## What is the real output capacity of a Power bank?

Do you know how many times you can recharge your cell phone with a 10000mAh or a **20000mAh** power bank?

A very common mistake among those of us who want to know the number of charges we can get on our devices with a power bank is to divide the capacities of both devices, i.e.:

Number of Charges = Power Bank Capacity (mAh) / Smartphone Capacity (mAh)

For example, if you have a smartphone with a 2500mAh battery capacity and you want to buy a 10000mAh power bank, how many charges could you get?

If we apply the above formula we get 4 full charges:

Number of Charges = 10000 mAh / 2500 mAh = 4 charges

THAT’S A BIG MISTAKE!!

We are sorry to tell you that this calculation would be incorrect because the 10000mAh of the power bank refers to the capacity of its internal battery.

A result closer to reality would be to use the actual capacity available at the output USB port of the power bank:

Number of Charges = Actual Power Bank Capacity / Smartphone Capacity

If we assume that the actual capacity is 6000 mAh we would have enough juice for 2 full charges of our smartphone:

Number of Charges = 6000 mAh / 2400 mAh = 2,5 charges

Although this second formula is still technically incorrect (capacities divide at different voltages) we wanted to make you see in a simple way that the number of charges is much lower than expected despite the fact that the power bank is advertised with a capacity of 10000 mAh.

And this is the main problem that many Amazon users encounter when buying a power bank:

In the following article, we are going to explain in depth how to calculate the actual capacity and the number of charges of a power bank in any device and for different charging voltages.

Although the content of this article may be a bit technical and boring to read, we have tried to make it as easy to understand as possible for anyone without previous experience.

After reading this article you will become a power bank expert!

- 1 Which are the components of a Power bank?

- 1.1 Battery capacity and voltage rating
- 1.2 USB Output port voltage
- 1.3 To sum it up

- 2.1 Stored energy
- 2.2 Voltage conversion
- 2.3 Energy efficiency
- 2.4 Usable Energy and Real Capacity
- 2.5 To sum it up

- 3.1 Comparison of real vs. theoretical data
- 3.2 real-world examples: The PowerBank20 project
- 3.3 Conclusions

- 4.1 Example: How many charges are 10000 mAh?

- 4.1.1 Data validation

OTHER GUIDES YOU SHOULD READ

## Which are the components of a Power bank?

First of all, you should get familiar with the 2 basic elements that make up a Power bank:

- A rechargeable battery of a certain capacity (mAh) and nominal voltage (V).
- An electronic circuit that controls the charging and discharging process of the rechargeable battery, as well as performing other important functions such as, for example, protection against over-voltage, over-discharge, temperature control, etc.

As we will see below, the actual output capacity of a power bank will depend on the quality of such components.

### Battery capacity and voltage rating

The battery of a power bank consists of lithium-ion (Li-Ion) or lithium polymer (LiPo) cells.

Usually, they use cells with a nominal voltage of 3.7 volts (V) and a capacity ranging from 1500 to 5000 milliampere-hours (mAh). However, cells with other voltages are also available on the market, e.g., 3.6V, 3.8V or 3.85V.

Additionally, the battery may be made of a single cell or several cells connected together:

If the power bank battery is made of a single cell, its capacity and rated voltage will be the same as that of the cell itself.

If the power bank battery is made up of multiple cells, its capacity and voltage rating will depend on the individual capacity and voltage of each of the cells as well as the configuration used (series or parallel circuits) to connect the cells together.

Generally, a power bank battery uses cells with the same capacity and voltage nominal connected in parallel.

With a parallel connection, the voltage of the power bank battery is the same as the voltage of the cells and its capacity is the sum of the individual capacity of each of the connected cells.

In the previous image, we see an example with 4 cells of lithium-ion (Li-Ion) of 3.6V and 3400mAh have been connected in parallel resulting in a battery with a capacity of 13600mAh and a voltage of 3.6V.

Therefore, if we wanted to make a power **bank** using 3400mAh and 3.6V cells connected in parallel, the battery will have a voltage of 3.6V and its capacity will depend on the number of cells used:

- 1 cell: 3400 mAh/3.6V
- 2 cells: 6800 mAh/3,6V (2 x 3400 mAh)
- 3 cells: 10200 mAh/3.6V (3 x 3400 mAh)
- 6 cells: 20400 mAh/3.6V (6 x 3400 mAh)
- 8 cells: 27200 mAh/3.6V (8 x 3400 mAh)

So, from now on, whenever you see the capacity of a power bank advertised, remember that it refers to the capacity of its internal battery!

### USB Output port voltage

We have already seen that a power bank is composed of an internal battery of a certain capacity (mAh) and nominal voltage (V) which is usually 3.7 volts (V).

However, when charging a device with a power bank we should know that the USB output port of any power bank works at a standard voltage of 5V.

