" If we were going to determine what was broken in the radios, we needed a power source. With no electricity, this meant batteries. [...] we'd walk to the trading center and look for used cells that had been tossed in the waste bins. [...]

First we'd test the battery to see if any juice was left in it. We'd attach two wires to the positive and negative ends and connect them to a torch bulb. The brighter the bulb, the stronger the battery. Next we'd flatten the Shake Shake carton and roll it into a tube, then stack the batteries inside, making sure the positives and negatives faced in the same direction. Then we'd run wires from each end of the stack to the positive and negative heads inside the radio, where the batteries normally go. Together, this stack of dead batteries usually contained enough juice to power a radio. "

― William Kamkwamba , The Boy Who Harnessed the Wind: Creating Currents of Electricity and Hope