Preface
Recently, the charging head network in the dismantling of the new 25000mAh 145W fast charging mobile power supply found that it is equipped with BAK N21700CG-50 cells, a single 5000mAh, a total of five components, BAK Battery Co., Ltd. was established in 2001, is a collection of lithium-ion battery cell research and development, production, Sales as one of the high-tech enterprises, the daily output of lithium cells reached 1.5 million, one of the world's largest lithium battery manufacturers, the company's products are mainly lithium-ion secondary rechargeable batteries, including mobile phone batteries, laptop batteries, digital batteries, power batteries, etc., let's take a look at the performance of this cell.
Appearance introduction
As usual, let's take a look at the appearance of this cell first.
BAK N21700CG-50 battery cells are cylindrical design, using purple cell sleeve color, and the sleeve color can be adjusted according to requirements to meet the diverse needs of customers.
The other side of the BAK N21700CG-50 battery cell has a cell inkjet code:
"N21700CG-50 BAK A02"
Rated capacity: [email protected];
Nominal voltage: 3.6V, nominal energy: 18Wh;
AC internal resistance: ≤30mΩ.
The contact surface of the negative electrode of BAK N21700CG-50 battery cell is made of alloy metal and anodized by anodizing, which is durable and anti-corrosion.
The positive contact surface of BAK N21700CG-50 cell is still made of alloy, and the disc is connected by three solder joints.
Measured with plastic calipers, the cylindrical height of BAK N21700CG-50 cells is about 70.9mm.
Using plastic calipers, the diameter of the BAK N21700CG-50 cell column is about 21.1mm.
The BAK N21700CG-50 battery cell weighs about 67.8g.
Charge and discharge test
After looking at the appearance, let's get to the point, and the following will be charged and discharged at 0.2C, 0.5C and 1C rates.
Charge test
The charging test will perform constant current and constant voltage charging at 0.2C, 0.5C and 1C rates, and calculate the total time consumption.
0.2C charging
Draw a line chart, set the current to 1000mA, 0.2C to charge the BAK N21700CG-50 cells, and the charging cut-off voltage is 4.2V, which takes about 5 hours and 20 minutes.
0.5C charging
Draw a line diagram, set the current to 2500mA, 0.5C to charge the BAK N21700CG-50 cell, the charging cut-off voltage is 4.2V, and it takes about 2 hours and 28 minutes.
1C charging
Draw a line chart, set the current to 5000mA, 1C to charge the BAK N21700CG-50 cell, the charging cut-off voltage is 4.2V, and it takes about 1 hour and 35 minutes.
The test data is plotted as a line chart, and it takes 5 hours and 20 minutes to fully charge 0.2C, 2 hours and 28 minutes to fully charge 0.5C, and 1 hour and 35 minutes to fully charge 1C.
Discharge test
In the discharge test stage, a constant current discharge will be used to calculate the total time consumed, as well as the discharge capacity and energy values.
0.2C discharge
Draw a line chart, set the current to 1000mA, 0.2C is the discharge of BAK N21700CG-50 cells, the average voltage is 3.62V, and the cut-off voltage is 2.5V, which takes about 4 hours and 56 minutes, and the discharge capacity is 4942mAh and the discharge energy is 17.9Wh.
0.5C discharge
Draw a line chart, set the current to 2500mA, 0.5C is the discharge of BAK N21700CG-50 cells, the average voltage is 3.62V, and the cut-off voltage is 2.5V, which takes about 1 hour and 57 minutes, and the discharge capacity is 4909mAh and the discharge energy is 17.59Wh.
1C discharge
Draw a line chart, set the current to 2500mA, 0.5C is the discharge of BAK N21700CG-50 cells, the average voltage is 3.62V, and the cut-off voltage is 2.5V, which takes about 58 minutes, and the discharge capacity is 4880mAh and the energy is 17.18Wh.
Summarizing the test data into a table, it can be seen that the battery cell is discharged at three magnifications, and the shortest discharge time is 1C discharge, and the discharge time is about 58 minutes. The longest discharge time is 0.2C discharge, and the discharge time is about 4 hours and 56 minutes.
The test data is summarized into a histogram, the overall discharge energy in the discharge test is between 17.19-17.9Wh, the overall gap is not large, the highest discharge energy is 0.2C discharge gear, the discharge energy reaches 17.9Wh, close to the nominal energy, the lowest discharge energy is 1C discharge gear, discharge energy is 17.18Wh.
Let's take a look at the difference in the capacity of each gear, and plot the data into a curve graph, you can see that the 0.2C discharge gear has a discharge capacity of 4942mAh, and the lowest discharge capacity is 4880mAh at the 1C discharge gear.
Internal resistance test
In the internal resistance test part, the charging head network will use the internal resistance test instrument to test the full power internal resistance and empty power internal resistance respectively.
Summarizing the test data into a table, we can see that the internal resistance voltage of the full charge is 4.2V, the air internal resistance voltage is 2.5V, and the nominal internal resistance of the BAK N21700CG-50 cell is ≤30mΩ.
Drawing a histogram, we can see that the 4.2V full-charge internal resistance is 13.71mΩ and the 2.5V air-electric internal resistance is 15.86mΩ, both of which do not exceed the nominal internal resistance.
Temperature test
In the temperature test part, the charging head network will measure the temperature of each charge and discharge rate after 30 minutes.
Charging temperature test
0.2C charging
The BAK N21700CG-50 battery cells are charged at a rate of 0.2C for 30 minutes, and the maximum surface temperature is about 26.8°C.
0.5C charging
The BAK N21700CG-50 battery cells are charged at a rate of 0.5C for 30 minutes, and the maximum surface temperature is about 27.4°C.
1C charging
The BAK N21700CG-50 battery cells are charged at a rate of 1C for 30 minutes, and the maximum surface temperature is about 33.5°C.
Discharge temperature test
0.2C discharge
BAK N21700CG-50 cells are discharged at a rate of 0.2C for 30 minutes, and the maximum surface temperature is about 24.6°C.
0.5C discharge
BAK N21700CG-50 cells are discharged at a rate of 0.5C for 30 minutes, and the maximum surface temperature is about 27.1°C.
1C discharge
BAK N21700CG-50 cells are discharged at a rate of 1C for 30 minutes, and the maximum surface temperature is about 33.8°C.
Summary of the charging head network
This BAK N21700CG-50 cell, the charging head network was tested at 0.2C, 0.5C and 1C three rates, charging, 1C rate charging can be completed in 1 hour and 35 minutes, and the discharge part, you can see that the 0.2C rate discharge capacity is 4942mAh, and the energy released reaches 17.9Wh.
In terms of temperature, the charging temperature is in the range of 26-33 °C, and the discharge temperature is in the range of 24-33 °C, and the overall heat generation is not large.
BAK N21700CG-50 cells provide reliable and powerful power support for a wide range of applications. Whether in electric vehicles, portable devices or energy storage systems, the cell has demonstrated outstanding potential and provides a reliable power solution for the industry.