Solar lights are actually quite simple in theory. They have 5 key parts.
The solar panel
This gathers the energy that powers the light. Solar panels are actually a collection of photovoltaic cells. A photovoltaic cell is a device that converts sunlight to energy. When light hits the cell, the light creates electrical energy. To make sure that your solar lights are working to their full efficiency, you need to place the cell somewhere that it can gather enough sunlight. Don’t be afraid to experiment to get your lights working just right.
The battery
Once electricity is produced, it is used to recharge the battery in your solar light. The battery is usually a nickel-cadmium battery for peak performance, and is called a ‘deep cycle battery’. This means that it is designed for frequent charging and use without a loss of performance. The battery is charged during the day and at night it runs to power the light! Most solar lights are designed to last for the whole night when fully charged.
The light sensor
A small photocell detects the light level in your garden, and when it is dark enough it switches on your lights. You may find that solar lights activate a bit before dusk if you place them in a shaded part of your garden.
The light
Most solar lights use LED technology as their bulb. Light Emitting Diodes are a great option because they use much less power than normal light bulbs and they last for much longer. Most solar post lights are actually sealed to protect from the weather, so the bulbs are difficult to replace.
The housing
The housing is where solar lights can be very different in design. The only important function is to protect the light from the weather and other damage, and to hold all the parts together. Other than that, the housing can be as decorative as neccessary for each style of light!