Hi, this is Wayne again with a topic “Solar Power Tools”.
Solar power is a great way to get electricity out to a remote project site. One way to do this is to use a solar panel to charge the batteries of your cordless power tools. All you need is a solar panel and a simple charge controller. Before we start, i should point out that there’s always a certain amount of risk when using a diy battery charger, so use caution and be careful to never overcharge the batteries. The first thing that you need to do is take note of the connections on your battery. Two of the connections will be the positive and negative terminals. Any additional terminals may be for a temperature sensor or a thermal fuse. You can identify the positive and negative terminals by checking to see which ones connect to the power tool, then use a multimeter to determine which one is positive and which one is negative label these for future reference. The next thing that you need to do is select an appropriate solar panel for safety. We want a panel that will charge the battery more slowly than the regular charger.
The easiest way to do this is to get a panel that has a lower wattage rating than the charger. The panel also needs to have an open circuit voltage, that’s higher than the voltage of the battery when it’s fully charged so fully charge your battery and check its voltage then compare that to the open circuit voltage of the panel. In this example, i had a 12 volt battery, its charger runs at 3 watts and when fully charged the battery measures 14.4 volts.
So i wanted a panel that was rated for less than 3 watts and had an open circuit voltage that was greater than 14.4 volts. Now you need a charge controller. I decided to build one using a 555 timer ic.
Here’S the overall circuit the circuit is powered by the panel through a 5 volt voltage regulator. The battery is connected to 2 voltage dividers and the output of these is sent to pins 2 and 6 on the chip. When the battery reaches a certain voltage, the timer activates the relay and disconnects the battery from the panel to prevent overcharging when the battery is removed or partially discharged the system resets itself, the operating range of the charger is set by the values of the resistor. These values work for a 12 volt battery, but you can easily change the resistors to match your battery. First, i prototyped the circuit on a breadboard. Then i soldered the components onto a printed circuit board. I trimmed the sides of the board with a dremel so that it would easily fit in a small project enclosure. The easiest way to test the system is to switch the battery in the solar panel. The battery is connected to the input of the charger and supplies a stable power source for the circuit. The solar panel is connected to the output of the charger and acts as a variable voltage.
Source start by covering up the solar panel. Then slowly uncover it as more light hits the panel the output voltage will go up when the voltage reaches 14.4 volts. You should hear a click from the relay activating then slowly cover up the panel again and when the voltage drops below 13 volts, you should hear another click from the relay. Turning off now just switch the battery and the panel back to their original connections and you’re done this system lets you charge your batteries anywhere. That has sunlight thanks for watching and check back next week for more diy hacks and how to’s .