Even this voltage can be higher (9V, 12V or 20V) if both the connected device and the power bank support fast charging protocols such as Quick Charge (QC) or Power Delivery (PD).

This difference between the battery voltage and the power bank output voltage is the reason why the capacity of a power bank at its USB output port is different from the capacity indicated on its internal battery.

For example, a 10000mAh power bank would have a capacity of 7400mAh at its USB output port at a charging voltage of 5V.

### To sum it up

In this section we learned that:

- A power bank is made up of an internal battery (consisting of one or more Li-Ion or LiPo cells) and an electronic circuit.
- The capacity advertised on a power bank indicates the capacity of its internal battery and is different from the capacity available at the output port.

## How to calculate the actual output capacity of a Power bank?

Once we are familiar with the main components of a power bank, let’s learn a step-by-step method to calculate the actual output capacity of a power bank for any charging voltage (or output port voltage).

Additionally, to better understand the theoretical concepts, each section will have a practical example using the real data of a power bank of 10000 mAh capacity, the Ugreen (model PB178):

The specific data we are interested in knowing about this model are the capacity (mAh) of the device and the voltage (V) of its battery:

Later, we will also explain what the Rated Capacity data means, which some manufacturers are starting to include in the specifications of their power banks.

### Stored energy

As we already know, a power bank is an electronic device that stores energy in an internal battery to later transfer it to the battery of other devices, or even power some of them.

This energy is measured in watt-hours (Wh) and is calculated by multiplying the capacity (mAh) by the nominal voltage (V) of its internal battery:

Stored energy (Wh) = [Battery capacity (mAh) x Nominal battery voltage (V)] / 1000

The power bank in the image had a battery capacity of 10000 mAh and a nominal voltage of 3.85 V. To find out how much energy it stores we apply the above formula:

Power Bank Stored Energy = 10000 mAh x 3,85V = 38500 mWh / 1000 = 38,5 Wh

We see that our power bank stores 38.5 watt-hours (Wh) of energy that we can use to recharge the battery or power other devices.

### Voltage conversion

During the process of charging a device, the electronic circuit of a power bank raises the nominal voltage of the battery (e.g., 3.7V) to the voltage of the USB output port (5V standard voltage).

If we assume that the voltage conversion (from 3.7V to 5V) was an ideal process, i.e., without energy losses, all the energy stored in the power bank battery should be completely transferred to the USB output port.

Therefore, we can define the following equivalence:

Power Bank Stored Energy = Power Bank Output Energy

Let’s deconstruct this equation in terms of capacity and voltage:

Battery Capacity (mAh) x Nominal Battery Voltage (V) = Output Capacity (mAh) x Charging Voltage (V)

From the above equation, we know all the variables except the capacity at the USB output port.

If we solve this variable, we get a first approximation to know the real capacity at the output port of a power bank according to the voltage at which the device is charged (5V being the standard voltage):

Output Capacity (mAh) = [ Battery Capacity (mAh) x Nominal Battery Voltage (V) ] / Charging Voltage (V)

If we apply this formula with the data of our power bank (10000 mAh and 3.85 V) we will obtain a capacity of 7700 mAh at the output port at a charging voltage of 5V:

Output Capacity = (10000 mAh x 3,85 V) / 5 V = 7700 mAh

Furthermore, we can see that, although the capacities are different (10000mAh and 7700mAh), the energy is conserved at the input (battery) and output (USB port) of the power bank as we have considered that the voltage conversion process during the charging of a device is ideal (without energy loss):

10000 mAh x 3.85 V = 38500 mWh = 7700 mAh x 5 V

### Energy efficiency

So far, we have calculated the actual capacity of a power bank at its output port considering that it is able to supply 100% of the energy stored in its battery.

However, we are sorry to tell you that the formula defined in the previous section is never going to be fulfilled in real life:

Power Bank Stored Energy ≠ Power Bank Output Energy WRONG!

If the battery used is a low-quality one, it will lose a fraction of its capacity after a few power bank charge/discharge cycles.

Consequently, the power bank will have less energy available to supply to your devices.

During the voltage conversion stage performed by the power bank’s electronic circuit, part of the energy stored in its battery will be lost in the form of heat (this is known as The Joule Effect).

For this reason, the less efficient the electronic circuit is, the more energy will be lost and, therefore, the power bank will have less energy available to supply to your devices.

We can define the discharge energy efficiency of a power bank as the ratio between the energy supplied at its USB output port and the energy stored in its battery:

Power Bank Energy Efficiency (%) = 100 x (Output Energy / Stored Energy)

It should be clear that the energy efficiency of a power bank will never be 100% :

Even if we buy a new power bank and its battery is in perfect condition, there will always be an energy loss due to the voltage conversion process performed by the electronic circuit of the power bank in order to charge a device.

This energy loss will be higher or lower depending on the quality of the electronic circuit.

