: 3x0,6V B: 13.411.09 Which i guess is the voltage and a batch number.Using a conductive silver pen and some flat wires from a broken canon lens I made an ok connection to the PV cell.This setup is infact a (quite weak) trickle charge r. It is not ideal, but really convenient. A second version would have some electronics (to check when full) and capacitors to charge the batteries more efficiently, but the battery would then be smaller if it all needs to fit within a C-cell battery.The sun did not shine today, infact it was snowing. But i'll sure let them hang around in my window and take some more pictures when the sun shines.