The purpose of the project is to build a simple charge controller for solar and wind systems based on IC NE555 Timer. Michael Davis, the designer, decides to use IC 555 instead of MCU because he worried that the microcontrollers would be too expensive or difficult to obtain in some parts of the world, and too difficult for non-technical people to program. The project works on 12 Volt systems but it can also be used for 24 Volt systems. The change that you need to do is replace the relay with one rated for 24V coil voltage, and re-calibrated the pots for new high and low set points for the higher battery voltage.
The controller can be used to handle multiple solar panels and/or wind turbines. All power sources connected in parallel and fed into the single input connection. Each individual solar panel or wind turbine needs to have its own blocking diode though. Here is a diagram of a typical system with a wind turbine and two solar panels feeding the charge controller. Typically an AC inverter is included in the system to power AC loads. Download : solar wind system controller schematic diagram.