In Example 2 we calculated the actual output capacity of a power bank assuming that the voltage conversion process (from 3.85 to 5 V) was ideal, i.e., it occurred without energy loss.

Consequently, the power bank supplied 100% of its stored energy:

(Ideal) Energy Efficiency = Output Energy / Stored Energy = 38480 mWh / 38480 mWh = 1 x 100 = 100%

However, we already know that, actually, during the voltage conversion process some of the stored energy is lost, therefore, the efficiency will always be under 100%.

To calculate the actual energy efficiency of our power bank, let’s assume that we have measured the energy obtained at its output port:

(Real) Energy Efficiency = 28875 mWh / 38500 mWh = 0.75 x 100 = 75%

As we can see, the power bank has been able to supply 75% (28875 mWh) of the total energy stored in its battery (38500 mWh) while the remaining 25% (38500 – 28875 = 9625 mWh) has been lost as heat.

### Usable Energy and Real Capacity

Once we know the concept of energy efficiency in a power bank, we are ready to calculate the energy and capacity it will have at its USB output port.

With the Energy Efficiency formula as our starting point, we take the Stored Energy variable to the other side of the equation and, in this way, we get the energy available at the output port of the power bank:

Power Bank Energy Efficiency = Output Energy / Stored Energy

(Usable) Output Energy = Energy Efficiency x Stored Energy

The energy calculated with this formula is the usable energy of the power bank, that is, the energy that we will have available to use to recharge our devices.

If we analyze this formula, the only element we don’t know is the energy efficiency of the power bank.

This data must be established by us and, you may wonder, what value should I use?

Based on our experience, after analyzing a large number of models, we recommend using an efficiency of 85% (0.85):

There are power banks that have an efficiency higher than 90% as there are also those that have it below 80%, but if our power bank is of a good enough quality, its discharge efficiency will be around 85%

Note that this efficiency may be slightly reduced when working with fast charging protocols.

We have already seen how to calculate the usable energy of a power bank, if we want to know what is its real capacity at the output port for a given charging voltage, we simply have to express the above equation in terms of capacity and voltage:

Output Energy = Efficiency x Stored Energy

Output Capacity (mAh) x Charge Voltage (V) = Efficiency x Battery Capacity (mAh) x Nominal Battery Voltage (V)

Next, we solve our variable which would be the actual capacity at the output port and finally we get the general formula:

Output Capacity (mAh) = Efficiency x [Battery capacity (mAh) x Battery voltage (V)] / Charging voltage (V)

This formula is valid for any charging voltage if, for example, we want to calculate the real capacity at the output port of a power bank for a charging voltage of 5V we would apply the following formula:

Actual Output Capacity (5V) = 0.85 x [Battery capacity (mAh) x Battery voltage (V)] / 5V

In case you indicate the power bank capacity in energy terms (watt-hours Wh) you can use the following formula:

Actual Output Capacity (5V) = (0.85 x Stored Energy (Wh) / 5V) x 1000

Finally, we are going to apply these formulas with our power bank:

We have to remember that this model has an internal battery of 10000 mAh capacity and 3.85V voltage and we want to know what is its usable energy and its capacity at the output port for a standard charging voltage of 5V.

Let’s start by calculating the usable/output energy of the power bank assuming it has an energy efficiency of 85%:

Output Energy = Efficiency x Stored Energy = 0.85 x (10000 mAh x 3.85 V) = 32725 mWh / 1000 = 32.725 Wh

This power bank stores 38.5 watt-hours (Wh) of energy and is capable of supplying 85% of that energy, therefore, its usable energy is 32725 mWh or 32.725 Wh.

If we want to know what is the capacity at the output port for a voltage of 5V:

Actual Output Capacity (5V) = 0.85 x (10000 mAh x 3.85V) / 5V = 32725 mWh / 5V = 6545 mAh

As we can see this 10000 mAh power bank has a capacity of 6545 mAh at its output port for a voltage of 5V.

Furthermore, we check that the energy stored in the power bank (38500 mWh) does not match the energy supplied at the output port (32725 mWh) because part of it is lost as heat:

10000 mAh x 3.85V = 38500 mWh ≠ 32725 mWh = 6545 mAh x 5V

The remaining energy (38500 – 32725 = 5775 mWh) has been lost during the voltage conversion process (from 3.85V to 5V).

