Simple Power Bank Circuit for Charging Mobile Phones

This article shows you how to build your own portable phone charger, like the ones you can buy at the store.

This is a great way to keep your phone charged when you are out and about.

These chargers come in all sizes, from small ones that fit in your pocket to bigger ones that can charge multiple devices.

They can charge phones, tablets, headphones and even smartwatches!

Components for Power Bank Circuit:

7.4V 2600mAh Li-ion Battery: This is the power source for the mobile phone bank circuit.

When fully charged, it produces 8.2V.

7805 Voltage Regulator IC: The IC 7805 is a popular linear voltage regulator IC that is used to regulate the voltage.

In this circuit it is used to step down the 8.2V from the Li-ion battery to a stable 5V output.

Connection Details:

Parts List:

Find out the components connections details mentioned below:

• Connect the positive terminal of the Li-ion battery to the input Vin of the 7805.
• Connect the negative terminal of the Li-ion battery to the common ground of the circuit.
• The output Vout of the 7805 is now a stable 5V.
• Connect the output of the 7805 to the positive terminal of the USB ports using wires.
• Connect the ground of the 7805 to the negative terminal of the USB ports.
• Connect the positive and negative terminals of the USB ports to the corresponding terminals of the mobile phone charging cable.
• The USB ports should be designed to provide the standard 5V output for charging mobile phones or smart devices.
• Depending on the design, you may want to include protection components such as fuses or overvoltage protection circuits.
• Monitoring components such as LEDs or voltage indicators can also be added to indicate the status of the battery or charging process.

Overall, the circuit takes the 8.2V or 8.4V from the Li-ion battery, uses the 7805 voltage regulator to step it down to a stable 5V and provides this 5V output to USB ports for charging mobile phones or smart devices during outdoor travel.

This ensures compatibility with standard mobile device charging requirements.

Components for Recharging the Power Bank Battery at Home:

9V AC to DC Adapter: This adapter is used to convert the mains electricity into a stable 9V DC power source for the circuit.

Zener Diode 9V: The Zener diode is used to clamp the base of the TIP35 transistor providing a stable reference voltage.

In this case, it is a 9V zener diode.

TIP35 Transistor : The TIP35 is configured as an emitter follower.

In this configuration the emitter follows the base voltage minus the diode forward voltage drop.

Connection Details:

Parts List:

Find out the connections details mentioned below:

• Connect the positive terminal of the 9V AC to DC adapter to the anode of the zener diode.
• Connect the cathode of the zener diode to the ground or common ground of the circuit.
• Connect the cathode of the zener diode to the base of the TIP35 transistor.
• Connect the emitter of the TIP35 transistor to the common ground.
• Connect the collector of the TIP35 transistor to the positive terminal of the Li-ion power bank battery.
• Connect the negative terminal of the Li-ion battery to the common ground.
• Depending on the requirements, you may include feedback mechanisms such as resistors or sensors to monitor the charging process and regulate the charging current.

Formulas and Calculations:

The charging of a mobile phone battery using a power bank involves a few key factors.

Here is a simple formula and explanation:

Charging Time = Battery Capacity / Charging Current

where,

• Charging Time (t): This is the time it takes to charge the mobile phone battery.
• Battery Capacity (C): It represents the capacity of the mobile phone battery usually measured in milliampere hours mAh or ampere hours Ah.
• Charging Current (I): It is the current supplied by the power bank to charge the mobile phone battery usually measured in milliamps mA or amperes A.

Example Calculation:

Let us say you have a mobile phone battery with a capacity of 3000 mAh, and your power bank provides a charging current of 1000 mA.

Charging Time = 3000 mAh / 1000 mA

Charging Time = 3 hours

So in this example it would take approximately 3 hours to charge the mobile phone battery from 0% to 100% using a power bank with a 1000 mA charging current.

Keep in mind that this is a simplified calculation and actual charging times may vary due to factors such as the efficiency of the charging circuit the initial state of the battery, and variations in charging current over time.

How it Works:

The 9V AC to DC adapter provides a stable 9V DC input to the circuit.

The zener diode clamps the base voltage of the TIP35 transistor to a stable 9V minus its forward voltage drop resulting in approximately 8.6V at the base.

The TIP35 transistor configured as an emitter follower voltage regulator, then outputs a voltage that is approximately 0.6V less than the base voltage.

Therefore, the output voltage becomes approximately 8.4V suitable for charging the 7.4V Li-ion power bank battery.

The Li-ion battery is connected to the collector of the TIP35 transistor, and the common ground is shared between the battery and the emitter of the TIP35.

This simple power bank battery recharger circuit allows for the controlled charging of the Li-ion power bank battery at home using a 9V AC to DC adapter.

Once fully charged the battery can be installed in the power bank for outdoor use providing a convenient way to charge mobile phones during emergencies.

Conclusion:

In this Simple Power Bank Circuit for Charging Mobile Phones a general audience will find the information easier to understand if complicated formulas are avoided.

Since safe charging procedures are what most consumers are most concerned about, they are emphasized.

It draws attention to the easily accessible and intuitive pre built module options, which may be used to save time and possibly avoid annoyance.

Shorter explanations are easier to read and retain, and they also pose less of a threat.

References

Analysis of Specified Capacity in Power Banks

Powerbank