- on Power Supplies
- Published in issue 7/2004 on page 0
Solar-Powered High Efficiency Charger
This is a simple NiCd battery charger powered by solar cells. A solar cell panel or an array of solar cells can charge a battery at more than 80 % efficiency provided the available voltage exceeds the ‘fully charged’ battery voltage by the drop across one diode, which is simply inserted between the solar cell array and the battery. Adding a step-down regulator enables a solar cell array to charge battery packs with various terminal voltages at optimum rates and with efficiencies approaching those of the regulator itself. However, the IC must then operate in an unorthodox fashion (a.k.a. ‘Elektor mode’) regulating the flow of charge current in such a way that the solar array output voltage remains near the level required for peak power transfer.