I'm new to electronics and have been looking into building a solar cell charger for NiMH batteries. I got hold of a pair of small solar panels rated at 5v open circuit voltage, and 100mA short circuit current. I confirmed this under bright sunlight with a multimeter. Each panel will easily exceed these values if the sun is bright enough. I connected one of them to a pair of AA NiMH batteries in series, thinking that perhaps I could trickle charge them under the sun. But there was hardly any current flowing into the batteries. So I added another panel in series with the first, as in the diagram below. http://myhabitat.net/t/naive-charger-circuit.png This time, a current of about 100mA flowed into the batteries. The voltage across the solar panels was at 2.6V. I left my 'charger' out in the sun for a few hours. Then I disconnected the solar panels, and discharged the batteries through a load of 50R while making occasional measurements of the voltage across the battery terminals. In short, the batteries started at 2.46V. After 5 hours they were down to 2.37V. Does this mean that this charger circuit actually works? I thought that even a simple charger that just delivers a steady trickle charge would need some kind of extra circuitry in there somewhere.