To charge the 6-volt NiCd battery in this little device uses a miniature 3-volt solar battery. Battery, in turn, can charge many models of cellular phones and other portable devices.
The circuit converts solar energy into a pulse current charging the battery for a drip. Loading the solar battery, the inverter maintains the output at its potential level of about 1.5 V. efficiency schemes, equal to 70% at a current of 100 mA solar cell drops to 30% while reducing the current to 25 mA. This is not a high efficiency, but the simplicity and low cost circuit as well as the absence of the exotic elements justifies its use in this device.
This scheme is designed to charge the battery from a source with a lower voltage. Do not use it to charge the battery with the same or lower voltage than the solar panel generates. For proper operation of the scheme necessarily requires the battery. Various models of mobile phones have different requirements to the charge, and perhaps this device will not work with all phones, without exception.
Parts list : R1 : 1.5 kOhm R2 : 3.9 kOhm R3 : 10 kOhm R4 : 180 Ohm R5 : 4.7kOm R6 : Thermistor 10 ohm PTC PC1 : 3-volt solar battery from the battery lamp Landscape C1 : 22 uF electrolytic capacitor 16 C2 : Ceramic capacitor ceramic 100 pF C3 : 10 uF electrolytic capacitor 16 L1 : 50-300 uH choke D1 : Schottky diode 1N5818 Q1 : Transistor 2N4403 , or equivalent Q2 : Transistor 2N4401 , or equivalent J1 : Output connector B1 : Nickel-cadmium battery, 6 V with fuse