Battery regulator for solar power system

Although newer types of solar cell have come to the fore recently, amorphous cells are bound to be with us for some time to come, mainly because of their low cost. Most solar cells based on amorphous technology have a relatively high internal resistance, which results in large differences between the loaded and 'open-circuit' output voltages. Where a rechargeable battery is used as an energy storage device, a voltage regulator circuit is in order that charges the battery when the cell output voltage is high, and forms a minimum load on the battery when the cell output voltage is low.