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    This is the simple and easy way to tap current from a Motor Bike battery to charge the Mobile Phone. Most of the Mobile Phone battery pack has three 1.2 volt cells making the voltage to 3.6 volts. For fast charging of the battery pack, each cell requires more than 1.2 volts and sufficient current. This circuit can deliver 5 volts at 300 mA to charge the battery quickly. The circuit is Voltage and Current regulated and with Polarity and Surge protection components.

    Mobile Charger using Bike Battery Circuit Schematic

    The circuit uses a Positive Voltage regulator IC 7805 to give 5 volt regulated output. The components around IC1 are meant for protecting the IC so as to give smooth output power. Zener diode ZD act as the Input Surge protecting diode. It provides 7.2 volts to the input of the regulator IC from the 12 volt bike battery. Diode D1 is the Output Surge and Input Short protecting diode.

    When a surge voltage exceeding maximum voltage rating of the regulator is applied to the input or when a voltage in excess of the input voltage is applied to the output, the regulator will be destroyed. If the input terminal shorts with the ground, the output voltage increases above the input voltage(ground potential)and the charge in the capacitor connected to the output flows into the input side which is also fatal to the regulator. Both these situations can be avoided by using the Zener at the input and the diode D1 across the regulator. Capacitor C1 and C2 provide stability to the regulator and these should be soldered close to the legs of the regulator. Capacitor C3 act as a buffer to give constant voltage in the output.
    7805 Datasheet

    7805 IC can tolerate maximum 35 volts and its current rating is 1 Amps maximum. Resistor R1 restricts the charging current to around 330 mA as per the Ohms law. Even if the current is low, charging process will not be affected. Slow charging with 80 to 100 mA current is generally advised. But in case of an emergency, quick charging can be done with high current

    Assemble the circuit on a Perfboard and enclose in a small case that can be fitted near the Bike battery. Use suitable pins to connect with the Mobile phone. Charging current can be tapped from the battery using Alligator Clips. Before using the circuit, double check the connections especially the polarity of connectors and measure output voltage and current using a Digital Multi Meter. The same circuit can be used for charging Mobile battery from 12 volt Car battery or from a 12 volt Solar panel.

    IC 7805 Pin connection and Alligator Clips

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    25 Responses to "Cellphone Charger Using Bike Battery"

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    1. J M Fahey says: on March 24, 2010 at 1:14 am

      This circuit has obviously never been built.
      The 7.2V Zener diode wil explode the very second it is connected to a 12V battery.

    2. D Mohankumar D.Mohankumar says: on March 24, 2010 at 2:11 am

      See the Precautions on Applications of 7805 in the data sheet provided along with the circuit

      • resistors 15R 1W AND 100R 1W drops the output current below 60mA. ie insufficient current for proper charging. change the resistors values. i think maximum current drawing without resistor is 800mA and will reduce with charging. without resistor also good

    3. Dear sir
      I have worked with you circuit.but i did’t get proper output. i want to know about following things in your circuit .why you r using zener diode & 100 ohm resistor & 15 ohm resistor.do u have any other circuit for design motor bike charger

    4. nouman nayyer says: on July 6, 2010 at 10:15 am

      i want to ask u some thing
      mobile phone needs 3.7 volts to charge.
      but 78l05 regulates 5 volts???

      • Swapnil says: on June 28, 2012 at 6:25 am

        Actually, mobile phones can be charged in the range of DC 5 – 12 V range. But if the battery is constantly charged at higher voltages, it’s life will be reduced.

        The 3.7 V specification is for prolonging the battery life. However, we have to keep the phone charging for a long amount of time with this voltage. So, the IC 7805 is used.

    5. sir did u have charger prepared from smoke from the bike

    6. sir is there any mini project ckt on mobile charger

    7. electronics baics

    8. the Zener diode ZD start heating when we apply 12v to the circuit.. there must be some change in the circuit…

    9. Sir, what if the output current is just a few mA in the given circuit and we have to increase it upto 300mA ?

    10. could send me the project report of this

      • Adnan Rafiq says: on December 7, 2011 at 1:01 pm

        i am a electrical engineer.if you are a pakistani.then sent me text message.my phone number is +923327929262.i will contact you.

    11. this is waste circuit da kunju paya

    12. fucking circuit

    13. can I have a detailed working material for this project???if so send it….

    14. I was from Philippines,an electronics technology student.Thank YOU for this I will try to make it because our place was sometimes having a brown outs.

    15. sir,Is it tested?

    16. narayana behera says: on October 23, 2013 at 4:57 am

      sir pls tell me how can i get more current than 330mA for which mobile battery quickly charged

    17. narayana behera says: on October 23, 2013 at 5:00 am

      sir pls give me some ckts like cfl drive by using 6V battery via my email

    18. ravikiran says: on December 2, 2013 at 11:57 am

      sir it is succussfull but “IC7805″ is very tooomuch heatincress connected to mobile why sir ? plz reply via mailid……..

    19. samir pandya says: on June 25, 2014 at 10:55 am

      thenk’s sir

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