Inside a power bank. So what is a power bank exactly?

How To Make Power Bank Circuit On PCB

These days On Power Bank Circuit On PCB, digital products are being in immense demand. However, there are some products that you can make in your home with little things that you would get from the market. One such product is the power bank circuit. The power bank circuit composition is straightforward and can be made with little effort. There are numerous uses of the power bank circuit; for instance, you can use it as a spare power bank if you need it.

There are numerous ways to make the power bank circuit; e.g. one of the easiest ways is to use a boost converter for making the power bank. However, another easy way to make the power bank circuit is by using different modules that can be used to charge the cell phone.

A technique to make the Power Bank Circuit

This project is revolving around the making of the charging circuit from scratch. First of all, the basic circuit schematics are being made, which is then simulated. After debugging all the drawbacks of the circuit, its PCB is designed, which is then etched, and components are placed to make it work.

The Main Components Required

The following is the list of main components required for the project.

  • PCB board.
  • IC of TP4056
  • XL 6009
  • Inductors (33uH)
  • The female connector (USB)
  • Charging pin (Female/Mini USB)
  • Burg stick
  • Capacitors (1uF, 10uF, 220uF, 100uF, and 47uF)
  • Variable resistor of 5K ohms.
  • Lithium Cell 18650
  • LEDs
  • Diodes 1N5824
  • Resistors (1K ohm, and 1,2 K ohms)

Block diagram of a typical power bank circuit:

Block diagram of a power bank primarily consist of three main functions as shown in the above image: A charge controller, 5v boost converter, Li-ion battery.

a) Battery charge controller circuit:

The function of the battery charge controller circuit is to control the state of charge of any battery according to its capacity and rated voltage. Other than this, it also helps battery against overcharge. Here, a lithium-ion charger module which is based on IC TP4056/ TP4054 is used and a micro USB port to charge the battery is present.

The battery charge controller module TP4056 in the image is designed keeping in mind the highly critical li-ion batteries and reduced manufacturing time and cost by using SMD components.

b) A 5-volt boost converter circuit:

The function of the 5-volt DC-DC boost converter circuit is to convert the lower voltage of a battery to 5v regulated DC. Here, it converts 3-3.7 v DC obtained from LI-ion batteries (std. 3.7 volt is rated) to steady 5volts so that our mobile charges at standard voltage normally.

A DC-DC boost converter comes with a female USB port to connect a USB cable from our mobile phone to it. The boost converter module works on the principle of (PFM) Pulse Frequency Modulation.

Check this interesting video below on working of power bank:

c) Rechargeable lithium-ion batteries:

Everybody knows the function of batteries, the only thing to consider is to use rechargeable batteries aiming at re-usability. The battery pack in power bank is a combination of 3.7 volt li cells connected in parallel. The 18650 cells are the most commonly used Li-ion cells in the market these days. Some power bank brands use flat li-ion cells to make it thin and compact.

d) Battery level display unit (optional):

The display unit may be or may not be present in a power bank as it adds the extra cost to the product company prefer to eliminate it in low-end products. The battery level display unit has two functions, first is to show the state of charge in percentage (%) and second is to indicate charging of both mobile phone and power bank.

Working: The power bank is a simple power backup device for your iPhone which is portable/ handy instantly to charge a phone when the battery is low.

The charge controller charges the battery to its appropriate level and protects it from damage caused due to overcharging. Our mobile phone’s battery needs 5volt dc at 1 A or 2 A but cells inside the p-bank have the maximum output voltage of 3.7 volts. Thus a boost converter boosts up the level to 5Volts which is required to charge a phone. The modules come with an input port (micro USB) for charger and output ports (USB female) for mobile charging.

Watch how power bank circuits and controllers work at the end of this post.

Power Bank circuit using module TP-4056 and a 5v boost converter:

In this circuit, a total of 3 lithium-ion cells are used. All batteries are connected in parallel with each other connection to increase backup of a power bank.

As we know that in parallel connection of batteries voltage remains the same but current capacity is increased. So for increasing the current all batteries must be connected in a parallel configuration.

Connection: Assemble all li-ion cells 18560 in a parallel configuration and put it into a casing or just tape it. Means solder positive terminal of one cell to the positive terminal of other cell and negative terminal to the negative terminal. Now we have two wires one is red positive and black negative wire. Connect the black wire to negative of 5v boost converter module and to controller module TP4056. Similarly, connect positive terminal from battery to positive terminal of both the modules.

