Power bank made at home with 20800 mAh, how to make a power bank creative

Utilize an old mobile battery of 3.7 volts and a rechargeable cell of 1.2 volts to produce a key-size power bank. As we are aware, in order to charge any mobile device, 5 volts are required. These two components will produce 4.9 volts, which is sufficient to charge any mobile device.
Consequently, we present a key-sized power bank that can charge any mobile device at any location.

Step 1: MATERIALS REQUIRED
1 Old Mobile Battery (3.7V)
1 AA Rechargeable cell (1.2V)
Connector
Wire
Switch (micro-slide switch)
Lots of tape

Step 2: MAKING
Attach a mobile battery to the rechargeable cell with the help of tape. Now we have to attach the wire from '+' terminal of rechargeable cell to the '-' terminal of mobile battery.
Attach the separate wire '+' terminal of mobile to the side terminal of the switch. And then take the other wire and attach it from the middle terminal of the switch. ( it will be positive line of power bank)Now we will take the separate wire which will be attach from '-' terminal of rechargeable cell. ( it will be negative line of power bank)

Step 3: FINALLY YOU CAN CHARGE YOUR MOBILE
Take the connector which will consist of two line - red line ('+' line) & other line ('-' line).Now, the positive line of power bank made earlier will be attach with the connector carrying positive line & negative line of power bank with the negative line of connector.

Step 4: FINAL STEP
Cover the whole material with the tape. You can cover your power bank with any type of box ( plastic or cardboard) to make it more attractive .
This device can charge anything which charges with 5V.