### To sum it up

In this section we have learned:

- That the energy at the output port of a power bank is known as usable energy and is ALWAYS going to be less than the energy stored in its battery.
- That the usable energy of a power bank will depend on the quality of its components (battery condition and efficiency of the electronic circuit).
- That the energy efficiency of a power bank is the ratio between the energy supplied at its output port and the energy stored in its battery.
- How to calculate the usable energy (theoretically) and the real capacity at the output port of a power bank knowing its specifications and assuming an energy efficiency of 85% when its battery is completely discharged.
- Stored Energy (Wh) = [Battery Capacity (mAh) x Battery Voltage (V)] / 1000
- Energy Efficiency (%) = [Output Energy (Wh) / Stored Energy (Wh)] x 100
- Output (or Usable) Energy (Wh) = Stored Energy (Wh) x 0.85
- Actual Output Capacity (mAh) = [Output Energy (Wh) / Charging Voltage (V)] x 1000

We applied the formulas with the data of the power bank used as an example in this section assuming it has an energy efficiency of 85%:

- Internal Battery Capacity of 10000mAh and nominal voltage of 3.85V.
- Discharge Energy Efficiency of 85%.
- Stored Energy (Wh) = (10000mAh x 3.85V) / 1000 = 38.5 Wh
- Usable Energy (Wh) = 38.5Wh x 0.85 = 32.725 Wh
- Actual Output Capacity at 5V (mAh) = (32.725 Wh / 5V) x 1000 = 6545 mAh

## How to measure the actual output capacity of a Power bank?

So far, we have seen some formulas that allow us to know what would be the usable energy and the real capacity of any power bank before buying it.

These formulas are based on the assumption that a generic power bank has an energy efficiency of at least 85% when fully discharged.

However, as we will see below, energy efficiency may vary from one power bank to another.

### Comparison of real vs. theoretical data

If we have already purchased a power bank and we want to know its real capacity, usable energy, and energy efficiency, it would be necessary to discharge it completely (from 100% to 0%) by connecting to an output USB port and to an electronic load at a constant voltage (V) and current (A) and use a multimeter to measure the total energy provided.

Let’s discharge our Ugreen power bank with a 10W electronic load (5V/2A) and compare the data obtained by the multimeter with the results of the formulas presented in the previous section:

Discharge Test | Stored Energy | Output Energy | Efficiency | Output Capacity |

10W (5V-2A) | 38.5 Wh | 35 Wh | 90.78% | 6769 mAh |

Theoretical (formulas) | 38.5 Wh | 32.725 Wh | 85% | 6545 mAh |

We see that the real and theoretical data are quite similar; even for this model, we obtain better results than predicted by the formulas.

For the theoretical calculation of the usable energy and real capacity of a power bank we can use another value of energy efficiency, for example, 80% or 90%, however, we consider that 85% is a valid average value for pretty much every power bank.

Although it is not very common to find in the specifications of a power bank information about the actual capacity at the output port, some manufacturers are beginning to include this information.

An example of this is the PB178 model from Ugreen:

This indicates that the manufacturer guarantees that a power bank of this model, with a battery capacity of 10000 mAh (38.5 Wh), can supply at least 6000 mAh (30 Wh) through one or more USB output ports when a charge of 15W (5V/3A) is demanded.

over, in this case, the 15W matches the total power that this model can supply (Total Output: 5V-3A).

Out of curiosity, we wanted to perform this same test with our power bank and confirmed that the guaranteed power (30Wh) is supplied:

Discharge Test | Stored Energy | Output Energy | Efficiency | Output Capacity |

Ugreen | 38.5 Wh | 30 Wh | 77.92% | 6000 mAh |

PowerBank20 | 38.5 Wh | 33.62 Wh | 87.32% | 6580 mAh |

As an additional note, you should know that the energy efficiency of a power bank also varies according to the type of discharge performed, i.e., the more current demanded (3A vs. 2A) the more energy will be lost as heat.

### real-world examples: The PowerBank20 project

In order to recommend the best power banks on the market, one of the tests we perform in PowerBank20 is the analysis of the energy efficiency of the power bank when it is completely discharged.

In the following table you can see some of the data we recorded in this test for models analyzed on our website of well-known brands in the market:

BrandModelCell TypeBattery Capacity (mAh)Battery Voltage (V)Input Energy (Wh)USB Output PortOutput Capacity 5V (mAh)Output Energy (Wh)Efficiency (%)If you are curious about all the data for each power bank analyzed you can visit this section.

### Conclusions

Before buying a power bank:

- The usable energy and actual output capacity can be estimated by knowing only their specifications and establishing a theoretical energy efficiency of 85%.
- Once we know the usable energy of the power bank we can estimate the number of charges it could perform on a cell phone.

## How to calculate the number of charges you can get from a Power bank

To calculate the number of charges that a power bank can deliver to a device we need to know:

The usable energy of a power bank is the energy available at its USB output port for transferring to a device.

To calculate it, it is necessary to know the energy stored in the power bank’s battery and its energy efficiency when discharged (recharging the device) at a given voltage.

Power Bank Usable Energy = (Stored Energy x Efficiency) / 100

Remember that the energy efficiency of a power bank will depend on the quality of the model and the type of charging performed on the device. However, as a guideline value, we recommend using an efficiency of 85%.

The recharge energy of a device is the energy required by its internal battery for a full recharge (from 0% to 100%).

