Portable mobile charger using 9V battery

In the previous post, I showed you how to make a portable powerbank using Li-ion battery.
Now in this post, we will use a 9v battery to make an emergency portable powerbank/mobile charger.

Components required:- 

1. 7805 IC 
2. 10uF capacitors x2
3. Resistance 220ohm
4. LED 
5. Connection wires and PCB.

CIRCUIT SCHEMATIC:-

Connections:- 

1. Connect the +ve of the 9v battery to the input pin of the 7805 IC. 

2. Connect the -ve of the 9v battery to the Ground pin of 7805 IC and to the micro USB out port.
3. Connect the +ve out of the 7805 IC to the +ve pin of the micro USB out.
4. Connect a LED in series with a resistance in parallel to the +VE out of 7805 IC and GND.(Check the above image).

Click here if you don't know how to use 7805 IC


Working:- 

The 7805 IC is a linear voltage regulator so the input current is same as the output current.
The Output voltage is about 5V ( 4.8-5.2V). 
Therefore, the  Output Power = V x I = 5 x I ( here,"I" is  the input current).

When the supply is connected to the circuit the 7805 IC steps down the voltage to 5V which is suitable for charging the mobile.

The efficiency n= (Output power)/(Input power) x 100,
So the input voltage is 9V and current is same as output current,
5/9 x 100 = 55%, So the efficiency is about 55%.


Precautions:- 

1. Do not connect the 9V supply directly to the Micro USB port or to the mobile

2. 7805 IC specs:
Input voltage = 7-35V
Output voltage = 5V 


Note- The above circuit is used to charge a mobile so the current draw will be much higher, which will overheat the 7805 IC and cause damage to it. To prevent this from happening place a heatsink over the 7805 IC.

Heat generated = ( Input voltage - 5) x Current