A powerbank is a portable device that can supply power from its built-in batteries through a USB port. They usually recharge with USB power supply. ... Due to its general purpose, power banks are also gaining popularity as a branding and promotional tool.

Portable Power Banks are comprised of a special battery in a special case with a special circuit to control power flow. They allow you to store electrical energy (deposit it in the bank) and then later use it to charge up a mobile device (withdraw it from the bank). Power Banks have become increasingly popular as the battery life of our beloved phones, tablets and portable media players is outstripped by the amount of time we spend using them each day. By keeping a battery backup close by, you can top-up your device(s) while far from a wall outlet.

The Power Banks we're talking about are good for almost any USB-charged devices. Cameras, GoPros, Portable speakers, GPS systems, MP3 players, smartphones and even some tablets can be charged from a Power Bank - practically anything that charges from USB at home can be charged from a Power Bank - you just have to remember to keep your Power Bank charged, too! Power Banks may also be known as Power Stations or Battery Banks, too.

Step 1: Materials and Hardware Required

Transistor LM7805
Battery Snap
Battery
Ice Cream Sticks
USB Cable
Wire Cutter
Screw Driver

Software Used -

Arduino

Step 2: Building Our Own Pocket Sized Power Bank

Step 1: Take a 7805 IC (5V Voltage regulator), there are three terminals. Input terminal, output terminal and ground. Take a USB female connector, it has four wires they are red, black, green and white. Cut down the green and white wires. Peal off the insulation of red(+ve) and black(-ve) wires.

Step 2: Connect the output port of the 7805 IC to the positive terminal of USB female connector. And the ground terminal of the 7805 IC to the negative terminal of the USB female connector.

Now, connect the input terminal of the 7805 IC to the positive terminal of the 9 volts battery. And the negative of the 9 volts battery should be connected to the ground of IC 7805.

Refer to the circuit diagram above to connect the terminals correctly.

Step 3: Testing

After all the connections, test your circuit by a multi-meter or just connect a device to the USB female connector to charge. It works! I tested it with some other smartphones too, it worked. It doesn’t work for an iOS devices, I used an iPod and it did work. There are some other requirements for a power bank to work for an iOS device.