Keep in mind, the marking on the module and – accordingly connect wires. You can put all these components in an assembly case. Its done DIY power bank is ready to use, make sure you charge it completely before using it for 1st time.

Power Bank circuit using dual USB output port module:

In this circuit we will use all in one module, it comes with dual USB 5volt 1A/ 2A rating. Various modules for this function from the different manufacturers are available with slight change in specification.

Connection: Assemble all 18560 rechargeable cells in a parallel configuration as mentioned above. Means solder ve terminal of one cell to ive terminal of other cell and a negative terminal of one cell to negative terminal of other. Connect the black wire from battery to negative terminal of this dual USB out power bank module. Similarly, connect ive terminal from battery to ive terminal these modules.

There are markings on the module as and – symbols make sure you follow the circuit diagram

Electronics Projects: Power Bank for Smartphones

This power bank can be used for charging smartphones. This power bank circuit uses two integrated modules and a lithium-ion battery. The first module is a lithium-ion battery charger and the second is a DC-DC boost converter module.

Circuit diagram of the power bank is shown in Fig. 1. It consists of a USB lithium-ion charger module (USB-IN), 3.7V/2600mAh lithium-ion battery (BATT.1), on/off switch (S1) and DC-DC boost converter module (USB-OUT).

Here, a lithium-ion charger module based on TP4056 IC, rechargeable lithium-ion battery (Samsung type 18650) and DC-DC converter module based on pulse frequency modulation (PFM) technology are used.

The battery charger module, shown in Fig. 2, is designed around a dedicated lithium-ion battery charger TP4056 chip and populated with SMD components. This onboard charge controller chip handles BATT.1 charging operation by processing the 5V DC input supply received through the USB socket (or through IN and IN- terminals). Output terminals (BAT and BAT-) can be directly connected to BATT.1. Two onboard SMD LEDs located on top of the circuit board provide charging-status indications.

BATT.1 is used as the power reservoir. Since only 3.7V DC supply is available from BATT.1, DC-DC boost converter is used to cater to the stable 5V DC supply at output. If input voltage of 0.9V to 5V DC is available, this converter gives stable 5V DC output through its USB socket, with conversion efficiency up to 96 per cent.

The DC-DC boost converter module, shown in Fig. 3, is an SMD module with a PFM chip at its heart. Input DC supply fed through input terminals ( and.) is processed by this dedicated chip to give a stable USB standard DC supply via the standard USB socket at its output. An onboard SMD LED, fitted near the input terminals, works as a power-status indicator. Switch S1 is included to route DC supply from BATT.1 to the converter.

Operation application

Almost all smartphones look for signals/levels on D and D- of the USB interface that indicate the charger’s current capability. A full-speed device will use a pull-up resistor attached to D, as shown in Fig. 4, to satisfy itself as a full-speed device. The pull-up resistor at the device end will also be used by the host or hub to detect the presence of a device connected to its port. Without this resistor logic, the USB assumes there is nothing connected to the bus.

In case of a charging error, pull down D line of the USB output socket (in converter module) with the help of a 200-kilo-ohm resistor as shown in Fig. 5.

Construction and testing

Assemble all components of the power bank circuit as per Fig. 1. Follow the testing operation given below:

Connect the charger module to CON1 (USB-IN) either through an AC adaptor or provide 5V DC supply through a PC or laptop using a USB cable for charging BATT.1.

Connect BATT.1 across CON1 for charging. A red-coloured LED will turn on, showing the charging status of BATT.1. When the battery is fully charged, a blue-coloured LED will turn on. You may remove the charger connected at USB-IN.

You can now charge your smartphone by connecting it to the USB socket of the converter module (USB-OUT) using a USB cable and closing switch S1. A red-coloured LED of the converter module will turn on, showing the charging status of the smartphone.

EFY note. Connect the terminals of BATT.1 to USB-IN and USB-OUT with correct polarity.

T.K. Hareendran is an electronics hobbyist, freelance technical writer and circuit designer

To read other exciting Electronics Projects: click here

This article was first published on 12 December 2016 and was recently updates on 26 December 2018.


Capacity is perhaps the most important factor to consider when buying a power bank.

Power banks vary widely in their energy storage capacity, which will dictate the number of times that a power bank will be able to fully recharge a particular device until its reserves are exhausted.

Having a power bank with ample capacity is important when you’re travelling, as there will likely be occasions when you’ll be unable to access a working power outlet for a considerable period of time (such as during 40 hour long train journeys in India where the power outlets on the train refuse to work).