To calculate it, you need to know the energy stored in the device’s battery as well as its recharge energy efficiency ( including the charging cable ):

Recharging energy of a device = (Stored Energy / Efficiency) x 100

The energy stored in a device can be found by checking the specifications in the user guide or googling ‘mah (or wh) device name’.

On the other hand, each device will have its own energy efficiency when recharged, with a value between 80 and 90%, logically, it will depend on many factors:

- Quality and state of conservation of the charging circuit.
- Charging cable: length, section, and state of conservation.
- Condition of the device’s battery itself.

However, as with a power bank, we recommend using 85% as a guideline value.

Once we know this data, we simply apply the following formula to obtain the number of charges:

Number of Charges = Power Bank Usable Energy / Recharging energy of a device

Remember, this is a general formula, and it works for any device that can be recharged with a power bank (cell phone, tablet, smartwatch…).

On the other hand, its result, logically, is not 100% accurate but it helps us to have an idea of how many approximate charges can the power bank that we are thinking of buying to charge our devices provide.

### Example: How many charges are 10000 mAh?

Here, we will estimate the number of charges that we would have on our Bq Aquaris X2 Pro cell phone, which has a 3100mAh battery, assuming that we want to buy the 10000 mAh **power bank** from Ugreen.

Subsequently, we will compare the result with the actual data obtained from the measurements once we have purchased the power bank.

The formula for estimating the number of charges on the Bq Aquaris X2 Pro cell phone using the Ugreen power bank is as follows:

Number of charges = Power Bank Usable Energy / Recharging energy of a device

The following table shows the specifications of both devices:

Specs | Ugreen PB178 Power Bank | Bq Aquaris X2 Pro Smartphone |

Battery Capacity | 10000 mAh | 3100 mAh |

Battery Voltage | 3.85V | 3.85V |

Energy Stored | 38500 mWh = 38.5 Wh | 11935 mWh ~ 12 Wh |

Let’s calculate the usable energy of the Ugreen power bank assuming it is capable of supplying 85% (0.85) of its stored energy (38.5 Wh):

Power Bank Usable Energy = 10000 mAh x 3.85 V x 0.85 = 32725 mWh ~ 33 Wh

Next, we calculate how much energy our cell phone would need to recharge its battery assuming that the recharging process (cable, voltage conversion…) has an efficiency of 85% (0.85):

Recharging energy of a device = (3100 mAh x 3,85 V) / 0.85 = 14041 mWh ~ 14 Wh

We can see that the battery of the Bq Aquaris X2 Pro needs to receive approximately 2000 mWh extra energy (14000 – 12000 mWh) to fully recharge its capacity of 12 Wh.

Finally, we calculate the estimated number of charges:

Number of charges = 33 Wh / 14 Wh = 2.36 charges

Therefore, we know that if we buy the Ugreen power bank of 10000 mAh capacity we would have 2 full charges (from 0% to 100%) on our Bq Aquaris X2 Pro mobile and, in addition, we would still have energy for a third partial charge (from 0% to 36%).

For the above calculation, we have seen that an efficiency of 85% has been used both for discharging the power bank and for recharging the device.

While the energy efficiency in recharging the device can be checked if you have the necessary measuring equipment, we do not know the efficiency in discharging a power **bank** before buying it.

For this reason, we say that the calculated number of charges is a guideline but valid enough for anyone who is interested in buying a power bank and wants to have an approximate idea of the number of charges that would have on your device without making the mistake of dividing the capacity of the power bank by the capacity of the device:

Number of charges = 10000 / 3100 = 3.22

However, for our more curious readers, let’s check the actual number of charges we would have on the mobile after purchasing the Ugreen **power** bank.

### Data validation

The following tables show the results obtained from the tests of recharging the mobile and discharging the power bank both for standard charging (the usual charge for any device with a USB charging port) and for Quick Charge 3.0 fast charging and Power Delivery (this mobile is compatible with both protocols).

We also verified that the average efficiency obtained in both tests differs from the 85% established in the theoretical formulas.

Bq Aquaris X2 Pro Smartphone

Type of Charge | Charging Cable | Stored Energy | Recharging energy of a device | Efficiency |

Standard (5V) | USB-A to USB-C | 11.94 Wh | 14.63 Wh | 81.61 % |

Quick Charge 3.0 | USB-A to USB-C | 11.94 Wh | 15.20 Wh | 78.55% |

Power Delivery | USB-C to USB-C | 11.94 Wh | 14.70 Wh | 81.22 % |

Average | 11.94 Wh | 14.84 Wh | 80.46 % |

- We note that this cell phone has an average recharge efficiency of 80% with a required power supply of approximately 15Wh.
- The charging cable is taken into consideration for the measurement of the recharging energy of the device.

