Simple Power Bank Circuit for Charging Mobile Phones

This articles guidelines are used to create a portable phone charger circuit that is similar to those seen in stores.

Keeping a fully charged phone when traveling or out is a great idea.

From little chargers that fit in a pocket to bigger ones that can power several devices these chargers come in a number of sizes.

They are also capable of charging phones, iPads, smartwatches and even headphones.

Components for Power Bank Circuit:

Li-ion 7.4V 2600 mAh battery:

The 7.4V 2600 mAh Li-ion battery powers the mobile phone bank circuit.

When completely charged 8.2V is generated.

Voltage Regulator IC 7805:

One popular integrated circuit for controlling voltage is the IC 7805 which is a linear voltage regulator.

This circuits main objective is to reduce the Li-ion batteries 8.2V output to a constant 5V.

How to Build:

Parts List:

• Connect the Li-ion batteries positive connection to the 7805 input Vin.
• Join the Li-ion batteries negative terminal to the circuits common ground.
• Now the IC 7805 output Vout pin is steady for 5V.
• Use wires to connect the 7805 output to the USB ports positive terminals.
• Connect the 7805 ICs ground pin to the USB ports negative terminal.
• Attach the positive and negative USB port terminals to the correct mobile phone charging cable terminals.
• The USB ports must to be made to provide the standard 5V output for mobile phone device charging.
• Protection components like fuses or overvoltage protection circuits must be included depending on the design.
• Monitoring devices that show the batteries condition or the charging process like LEDs or voltage indicators should also be included.

In general the circuit uses the 7805 voltage regulator to step down the 8.2V or 8.4V from the Li-ion battery to a steady 5V output which is then sent to USB ports for charging smartphones or other smart devices while traveling outside.

Functioning with standard mobile device charging standards is thus guaranteed.

Components for Recharging the Power Bank Battery at Home:

9V AC-DC Converter:

With the help of this adapter the circuit gets powered constantly by 9V DC from the mains energy.

9V Zener Diode:

The TIP35 transistors base is fixed by the Zener diode which also supplies a steady reference voltage.

This circuit makes use of a 9V Zener diode.

TIP35 Transistor:

When fitted the TIP35 functions as an emitter follower.

The emitter in this configuration follows the base voltage less the forward voltage drop from the diode.

Connection Details:

Parts List:

• Connect the zener diodes anode to the 9V AC to DC positive terminal adapter.
• Fix the zener diodes cathode to the circuits common ground.
• Wire the zener diodes cathode to the TIP35 transistors base pin.
• Connect the TIP35 transistors emitter pin to the common ground.
• Join the TIP35 transistors collector pin to the Li-ion power bank batteries positive terminal.
• Make sure the Li-ion batteries negative terminal is connected to the ground.
• Feedback mechanisms like resistors or sensors are used to monitor the charging process and control the charging current depending on once needs.

Formulas and Calculations:

Following are few essential factors while using a power bank to charge a mobile phone battery.

Below are simple formula with an explanation:

Charging Time = Battery Capacity / Charging Current

where,

• The charging time (t) is the time needed to fully charge the battery of a mobile phone.
• Battery Capacity (C) which normally appears in milliampere hours (mAh) or ampere hours (Ah) is the capacity of the mobile phone battery.
• Usually expressed in milliamperes (mA) or amperes (A) the charging current (I) is the current that the power bank supplies to charge the battery of a mobile phone.

Example Calculation:

Assume that one have a 3000 mAh cell phone battery and that the power bank provides 1000 mA of charging current.

Charging Time = 3000 mAh / 1000 mA

Charging Time = 3 hours

To charge the mobile phone battery from 0% to 100% in this situation a power bank with a 1000 mA charging current may take around three hours.

Keep in mind that this is only a rough calculation and actual charging times can differ based on the circuits charging efficiency, the batteries starting state and changes in charging current over time.

Circuit Working:

The circuit receives a steady 9V DC input from the 9V AC to DC adaptor.

The zener diode maintains the TIP35 transistors base voltage at a steady 9V less the forward voltage drop which comes out to be about 8.6V at the base.

The output voltage of the TIP35 transistor in emitter follower voltage regulation mode is then around 0.6V lower than the base voltage.

For charging the 7.4V Li-ion power bank battery the output voltage thereafter drops to about 8.4V.

Both the battery and the TIP35 transistors emitter share a common ground and the Li-ion battery is connected to the transistors collector pin.

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.

When the battery is completely charged it is placed outside power bank which offers a practical means of charging cell phones in an emergency.

Conclusion:

This Simple Power Bank Circuit for Charging Mobile Phones contains information that is easier for everyone to understand if difficult calculations are avoided.

since the majority of users are more concerned with secure charging techniques.

It draws attention to the simple to use pre-built module options that can be used to avoid discomfort and save time.

Shorter explanations are simpler to read and preserve and there is less risk.

References:

Analysis of Specified Capacity in Power Banks

Powerbank