For the cell phone to charge, charger output must be above 4V and can deliver a maximum current of 500mA. This charger circuit will step up the voltage from 1.5V to 5V DC to reach the cell phone charging requirement. The circuit uses only an AA or AAA 1.5v battery (1V to 2.4V). The charger is composed of simple oscillator, a rectifier, and voltage regulator. This is similar to the Joule Thief circuit.
The feedback winding F is composed 5 turns of #30 AWG magnetic wire and main winding P is composed of 6 turns of #24 AWG wire. The 5.1V zener diode and 2200uF capacitor regulates the output voltage to ensure proper charging.
The windings are not critical, you can experiment using different number of turns. If ever the charger doesn’t have any output, try to reverse the winding connection.
My opinion is that this can charge the cellphone battery only for short period of time because the 1.5 volt battery power capacity is much lower than the phone’s battery.
This article was received from Subham Chatterjee. Thank you!