1 Voltage Unit Volt V

Voltage is the potential difference between the two ends of the battery, which can be compared to the water pressure at the two ends of a water pipe.

2 Current Unit Ampere A

The directional movement of charge forms a current. The current can be the movement of electrons in a conductor such as a wire, or the movement of ions in the electrolyte 

in the positive and negative electrodes.

3 Capacity Unit Ampere-hour Ah

The amount of electricity stored in the battery is amperes per hour, which means the amount of electricity that the battery can continuously charge or discharge in 1 hour. 

For example, a 20Ah battery means that it can continuously discharge for 1 hour at a current of 20A, and it can continuously discharge for 2 hours at a current of 10A.

4 Nominal voltage

The appropriate voltage approximation marked by the manufacturer has the longest continuous discharge time. For example, the working voltage of ternary 

lithium battery is between 2.8V and 4.2V, and the nominal voltage is 3.7V. The working voltage of lithium iron phosphate is between 2.5V and 3.65V, and the nominal voltage

 is 3.2V. When we design the battery pack, we calculate the voltage based on the nominal voltage.

5 Nominal capacity

The capacity of the battery cell marked by the 

manufacturer for storing electrical energy, generally in mAh or Ah (1000mAh=1Ah). The nominal capacity is an important basis for calculating the capacity and 

ensuring the consistency of the battery pack design. 

6 Rate C 

The ratio of the current to the nominal capacity of the battery during charging and discharging. This is a very important 

parameter for lithium batteries. The maximum charge and discharge time and charge and discharge current of the battery can be calculated based on the rate. 

For example, for a 2Ah5C battery, 5C means that the fastest 2Ah of electricity can be discharged in 0.2 hours, that is, the maximum continuous discharge current of the battery 

can reach 10A. The fastest discharge time formula: 1÷5C=0.2 hours

The maximum discharge current formula: 2Ah×5C＝10A).

The battery can also be compared to a bucket. 1C represents a faucet. It takes exactly 1 hour to drain the water in the bucket by fully opening the faucet. 5C represents that the 

bucket has 4 more faucets of the same size as before. When the faucet is fully opened, 5C is 5 times the flow rate of 1C. It only takes one-fifth of 1C to drain a bucket of water. 

The higher the rate, the more expensive the battery cell. You must choose the appropriate rate battery cell according to the usage scenario. For example, drones, model airplanes, 

power tools, etc. have restrictions on volume and weight, but the motor power is large and the continuous discharge current is large. It is impossible to make the battery voltage

 and capacity large enough. At this time, it can be compensated by high-rate batteries, generally more than 10C. Low-speed vehicles

Generally, the voltage and capacity are higher, and 3C or 5C batteries are basically sufficient. The higher the rate, the smaller the internal resistance.

7 Internal resistance Unit ohm Ω

The resistance value inside the battery is different from the concept of ordinary resistance. It cannot be measured with an ordinary multimeter and

 requires a professional internal resistance meter. This is also a very important parameter of lithium batteries. It is an important basis for

 assembling lithium batteries and grouping. It is also an important indicator for judging the quality of batteries during maintenance. 

The quality of batteries can also be roughly judged based on the internal resistance. 

The lower the internal resistance, the better. Domestic 18650 batteries are generally around 20 milliohms, 1 ohm = 1000 milliohms. 

The internal resistance is zero or infinite, indicating that the battery is damaged.

8 Consistency

The convergence of important parameters of all cells in the same lithium battery pack mainly refers to the same internal resistance, voltage, capacity, state 

of charge SOC and other parameters of the same group of cells. The smaller the error, the better.Generally, the voltage error does not exceed 5mv and the internal resistance does

 not exceed 3mΩ. This is crucial for the assembly and maintenance

of lithium batteries. The better the consistency, the more stable the battery pack and the longer the life. Most battery failures are caused by poor consistency.

9 Cycle life

A cycle is a cycle when the battery completes a complete charge and discharge process. After completing the number of cycles calibrated by the manufacturer, 

the remaining capacity of the lithium battery is not less than 80% of the nominal capacity. The cycle life of the lithium battery is generally 500-6000 times. 

The cycle life of different materials and manufacturers is different. The manufacturer's specification book shall prevail.

10 Depth of discharge DOD

How much battery capacity should be used during use. For example, a 20Ah battery will not be protected until the 20Ah of electricity is fully discharged, 

and its discharge depth is 100%. The protection board on the market protects the battery when it is charged to 4.2V and when it is discharged to 2.8V. 

This design has a discharge depth of 100%. This will reduce the stability and service life of the battery, but it can safely utilize all the capacity of the lithium battery. 

11 State of charge SOC 

The ratio of the remaining battery power to the total battery power. Just like the fuel gauge of a car, it indicates the current state of battery storage power. 

12 Balance 

Lithium batteries are basically composed of N series-parallel cells.

The SOC states of multiple series-connected cells are basically the same. Balance is achieved by actively adjusting the voltage of each series of cells to be as consistent as possible. 

13 Parallel   P Multiple identical cells are connected with positive electrodes and negative electrodes, and multiple cells are connected in parallel with increased capacity and unchanged voltage.

 If 5 3.7V 2Ah batteries are connected in parallel, the voltage remains unchanged and is still 3.7V. The capacity after parallel connection is: 5×2Ah＝10Ah

14 Series connection S

The positive pole of multiple identical batteries is connected to the negative pole of another battery. The voltage of multiple batteries in series increases and the capacity 

remains unchanged. If 5 3.7V 2Ah batteries are connected in series, the capacity remains unchanged and is still 2Ah. The voltage after series connection is: 5×3.7V＝18.5V

Note: Whether in parallel or series connection, consistency must be ensured.

15 Short circuit

The current does not pass through the external electrical appliance directly through the internal or external wires of the battery to form a loop between the positive and

 negative electrodes, so that all the current flows back to the battery. This situation is called a short circuit.

The internal short circuit mainly includes forced internal short circuit caused by metal objects piercing the battery shell, and the battery cell expands and deforms after 

overcharging, resulting in a short circuit between the positive and negative materials inside the battery cell. External short circuits mainly include 

unreasonable layout of protection board wiring, extrusion causing wiring insulation rubber to fall off and short circuit. Inadequate insulation measures during

 cell arrangement cause short circuits between cell shell and bus, between shell and shell, etc. During short circuit, the current will be very large, 

which will lead to air crash consequences. Most accidents of lithium batteries are caused by short circuits, so the hidden dangers of short circuits must be eliminated 

in actual operation. 16 Aging The aging of lithium battery PACK does not refer to the decline of lithium battery performance, 

but refers to the test of various performance indicators of lithium battery packs before the finished lithium battery is packaged and shipped during the PACK process.

 It can be performed with a professional aging cabinet, or with a charge and discharge instrument to charge and discharge the battery.