How to Make a Simple Solar Powered Li-Ion Battery Charger
A solar photovoltaic panel can be used to charge almost any kind of electrical storage battery. A lithium-ion (Li-ion) battery is the type used in many cameras, cell phones, laptop computers, and other portable devices. Li-ion batteries are sensitive to overcharging and require sophisticated electronics in the charging device to ensure the batteries are charged correctly. Making the battery charger itself is not recommended, but connecting a Li-ion battery charger to a solar panel is relatively easy.
Go to a store that sells cameras and computers, or go on the Internet. You will find many chargers available for the Li-ion battery you want to charge. Buy a charger that has a car cigarette lighter connector, and that can run on a direct-current (DC) voltage of up to 24 volts.
Read the specifications for the charger. Note the maximum charging current in amps. For a laptop computer battery charger, the charging current may be 5 or 6 amps. For camera and cell phone batteries the current will usually be less than 1 amp.
Check the output of the solar panel. Look for the maximum power current (Imp) in amps, and the maximum power voltage (Vmp) in volts produced by the panel. Confirm that the maximum power current produced by the panel is equal to, or more than, the maximum charging current required by the battery charger. Check that the maximum power voltage is between 12 and 24 volts.
Buy an adapter that will connect the solar panel to the cigarette lighter plug. These adapters have two alligator clips at one end (red and black) and a female type lighter connector at the other end.
Install the solar panel in a place where no shadows cross the panel during the day. Orient the panel due south and inclined at an angle equal to the latitude of your location. Connect copper wire to the positive and negative terminals of the panel, and run the wires down to the alligator clips of the charger adapter. Connect the positive wire to the red clip, and the negative wire to the black clip. Plug in the Li-ion battery charger and check that it is working.