Ugreen PB178 Power Bank

Discharge Type | USB Port | Electronic Load | Energy Stored | Output Energy (usable) | Efficiency |

Standard (5V) | USB-A | 10W | 38.5 Wh | 34.95 Wh | 90.78 % |

Quick Charge 3.0 | USB-A | 14W | 38.5 Wh | 34.04 Wh | 88.42 % |

Power Delivery |
USB-C | 14W | 38.5 Wh | 34.05 Wh | 88.44% |

Average | 38.5 Wh | 34.35 Wh | 89.22 % |

- We observed that this model is capable of supplying more energy (90%) than what we established for the theoretical calculation (85%).
- To measure the energy that a power bank can supply through its output USB port we perform a complete discharge by connecting an electronic load at constant power. Taking into account the charging power of a cell phone we performed our tests with 10 and 14W for standard and fast charging respectively.

With these data we calculate the actual number of charges by applying the above formula:

Type of Charge | Power Bank Usable Energy | Recharging Energy of a Device | Number of Charges |

Standard (5V) | 34.95 Wh | 14.63 Wh | 2.39 |

Quick Charge 3.0 | 34.04 Wh | 15.20 Wh | 2.24 |

Power Delivery | 34.05 Wh | 14.70 Wh | 2.32 |

Average | 34.35 Wh | 14.84 Wh | 2.31 |

## Coolreall Power bank **20000mAh** : une batterie externe pour recharger tous vos appareils rapidement

Les batteries de secours sont devenues très populaires depuis quelques années. Ces accessoires, aussi appelés power bank, s’avèrent être indispensables puisque nous ne pouvons plus nous passer de nos smartphones et nos tablettes alors que leurs batteries tombent en panne rapidement dans la majorité des cas. Le Coolreall Power bank fait aujourd’hui partie des modèles les plus en vue. Ce modèle allie puissance, rapidité de charge, sécurité et performances. Capable de recharger jusqu’à trois appareils en même temps, il vous dépannera à tout moment et gardera vos appareils en marche même lorsque vous vous trouvez dans une zone sans électricité ou sans prise de secteur.

Coolreall **Power** bank avis

Points négatifs La charge devient moins efficace lorsque __trois appareils__ sont connectés simultanément sur le Coolreall Power bank. Pour obtenir un chargement complet et rapide, il est donc conseillé de brancher tout au plus deux appareils. Au niveau du design, ce modèle dispose d’un corps et d’une finition assez peu recherchés. Sa conception est très basique et ne séduit pas toujours. Si vous recherchez un modèle avec un meilleur design, choisissez la batterie externe Vinsic **20000mah**.

Points positifs Le **Coolreall** Power bank est à peine plus grand qu’un smartphone. Il se transporte donc très facilement en prenant très peu de place dans un sac ou même dans une poche. En plus, il pèse beaucoup moins lourd que d’autres modèles de la même gamme. Dans une poche, il paraît donc beaucoup plus encombrant. Cette batterie externe présente aussi l’avantage d’être très accessible. Elle coûte seulement 21,59 €. De ce fait, il fait incontestablement partie des modèles de __20 000 mAh__ les moins chers du marché. Sa qualité n’est pourtant pas en reste. Cette batterie présente une durée de vie d’au moins 5 ans.

En quelques mots Malgré une restriction dans le nombre d’appareils rechargeables, le **Coolreall** Power bank est un bon chargeur externe. Il parvient à charger correctement et rapidement vos appareils et vous dépanne en temps voulu. Son rapport qualité/prix constitue en outre son plus grand point fort. Vous pouvez comparer ce modèle avec le Poweradd Pilot X7 20 000 mAh qui coûte beaucoup moins cher.

## Caractéristiques

Marque : Coolreall Type : power bank, **batterie** externe Nombre de ports USB : 3 Capacité : 20 000 mAh Entrée : 5 V, 2.0 A Sortie : 5 V, 3.0 A Compatibilité : tous les appareils fonctionnant sous iOS et Android, mais aussi ceux qui disposent d’un port USB (MP3/MP4), GPS… Couleur : noir Contenu du pack : 1 batterie externe, 1 câble USB de 20 cm, 1 manuel d’utilisation

## Faites des économies substantielles avec le **Coolreall** Power bank

Comme pour tous les produits, l’achat d’une batterie externe se fait en considérant le prix. Le Coolreall Power bank présente un très bon rapport qualité/prix. Vous aurez besoin de moins de 22 € pour l’acheter. Malgré ce prix très accessible, le modèle présente une qualité satisfaisante autant au niveau des performances que des matériaux utilisés pour sa fabrication. Par ailleurs, la marque Coolreall propose un excellent service après-vente. Bien qu’aucune garantie ne soit proposée pour ce produit, vous pourriez bénéficier de prestations gratuites en après l’achat.

