In a previous article, we already talked about how to make a USB charger on a solar battery. However, that design has one significant drawback: charging can only be done during daylight hours. What if you need to call, and the mobile phone is dead and already dark? To get out of this situation, the author decided to improve the charger.
Materials needed to create this model of a solar powered charger:
1) a solar panel with a voltage of 4-5V
2) holder for finger batteries in the amount of 2 pcs.
3) Schottky diode
4) socket for the connector from the power supply
5) a wire with a connector from the power supply
6) a metal box from candies as a device case
7) hot glue
8) step-up voltage converter up to 5 V
9) electrical tape
10) soldering iron
Let us consider in more detail the main points of the design of a solar charger.
Before starting work, it is necessary to select the materials for the charger qualitatively. Batteries must be selected based on the following factor: the charging current should be about 10% of the capacity of the battery itself. Thus, if we take a 3000 mAh battery, then the current generated by the solar panel that will power this battery should not exceed 300 mA. At the same time, the author does not recommend the use of less powerful solar cells or batteries, since with a small current supply it will take quite a long time to charge your phone.
Also, to build this device, you will need a step-up USB voltage converter. As its name implies, it is needed to increase the voltage from 0.5 V to 5 V, which are necessary to power a mobile phone. Such converters are quite cheap, especially if they are ordered as an author through online stores.
The principle of operation of such a charger is quite simple. During the day, the solar panel charges the batteries, and when the mobile device is connected, it is charged from the batteries and the solar cell. In the dark, when the solar battery does not generate energy, the phone is fully charged by the batteries.
For a better understanding of the work, the following is a diagram of the design of this USB charger for a solar-powered phone:
First of all, the author decided to prepare a solar battery for use in this device. To do this, he soldered the wires to the solar panel. Moreover, since the solar panel itself is larger in size than the housing under electronic part of the charger and batteries, the author decided to make this solar panel removable. A wire was used from the power supply with the corresponding connector so that the solar panel could be easily disconnected during transportation, and in order to prevent the wire from being damaged or torn off during operation, it was decided to fill it with hot glue.
Further, the author began work on the body of the product. For the connector of the solar battery and USB output, two technological holes were made on a can of candy, which will serve as the body of the filling of the charger.
Then, a blocking diode was soldered, which is needed so that the batteries do not discharge through the solar battery and save stored energy.
Further, according to the device diagram, wires were connected to the converter and the battery holder.
Since the housing used for the device is made of metal, which conducts electricity well, the author installed a dielectric at the installation site of the converter. In this case, the usual insulating tape served as a dielectric.
Further, the entire structure together with the batteries is placed inside the device.
If the case has sufficient dimensions, then it is possible to improve the power of the charger by installing another holder for the batteries in it. moreover, the batteries must be connected in parallel. As a result of such a modernization, the author received a battery capacity of 6000 mAh and a voltage of 2.4 V. The author also plans to increase the power of the solar battery for faster and more complete battery charging.
But even if it happens that the batteries are discharged at the wrong time. for example, at night, when it will not be possible to charge them from the solar battery, you can still charge the phone using this device. To do this, it is enough to get the discharged batteries and replace them with ordinary finger batteries and already with their help charge your gadget.