Changing battery chemistry is another option. But why stop there? 900 milliampere-hour batteries are made that still fit in an AA cell socket. We could replace it with a 300 milliampere-hour battery and get twice the energy storage capacity. Our little solar light came with a tiny 1.2 volt nickel cadmium battery that can store 150 milliampere-hours of charge. Solar garden lights are often sold in sets, making this easy.Īnother simple improvement is to replace the cheap battery with one that can store more energy. If you can't find a larger solar cell, you can put two or several of the same size solar cells in parallel with one another, to get twice or several times the energy. This will provide more current to charge the battery, which will allow us to place the garden light where it might not get enough sun otherwise. One obvious improvement is to replace the solar cell with a larger one. Now we have enough information to improve our solar garden light. 47 microHenrys will give us 50 milliamperes, which would be suitable for three or four LEDs. 100 will give us 28 mA, which is more than we normally want in an LED, but probably won't hurt it too much. 270 microHenrys will give us 10 milliamperes. This is fine for a single LED, but if we want to drive several LEDs, we can reduce the size of the inductor and get more current. 330 microHenrys will allow 8 milliamperes to go into the LED. We can control how much current goes to the LED by choosing different values for the inductor. It detects when the solar cell is in the dark, and starts up the circuit inside that boosts the 1.2 volts from the battery to over 3 volts, and sends that to the LED. It charges the 1.2 volt battery during the day, using power from the 2.5 volt solar cell. The integrated circuit does several things. These come at a rate so fast our eyes see it as continuous light.Ībove is the schematic for the Solar Garden Light, using the 5252F integrated circuit and a 330 microHenry inductor. The answer is a clever circuit that uses a steady 1.2 volt source, and produces a series of spikes of higher voltage. Inside a solar garden light, we find a single 1.2 volt battery.

Blue and white light emitting diodes need more than 2 volts to run.

It seems to work with red lights, but not with blue or white. Try connecting a solar cell that produces 2 volts to a light emitting diode.

Volt solar lights