In scenarios like these, a portable battery charger with inferior capacity won’t always cut it – it’s better to have the extra capacity and not need it, than need the extra capacity and not have it.

power, bank

Power bank capacity is normally measured in milliampere hours, denoted as mAh, though this is a unit of measurement that can be quite misleading. (we discuss why below).

If you only intend to use the power bank to charge your smartphone, we generally recommend buying a power bank with a nominal capacity of 10,000 mAh, as this amount of juice will fully charge most smartphones 3. 4 times (and most tablets 1- 1.5 times).

A good rule of thumb for travel is to buy a power bank with a stated capacity that’s 3-4 times that of your device’s battery. You will therefore need a power bank with a much greater capacity if you plan to use it to charge a tablet or other device with a larger battery.

Okay, so let’s say your smartphone battery is rated at 2,000 mAh and your power bank is rated at 10,000 mAh. In that case, you should expect it to fully charge your phone five times, right?

The reason for this is that there are various conversion losses and you normally need to knock-off around 25-30% of the nominal capacity to get an estimation of the real working capacity of the power bank.

So for a 10,000 mAh power bank, the real working capacity might be closer to 7,500 mAh and thus it will only charge your 2,000 mAh smartphone battery somewhere between three and four times.

power, bank

Energy is lost inside the PCB (printed circuit board) of the power bank, in the charging cable and also inside the internal charging circuitry of your device.

These losses usually account for about 10% of the total losses, although

high-end power banks can have total conversion losses of less than 10%. Xiaomi power banks for example are known to be particularly efficient.

However be careful when a manufacturer states that the conversion rate is X %, as this number often only refers to the efficiency of the PCB and not the overall conversion rate taking into account all energy losses in the system.

But the biggest loss of capacity comes from the voltage conversion process that occurs inside the power bank. To explain this, we have to first understand what mAh actually means.

The mAh value is not actually measuring the energy storage capacity of the power bank.

What it means is that the power bank can supply a current of 10,000 milliamps for a period of one hour at the particular voltage that the power bank battery supplies.

But because power bank batteries supply 3.7 V and USB supplies 5V, a voltage conversion takes place inside the battery pack when you use it to charge your device.

At the new higher voltage (5V) the power bank can no longer supply 10,000 milliamps of current for one hour, so there’s a reduction in the mAh value of the battery pack.

Therefore if we want to determine how many times a power bank will charge our device, we are really only interested in knowing the mAh value of the power bank at 5V, not the nominal mAh value, which is only valid for 3.7V.

The correct and universal way to measure electrical storage capacity is not with mAh but with watt-hours or Wh, a unit which denotes how much electrical power a battery can supply for one hour.

To calculate the true energy storage capacity of a power bank, we must factor in not only the mAh value, but also the voltage that this can be supplied at.

Watt hours = mAh x Voltage/1000

For more info on how to calculate the real capacity of a power bank, see this page.

There are a few additional factors that can affect the capacity of your power bank.

A power bank that charges devices at faster rates can also incur higher conversion losses, although that’s a trade-off you’re probably willing to make for getting your device charged quicker.

Leaving your power bank in extremely cold or hot environments can also cause it to lose stored energy or can even permanently damage the battery.

power, bank

Stored energy will also be lost over time if you neglect to use your power bank due to a phenomenon known as self-discharge.


Carry-on travellers in particular have to consider the weight of a power bank, since rather ungenerous weight limits apply to hand luggage that’s to be taken on board many airlines, and many chargers are not.friendly.

A power bank may not weigh all that much on its own but it could still be the final straw that breaks the camel’s back.

A heavy brick in your is also cumbersome; it forces you to tighten your belt or pants drawstrings to prevent your drawers from ending up around your ankles, and it annoyingly bounces around inside your if you try to run.

Portable battery packs tend to get heavier as their capacity increases, with the 20,000 mAh chargers starting to become, in our opinion, too unwieldy for travel.

We feel that the 10,000 mAh power banks strike the best balance between charging capacity and weight. A reasonable weight for a power bank of this capacity would be anywhere in the region of 150 – 250 grams.

If you’re a device power user or really need a high-capacity power bank for whatever reason, you may be able to justify carrying something heavier.

In general, the lighter the better but beware of power banks that are abnormally light, as this could be a warning that the inner components, such as the battery or safety mechanisms, are severely compromised.


A more compact power bank easily slides into s, pouches and backpack compartments and leaves more space in these places for other important items.