## Un système de sécurité performant

La marque Coolreall est consciente de la sécurité lors du chargement de vos batteries. De nombreuses instabilités peuvent endommager la batterie et impacter son autonomie et sa longévité. Pour prévenir les surcharges, le Coolreall Power bank s’arrête automatiquement lorsque l’appareil branché a atteint son niveau de charge maximal. La batterie externe dispose aussi d’un système intelligent qui détecte automatiquement la puissance à laquelle l’appareil doit être chargé. Lorsque trois appareils sont chargés simultanément, le courant en sortie atteint 3 A.

Vous êtes dans le doute ? Consultez le top 5 ainsi que notre guide des meilleurs batteries externes.

### Conclusion

Le **Coolreall** Power bank est un chargeur externe performant. Sans être le meilleur modèle du marché, il peut se vanter de pouvoir charger jusqu’à trois appareils en même temps. Compatible avec un vaste choix de smartphones et d’appareils que vous utilisez au quotidien. Avec ses nombreux avantages, ce modèle sera votre accessoire préféré pour éviter les pannes de batterie.

## How To Reset Power Bank of Any Brand-2 Methods

A power bank is a great innovation as it allows you to charge your phone anywhere and anytime. This guide will tell you how can you reset a power bank.

Generally, you need to reset the power bank when it is posing charging problems. For example, the power bank is not charging itself or not charging the phone.

over, the power bank is draining fast or frozen. All these problems can be solved by resetting your device if the issue is not hardware-related.

But, sometimes, it happens due to failed battery or defective hardware. So, in this case, the power bank needs to be repaired or even replaced.

There are various brands of power banks in the market. Samsung and Anker are one of the most popular power banks.

Similarly, Xiao Mi, Romoss, Cygnett, RavPower, Imuto, Iniu, and Belkin are some other brands.

- The Anker Advantage: Join the 50 million powered by our.
- Ultra-High Capacity: Weighs as little as a can of soup (12.5.

There are two basic reset methods that can be applied to all these power banks. If one does not work, you can apply the second method.

## Power Bank Maintenance Tips

Since a power bank is an electronic device, it is vulnerable to temporary faults.

Many factors can affect the health of your devices such as weather changes, electric shock, water, heat, and even the charging cable.

- Always use the USB cable provided with your power bank. Avoid purchasing third-party or cheap cables.
- Because if you charge your device using an incompatible charging cable, it will not charge fully.
- While your power bank is being charged, avoid charging your phone from it.
- You should charge your phone when the power bank is full and you have removed the power supply.
- Protect your device from direct heat and sunlight. Keep it away from a heat source or an electromagnetic device.
- Use your power bank to charge the devices that are recommended. Charging an incompatible device will affect the battery.
- Keep your charging bank neat and clean. Regularly clean its ports with a clean cloth and new toothbrush.
- If you use the device irregularly, do not forget to charge it every 3 months.
- Avoid putting pressure on your device like some users place bundles of books or other things on their power bank.
- Observe the light indicators while your device is connected to the power supply. Do not overcharge or undercharge your device.
- Avoid draining out the battery fully. Lithium-ion batteries have an automatic protective mechanism. So, they can damage due to insufficient charge.
- This will also decrease the life of your device and it will be difficult to charge a fully drained battery.
- Also, avoid using your phone while it is charging through the power
**bank**. Because this habit can damage both devices. - 【2023 Upgraded USB-C Output】Two 10000mAh battery packs.
- 【Dual Output Input】Each also has 2 USB output ports.

## FAQs: Frequently Asked Questions

### Can a power bank explode? Why?

A power bank explodes if it has low-quality power cells. If you overcharge it, the cell melts and causes exploding.

However, even if you own a high-quality power bank, avoid overcharging it.

Power bank explosion not only damages the device or phone but can also harm the user.

### What is the average life of a **power** bank?

According to an estimate, a power bank lasts between 3-4 hours. over, it can remain charged for around 3-6 months.

However, if you follow the guidelines given in this article, you can extend the lifespan of your power bank.

### How many times I can recharge my power bank?

Using the power bank regularly will decrease its charging cycles. If you use it occasionally, you can get more charging cycles.

Most strong power banks last up to 1,000 charging cycles. While a normal and small power bank can last 200-300 cycles.

### Can a power bank damage my phone?

Normally, the power bank does not damage your phone. Nevertheless, if you overcharge your phone, it will definitely damage it.

over, using the phone during charging can also harm your device. Use the power bank only when you do not have access to electricity.

Under normal conditions, charge your phone directly through the power supply outlet.

### Should I charge a brand new power bank before using it?

Most manufacturers recommend charging your device before first-time use. There are various types of power banks depending on the battery power and size.

Therefore, the charging time varies, ideally you should follow the instructions given in the manual. Generally, a brand new power bank takes 1-2 hours to fully charge.

## Final Words

We have included mostly asked questions in this guide. However, if you want to ask any other things, contact us without any hesitation.

In addition, this guide has also included some very important tips to keep your device healthy. You must follow them accordingly.

We have told you two methods to reset your power bank. You can try both with your particular device as they are common for all brands.

