9V battery charger for phone

This workshop will show you how to get 5 V for USB from a 9 V battery and use it to charge your mobile phone.

In the photo, the assembled circuit is in work, but this is not the final option, since I will also make a case for it at the end.

So, let's get down to manufacturing.


The picture shows the components necessary for assembling the charger, including one empty case from the old battery, in which the device will be built.

Components and materials:

  • Old battery for the case.

  • USB port

  • Integrated circuit regulator 7805.

  • One green LED.

  • 220R Resistors - 3 pcs.

  • Solder.

  • Wires.


The diagram shows the pinout of the 7805 controller, the USB connector, and the actual circuit of a simple converter.

Charger assembly according to the scheme

After disassembling the old battery, parts can be soldered to the base with the connector. Everything gathers in five minutes, and I think that nothing needs explanation, except for the resistors connected in the middle USB contacts - Data + and Data-. And they are needed so that the cell phone itself understands that it is connected to a charger, and not to a computer for data transfer.

The circuit does not need settings and starts working immediately.

The LED indicates the presence of a flow of charging current. If it does not light, it means the battery is completely discharged, or the phone is fully charged.

Transformer Ready

The picture shows the finished device in the case. It is convenient to carry the mini-charger with you in your pocket, since it is very small, and together with the battery.

Original article in English