Solar Electric Charge Controller and
Portable Power Supply

This projects is a device that will allow a solar panel to efficiently recharge a DC battery. The solar panel is operated at an optimal power level regardless of the battery voltage. The controller will vary the voltage across the panel
to find and maintain the maximum power point. the battery is charged using using pulse width modulation techniques. The major components of the projects are:
-a boost DC-DC converter
-a microcontroller
-a current sensing microchip
-a Liquid Crystal Display for data output
-a serial computer interface(for programming and data collection)

Project Design
the solar panel which provides power, the rechargeable batteries which receive power, the circuitry to maximize the power transfer between the two, and a LCD and two LEDs as outputs to the user. a DC-DC converter, a Microchip PIC18F452, and a computer serial port interface to program the microprocessor and receive data output on a terminal program forms the circuitry part.
The Microchip PIC18F452 is programmed using the PCW C Compiler. This microcontroller reads the solar panel voltage,
solar panel current, and battery pack voltage through analog to digital converters. Resistors are used to regulate the voltages between 0-5 volts to be read by the PICâ„¢s ADC. the solar panel current is measured by MAXIM 471. The program takes the ADC readings to monitor the solar panel power output (voltage * current) and it is used to find the operating point where this power is maximized. the battery pack voltage is also read to implement three-stage battery charging. The ADC is also used to output values to the LCD.
The DC-DC converter converts the input voltage from the solar panel to the battery voltage. Pulse-width modulation (PWM) from the microcontroller controls the duty cycle of the transistor.

for full details, refer this pdf
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