Last update on 2023-06-04 / Affiliate links / Images from Amazon Product Advertising API

Hi, I’m Memona Aman, Editor of Speakersmag.com. I am naturally inclined towards modern technical gadgets. I love to research on speakers and soundbars. I write articles on this blog to share my latest knowledge. I am happy to assist you in your search for the best audio devices. Read more about me

## Test Coolreall PB-K8 20000 mAh : une star bien trop capricieuse

Le petit monde des batteries externes n’étant pas aussi attractif que celui des smartphones, les grands noms du secteur sont assez rares. Pour trouver chaussure à leur pied, de nombreux consommateurs ont recours à un moyen pragmatique : taper batterie externe sur le moteur de recherche d’un site marchand bien connu. Et l’une des stars en la matière n’est d’autre que la Coolreall 20 000 mAh, que nous testons ici.

## Présentation

Parmi les marques relativement connues telles que Anker, Aukey ou Mophie, le nom Coolreall détonne un peu. Pas même un site Internet à proprement parler : la marque est quasi inconnue du grand public ; pourtant, elle squatte le classement des batteries externes les plus vendues sur Amazon. Nous avons donc cherché à savoir ce que valait cette star méconnue qu’est la **Coolreall** 20 000 mAh, nom de code K8.

La batterie massive prétend embarquer 20 000 mAh de capacité théorique dans son corps imposant et est équipée de 3 ports USB-A standards. Elle est fournie avec une housse de rangement et un câble micro-USB pour la recharge, et coûte autour de 20 €.

## Ergonomie

Exception faite de l’ovni qu’est l’Anker PowerCore 10 000 mAh, la plupart des batteries embarquant 10 000 mAh ou plus se rangent résolument dans la catégorie des belles briques bien encombrantes. Alors avec ses 20 000 mAh, la K8 est forcément une bête plutôt imposante. Ses mensurations de 16 cm de long, 8 de large et 2 d’épaisseur pour un poids de 408 g en feront un accessoire que l’on préférera transporter dans un sac plutôt que dans une poche de pantalon (ou alors avec une bonne ceinture). C’est le prix à payer pour une capacité aussi importante.

La construction en elle-même est assez banale : des plaques de plastique mat légèrement incurvé sur les faces inférieure et supérieure, liées par un bandeau en plastique glossy. On est loin de ce que peut proposer Mophie, par exemple, mais globalement, le choix des matériaux ne laisse pas trop à désirer. On remarquera tout de même qu’à certains endroits la **batterie** sonne plutôt creux, preuve qu’un petit travail d’optimisation de l’encombrement aurait pu être fait.

Là où la Coolreall K8 loupe vraiment le coche côté ergonomie, ce n’est pas sur sa construction ou sur sa prise en main, mais sur l’intégration des ports USB, quels qu’ils soient. Les 3 ports de chargement sur la tranche sont légèrement trop enfoncés dans la coque de la batterie, rendant le simple acte de brancher un appareil un peu laborieux à l’aveugle. Plus pénible encore, le port micro-USB servant pour la recharge est lui aussi niché bien trop loin à l’intérieur de l’appareil.

À moins donc d’avoir un câble avec un embout micro-USB particulièrement long, il faudra veiller à ne surtout pas faire bouger la batterie sous peine que le contact — donc la charge — ne se fasse plus. Une **batterie** externe délicate à charger, c’est un comble.

## Autonomie

Si, malgré les défis que vous pose la Coolreall, vous parvenez tout de même à la charger complètement et décidez de l’emporter pour vos longues journées loin des prises électriques, à quoi pouvez-vous vous attendre côté capacité ? Eh bien, dans les faits, la **batterie** fournit environ 20 % de moins que la capacité annoncée, soit 16 000 mAh sur 20 000 en 3,7 V et 12 640 mAh sur 15 640 en 4,7 V (intensité correspondant à la recharge d’un smartphone). À ce compte, vous serez mieux servis par une X-Moove Powergo Flash qui, malgré sa capacité annoncée inférieure, délivre au bout du compte plus de jus que cette Coolreall.

La K8 pourra tout de même recharger un iPhone 6S plus de 7 fois, un Galaxy S6 5 fois, un LG G4 un peu plus de 4 fois et un iPad Air 2 1,7 fois. En revanche, il ne faudra pas compter sur la charge rapide, puisque nous n’avons jamais relevé une charge dépassant les 5 V / 1,6 A (soit 8 W) lors de nos tests. Que l’accessoire soit branché à un Galaxy S6 edge, un LG G6 ou à un iPhone 7 Plus. Bref, il ne faudra pas être trop pressé si vous voulez récupérer quelques pourcents.

Enfin, pourvu que vous n’effleuriez pas la batterie et ne fassiez pas tomber le connecteur micro-USB de son logement, la charge complète de la bête prendra environ une douzaine d’heures.