Friday, 23 September 2016

DIY - Solar Phone Charging Unit

This article explains about how to make your own solar based mobile phone charging unit. The design is very simple and completing this should not take you more than 2 hours.

List of components required:
      1.       Solar panel : 3W,6V panel
      2.       Sealed Maintenance free lead acid battery: 6V,4.5AH
      3.       Diode: IN4001
      4.       DC -DC Step Down Buck Converter KIS3R33S Module 7V- 24V to 5V /3A
      5.       USB based mobile charging cable( Normal data cables will not work)
      6.       Connecting wires
      7.       Soldering kit

Circuit connections diagram:

Working principle:

Mobile phones have inbuilt batteries and they need to be charged every few days or every day depending on how often the mobile is used. Batteries can be charged only with Direct current whereas the electricity we get in our normal household sockets is Alternating current. A mobile phone charger does the job of converting AC to DC and keeping the output voltage and current levels suitable for mobile charging. Chargers typically have efficiencies ranging from 60-90% depending on the quality (This is why some of the chargers get heated up quickly)

On the other hand solar panels convert solar energy to DC electricity. With suitable circuitry we can store this DC electricity in an external battery and charge the mobile phone when ever required.

The selection of solar panel and battery depends on various parameters like number of mobiles to be charged and the voltage levels of the battery etc. We have used a 6V, 4.5AH battery which can charge a typical smart phone once every day.  A 3W 6V solar panel is chosen since that is enough to charge the external battery in 7-8 hrs. The solar panel is directly connected to the battery with a diode in between to avoid reverse flow of current from the battery to the solar panel when there isn’t enough sunshine and during night time.

A DC-DC converter module is used to convert 6V battery voltage to 5V output since mobile batteries are very sensitive to charging voltage and current( a normal car battery regulator can be used but the efficiency is very low)

            As shown in the circuit diagram, connect the positive end of the solar panel to the positive end of the diode (silver ring on the diode represents negative) and the negative end of the diode to the positive of the battery. The negative end of the solar panel can be directly connected to the negative terminal of the battery.

·         Solder the terminals and use insulation tape to make sure shorting of terminals doesn’t happen.

·         Identify the input side of the DC-DC converter and connect positive and negative of the battery to the positive and negative of the DC-DC converter input respectively.

·         The output of the DC-DC converter is a USB port where the charging cable is inserted. (Note: Normal data cables do not work so a simple charging only cable should be used)
·         If the connections are proper, you should be able to see a red light glow on the DC-DC board and your mobile phone should display charging.

·         We had used a voltage and current measuring device called a charger doctor at the output to verify if the voltage and current levels are in the suitable range. This unit is not required.

Try this fun project and let us know your experience or queries in the comments section below.

Where to buy?

4.       Diode IN4001,connecting wires, soldering kit and charging cable : Any regular electronics store

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