A compact power bank can also fit more easily in your trouser s, making it easy to use your phone as normal on the go while it’s charging from the battery pack in your (with the cable running between them).

The general rule here is that smaller is better, as long as the capacity is sufficient for your personal needs. And if you use devices in moderation when you travel, a high-capacity power-bank is not necessary for you.


The power bank design that you decide to go with is influenced by personal preferences to a large extent, but design can also have important practical consequences and can impact the user-friendliness of the product.

Power banks vary in shape, though most are more or less rectangular with varying degrees of thickness. seldomly you’ll come across power banks that are cylindrical, oval (in cross-section), cuboidal or even totally whacky shapes. We’ve even seen a power bank shaped like a red hot chili pepper.

A relatively sleek design makes it easy to slip a power bank into a tight or backpack sleeve, though we find the somewhat thicker models still fit just fine in our roomy trouser s.

Rounded edges not only look elegant but also allow the power bank to be held comfortably in the hand, and you will often find yourself holding the power bank and phone together in your hand when the phone is charging and you need to use it.

Consider the location of the charging ports too. If the input and output ports are situated very close together, it could be difficult to plug cables into both of these ports at the same time.

This might make it difficult to avail of pass-through charging (charging your device from the power bank while the unit simultaneously charges from the mains), even if the power bank supports it.

Aesthetics probably matter more to most of us than we care to admit. Choose a colour and an overall look that you find aesthetically pleasing, so that you don’t regret your decision later. Also, examine the product all over; one face may sport a big logo or brand name that’s going to annoy you.

Glossy, polished surfaces are more vulnerable to scratches and showing up fingerprints than matte surfaces. Remember also that a power bank in a darker colour like black will do a better job at masking scratch marks, fingerprints and damage to the shell.

How does a power bank work?

You can charge your power bank using a USB connection via a mains supply, or wirelessly if enabled. The charge is then stored in the power bank until it is withdrawn when you use it to charge a device. Whilst the capacity of each power bank is different, they eliminate the need to carry a regular, mains-power charger with you because power banks can store enough energy for multiple charges.

Whilst power banks may appear unassuming, there is complex circuit technology stored inside. Besides recharging your devices, they also have safety features to prevent overcharging and short-circuiting, as well as quick charging and wireless technology.

Power bank capacity

All power banks are different even though, on the surface, many look similar. Typically, when it comes to discussing power bank batteries, units will fall into one of two categories focused on lithium technology. All power banks use rechargeable batteries, but one may use lithium-ion whereas another may use lithium-polymer. The most significant difference between the two types is the chemical electrolyte between their positive and negative electrodes. This boils down to lithium-ion holding a higher power density and a lower cost compared to lithium-polymer. However, lithium-polymer batteries are more robust, flexible, and have a lower chance of suffering with leaking electrolyte.

Both forms of battery work effectively and have their pros and cons. However, it will largely depend on the design and manufacturing of a power bank as to whether it delivers the charge you need.

Below, MAGFAST highlights the most important points to consider when purchasing a new power bank.

How is power bank capacity calculated?

Power bank capacity is measured in milliampere hours (mAh). The higher the number of mAh the more charge the power bank holds for you to withdraw when you use it to charge your devices. Once the power bank capacity has been drained it will need to be charged up again. The general rule of thumb dictates that smaller power banks have a typical capacity of 1,000 mAh and medium units have 3,000 to 5,000 mAh. Larger power banks can reach 10,000 mAh.

What sets MAGFAST apart from other power bank manufacturers is our ability to deliver serious power. MAGFAST Life is our neat, portable power bank that is great for life ‘on the go’. Whilst its counterparts have an average capacity of 1,000 mAh, Life has a capacity of 6,000 mAh. That’s enough power to charge a dead iPhone battery twice.

At the opposite end of the scale is MAGFAST Extreme – the one that can jump-start your car. Extreme is a super-charger with the power to boost your battery life for days due to its staggering 18,500 mAh capacity. It is also the world’s first portable charger with three Qi wireless charger stations – ideal for all your devices or when sharing with family or friends.

Both MAGFAST Life and Extreme have four ways to get power in. Life has five ways to get power out whereas Extreme has six: the added bonus of Extreme is the 12volt 500amp outlet. This means you can use MAGFAST Extreme to jump-start your vehicle over, and over, and over again. Simply invest in MAGFAST’s 12v jumper cables to accompany Extreme and you can rest assured you’ll never be stranded with a dead vehicle battery.

