Mobile Phones, are an essential commodity. There are often times when we find ourselves in situations when the battery is about to go off, leaving us in emergency. People generally keep mobile powerbanks or car chargers with themselves but they are also only useful upto an extent.

In this instructable, I decided to make a mini USB mobile charger that can be used to charge a cell phone just with a 9v battery. So next time you find yourself in a tough situation, just buy a 9v battery at the corner shop and you will have enough power to handle the emergency situations.

Note: This charger will only work for android devices. It is recommended to use a high current 9v battery (like Duracell or energiser), a normal cheap chinese battery will not provide enough backup.

Step 1: Watch the Video

A video is a wonderful tool that provides deep insight into the understanding of the procedure and also makes it easy to follow the steps.

Step 2: Order Parts

Ebay.com

7805 Voltage regulator - https://rover.ebay.com/rover/1/711-53200-19255-0/...
Female USB Port - https://rover.ebay.com/rover/1/711-53200-19255-0/...
100 ohm resistor - https://rover.ebay.com/rover/1/711-53200-19255-0/1...
LED - https://rover.ebay.com/rover/1/711-53200-19255-0/1...
9v Battery - https://rover.ebay.com/rover/1/711-53200-19255-0/1...
Soldering Iron - https://rover.ebay.com/rover/1/711-53200-19255-0/1...
Hot Glue Gun - https://rover.ebay.com/rover/1/711-53200-19255-0/...

Amazon.com

7805 Voltage regulator - http://amzn.to/2q8oRU8
Female USB Port - http://amzn.to/2q8hOej
100 ohm resistor - http://amzn.to/2seVmBm
LED - http://amzn.to/2xBS2a5
9v Battery - http://amzn.to/2txOMJL
Soldering Iron - http://amzn.to/2r3IX6g
Hot Glue Gun - https://amzn.to/2Sf7oad

Amazon.in

7805 Voltage regulator - http://amzn.to/2qLukTZ
Female USB Port - https://amzn.to/2BSasUl
100 ohm resistor - http://amzn.to/2sB1W4m
LED - http://amzn.to/2yhvKtT
9v Battery - http://amzn.to/2ulSibD
Soldering Iron - http://amzn.to/2qC47qG
Hot Glue Gun - http://amzn.to/2rjNE9r

From Home & Local Store: Two bottle caps, old 9v battery, spray paint and connecting wires.

Step 3: Let's Begin

Take two plastic bottle caps.
Cut a slit at the center of the cap such that a female USB port can be inserted in it.
Make a hole at the center of the other bottle cap.
Using a spray paint, color the bottle caps as per the desired choice.
Solder wires to the Pin 1(Vcc) and Pin 4(Gnd) of the USB port.
Insert the USB port in the bottle cap as shown in the image above and secure it with hot glue.
Take a 3mm LED and solder a 100 ohm resistor to '+ve' LED leg.

Step 4: Add the Components

Take a 7805 voltage regulator IC.Solder the Vcc wire from the USB port to the output terminal (Pin 3) of the 7805 IC.
Similarly, solder the Gnd wire to the Gnd terminal (Pin 2) of 7805 IC.
Make a hole on the side of a bottle cap.
Insert the LED in the hole and secure it with the Hot Glue.
It is an indicator LED that will indicate the power to the circuit.
Connect the '-ve' LED leg to the Gnd terminal of 7805 IC.
Connect the other leg to the input terminal (Pin 1) of 7805 IC.
Take a 9v battery connector clip and paste it over the surface of the second bottle cap. Note: You can easily extract a connector from an old 9v battery by watching this Video.
Connect the '+ve' battery terminal to the input terminal (Pin 1) of 7805 IC.
Connect the -ve battery terminal to the Gnd terminal of the 7805 IC.
Make sure to refer to the schematic diagram attached above.
After verifying all the connections, seal both the bottle caps together using hot glue.

Step 5: Testing the Charger

Our mini Portable USB charger is now ready. Connect a 9v battery to the charger. Plug a USB cable in the USB port and connect it to the mobile phone.

The mobile device begins to charge and the backup will depend on the quality of 9v battery used. A good quality battery can charge a 3000mAh cell phone battery upto 15-20%.

Note: This device can also be used to charge the cell phone using any wall adapter upto 12v in case of emergency situations. Because of 7805 voltage regulator it will provide regulated 5v to the cell phone. However, you can also add capacitors to the input-Gnd and output-Gnd terminals of 7805 to get smooth voltage output.

So friends, this here concludes the instructable, stay tuned and SUBSCRIBE to receive regular updates. In case you might have missed, have a look at the video and see how i made this mini USB charger at home.

I have also made a hand powered emergency charger, which is also quite useful. Have a look at the instructable here or watch the video below.