Introduction: How to Make a Portable Charger

About: Just another person curious for nature and its governing laws! Always have my own particular ways of building, designing, and performing on things! Exploring science and technology !

Smartphone has become an integral part of life. One of the most versatile products in the market. One can have access to internet, music, multimedia, gaming and so much more! But it really annoys when battery drops down while chatting or talking to your bae or maybe clients! So why be slave to this power constraint? Why not make your own portable charger at relatively competitive price to that available in the market! Although it can't outmatch the tech that other power banks provide but it serves its purpose. At the end there is a great satisfaction in making things by self. So let's get started!

Step 1: Getting Started

Now let us understand what are we going to do:

  • We shall build a circuit that connects external battery to the device (smartphones etc).
  • This circuit is made using lm2576(5v) voltage regulator IC some capacitors and an inductor.
  • The battery may be li-po battery, li-ion battery (rechargeable) or any non rechargeable battery available in the market.(note: the output voltage of the battery must be always greater than 5 volts.) I would strongly recommend you to purchase rechargeable battery(trust me tried with non rechargeable ones, not efficient).

Key features:

  • Quite simple and customizable
  • Really inexpensive
  • Power anywhere, anytime.
  • Can be made by anyone without having any much knowledge in electronics (provided they follow the circuit diagrams correctly!)

Step 2: Material Requirement

  1. Rechargable Battery
  2. Lm2576 IC (5V)
  3. 100 micro henry Inductor
  4. 100 micro farad capacitor, 1000 micro farad capacitor
  5. 1n5822 Diode
  6. USB female (A type).
  7. Circuit board
  8. Screw terminals
  9. Switch

Step 3: Understanding the Lm2576 Circuit(Step Can Be Skipped If Wanted To)

Lm2576 IC comes of various types (5v, 12v, 15v, and adjustable type). For this project we need lm2576 5V type.

  • The pin configurations along with their description is provided in the figure.
  • The pin descriptions may be a little bit difficult to digest but after having a look at the circuit diagram it is pretty easy to understand.
  • Lm2576 here acts as a voltage regulator which steps down the unregulated DC supply (given by the battery) to pure DC constant supply at 5V.
  • This output at 5V will be used to charge your smartphones.

Step 4: Still Learning Lm2576...(Step Can Be Skipped If Wanted To)

  • The Cin is used to keep the input supply stable. At least 100 micro farad capacitor(polarized) needs to be used.You may use capacitor which has more capacitance value.
  • Pin 3 is connected to ground. Pin 5 depicted as ON/OFF must be grounded. It means when this pin is grounded lm2576 is in the ON state and shall function as voltage regulator.(note: Please don't keep the pin 5 floating).
  • The Cout is used for filtering the output voltage. A 1000 micro farad polarized capacitor is appropriate.
  • Now during the discharge of these capacitors we need to protect the lm2576 circuit hence diode D1 is used.
  • Make the connections as shown and make sure that the capacitors are soldered in vicinity of lm2576.
  • The input side of the circuit will be connected to the battery.
  • The output side of the circuit will be connected to your smartphone charging wire.Here we shall use a USB female port so that you can easily attach and detach the charging wire.

Step 5: Circuit Assembly

  • Add a screw terminal so that you can take your rechargeable battery out in case of charging.
  • Also add a switch in the circuit for greater control.
  • At the end, add a female USB port.
  • USB female terminals need to be soldered with utmost care because one wrong connection may damage your mobile's battery.
  • But if connected correctly no need to worry!
  • USB female has 4 terminals named 1,2,3 and 4.
    1. 1 stands for "Vcc".
    2. 2 stands for "data -".
    3. 3 stands for "data +".
    4. 4 stands for " ground".
  • So connect positive part of output to terminal 1 and ground to terminal 4. Leave the terminals 2 and 3 as it is.
  • Please make USB connections perfectly as explained. Before testing the circuit onto your smartphone have it tested on a small led for its proper functioning and connections.
  • This is the final circuit diagram. If you can't understand lm2576 circuit and still want to make portable charger just assemble the circuit as shown perfectly and whola power!

Step 6: My Board !!

My Board looks like as shown in the figure. I am not good at arranging and soldering stuffs. The diode has been soldered below the circuit board hence not visible.I did not have 1000 micro farad capacitor so I used two 490 micro farad and one 100 micro farad capacitor in parallel so that net capacitance becomes 1080 micro farad(Quite witty and resourceful, right?). Also I have shown a small demonstration video at the end.

So finally you can have power at your fingertips! You can keep this portable charger in your bag and carry power anywhere!