Here’s a simple circuit which you can use to charge any device that uses a USB charger. (Smartphones, Tablets, Portable music players, etc.)

## Step 1: Get the Components

• Soldering board (1)
• Voltage regulator 7805A (1)
• 9 volt battery (1)
• Battery snap (1)
• Solid wire - White/Black colour (2 cm)
• Solid wire- Red color (2 cm)
• Female USB connector – Type A

## Step 2: Tools Required

• Soldering iron
• Wire cutter

## Step 3: Put It Together

Assemble and solder the components as shown in the diagram.

## Step 4: How It Works

The 9 volt battery is connected to the battery snap.

Such batteries cannot be used to charge any device directly (because the device will blow), so an IC is used to reduce the voltage to 5 volts.

The power now goes to the USB connector, from where any USB charger cord can be plugged in.

## Step 5: The Finished Model

<p>Most smart phone batteries are 1500-3300mah.</p><p> A 9V battery has 50-400mah and at 500mw load has less than 300mah capacity.</p><p>You're also losing 20% of that 300mah thru the circuit as heat.</p><p>Just exactly HOW much does this remaining 240mah charge your phone ???</p><p>Ref : <a href="http://www.powerstream.com/9V-Alkaline-tests.htm" rel="nofollow"> http://www.powerstream.com/9V-Alkaline-tests.htm</a></p>
9v to 5v there's a lot of wasted energy. Why not go with 4 AAA (6v) to 5v ?
<p>Ideally you need between 2.0 to 2.5V above the regulator due to the regulator voltage drop, so you should have at least a 7V power source when using a 7805 regulator. Having said that a 9V transistor battery as a power source isn't a good idea either as they have very high internal resistance and they can typically only provide 200mA to 300mA constant current draw. A 9V transistor battery can work but not for very long.</p>
More like 1.6V to 2V. You still need 5 1.5 volt batteries either way. Or a lower dropout regulator than the 7805.
I would highly recommend to use the two capacitors showed in the data sheet for the voltage regulator, without it the regulator might start to oscillate and damage the equipment connected to it. :)
<p>Thanks for the suggestion.</p>