Whilst Extreme has the endurance to provide you with power for days, there are different power banks available with MAGFAST to suit your capacity requirements.

Do I need a phone power bank?

Do you often find yourself running out of phone battery during the day? Are you sick of having to hunt for a mains-power socket when the dreaded warning pops up? Having a charged smartphone is important, particularly when on the go. There are an immense number of scenarios when we need to stay connected, such as for meetings, directions, studying, or socializing. Power banks enable you to charge your device on the go without the need for a mains supply, whether you’re in the car, on the train, at the airport, or even on an airplane.

Can I take my power bank on a flight?

Taking your power bank on a flight is acceptable. However, there are conditions in place for the safety of crew and passengers.

  • Power banks must be stored in your hand luggage
  • The battery should be 100 Wh or under
  • Batteries between 100 Wh and 160 Wh will need a special permit
  • The Wh output should be visible on the device

MAGFAST’s super-charger, Extreme, has a 68.45 Wh battery, making it perfectly fine to use on an aircraft as long as it is stored in your carry on. All of MAGFAST’s power banks, including Life, Extreme, Apple Watch charger Time and car phone charger MAGFAST Road can be taken onboard.

Wireless charging power bank

Qi is the most popular type of wireless charging and it is the universally agreed global standard. This is why all of MAGFAST’s power banks facilitate Qi wireless charging of your enabled devices. You can find out more about the most popular cell phones in relation to wireless charging via our comprehensive guide.

Qi can provide you with the ability to charge your devices anywhere, any time. Qi devices and Qi chargers are undoubtedly the most celebrated technological advancement of the past decade as people yearned for a more convenient way of charging their device’s batteries that was cable- and clutter-free. Qi wireless charging means you can boost your battery at home, in the office, or car, whilst also providing the ability to power up on the go in coffee shops, at hotels, and airports.

Never worry about running out of battery ever again

We are sure that, one day, you’ll be able to charge your devices with your own pulse – or something equally mind-boggling. Until then, power banks are a pivotal solution for delivering power time and time again to keep your devices charged on the go. Gone are the days of battery anxiety. Now, as a true power bank expert, you can make an informed decision on the best solution for you. We don’t mean to be biased, but with MAGFAST changing charging for good, we know our power banks can deliver above and beyond your needs.

How much is a power bank?

There is no set price for a power bank. However, investing in a high-quality power bank will ensure you can charge your devices for years to come. You can pick up a cheap power bank for just a few s but why run the risk of the power bank breaking or damaging your device when there are tried and tested solutions available. Opting for a MAGFAST power bank gives you peace of mind that you’re buying a power bank that is technologically and visually perfect.

MAGFAST power banks vary in price, from 99 for MAGFAST Life to 249 for MAGFAST Extreme. All of our products are designed to work together, so you can easily create a bespoke MAGFAST charging experience by investing in our other products too. A neat solution, the MAGFAST Family Pro Kit (297) contains Life, Extreme, Road, Air, two Walls and a myriad of accessories. If you were to buy all the components of the MAGFAST Family Pro Kit separately, that would total 606 – and that’s without the cost of added accessories! By investing in the MAGFAST Pro Kit you will be saving over 300! If you’re serious about charging and want more options than a stand-alone power bank, then the Pro Kit collection is for you

Does MAGFAST offer an Apple power bank?

All MAGFAST’s power banks are compatible with Apple devices, from iPhones to iPads and beyond. MAGFAST Time is a genius piece of kit, providing a power bank solution for portable wireless charging of the Apple Watch.

Does MAGFAST offer an iPhone power bank?

MAGFAST’s power banks can be used with the iPhone 8 and all later handsets, as well as newer smartphones from all major brands. However, it is worth bearing in mind that wireless charging can only take place if your smartphone is wireless enabled. If not, it’s no issue, since all of MAGFAST’s power banks have multiple ways of charging up your device thanks to the handy output choices.

What is the best small power bank to buy?

Without a doubt, MAGFAST Life is the best small power bank on the market. Whilst most.sized power banks only have a capacity of 1,000 mAh, Life has a capacity of 6,000 mAh. This means six times more power packed into a product that is perfect for on the go charging.

Can I create my own bespoke MAGFAST charging solution?

MAGFAST’s products are equipped with amazing magnetic technology. This means each MAGFAST family charger can be connected with another to create a charging solution that suits your needs perfectly. Whether you use your MAGFAST power bank separately or connected with another MAGFAST component, you will receive the same unmatched power and durability wherever you are.

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