1. Battery voltage (V)

Open circuit voltage (OCV)

Lithium battery is not connected to the external circuit or load voltage, generally with a multimeter can be tested.

Operating voltage (WV)

The potential difference between the positive and negative terminals of the battery under external load, i.e. when a current flows through the battery in the circuit. When the battery is working, there will be current flowing through the battery. Because of the internal resistance and load resistance of the battery itself, the operating voltage of the battery is always lower than the open-circuit voltage.

Discharge cut-off voltage (DCV) :

Refers to the battery in the case of electric energy, discharge to reach the set voltage, generally set voltage is 3.0V or above, overdischarge will have irreversible impact on the battery.

2.Battery capacity (Ah or mAh)

Battery capacity refers to the amount of electricity released by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.), which is one of the important indicators of battery electrical performance. It is expressed in C and expressed in Ah (ampere hours) or mAh (mah hours). Battery capacity (Ah) = Current (A) x discharge time (h).

1) Rated capacity

That is, the capacity indicated on the battery packaging is the lowest capacity released under standard conditions according to the standards promulgated by the state or relevant departments.

2) Theoretical capacity

The design is based on the mass of the active substance by Faraday's law calculation of the theoretical value.

3) Actual capacity

According to the actual situation of the battery, under a certain charge-discharge system released battery capacity. It is related to the condition of the battery itself, such as SOC, SOH and so on, as well as the charge and discharge system.

3. Battery internal resistance (mΩ)

The internal resistance of a battery is the resistance to flow through a current. Battery internal resistance is mainly affected by battery materials, production technology, battery structure and other factors. It includes ohmic internal resistance and polarized internal resistance:

Ohmic internal resistance: depends on the composition of electrode material, electrolyte, diaphragm resistance, contact resistance between materials, and contact resistance with the housing. When a battery is discharged, the Ohm resistance obeys Ohm's law.

Polarization internal resistance: it is mainly the electric resistance caused by the electrochemical polarization and the concentration difference polarization generated when the battery flows through the electric current. The polarization resistance increases with the current density, but is not linear, and often increases linearly with the logarithm of the current density.

The internal resistance of a battery is not a constant and changes over time during discharge because the composition of the active substance, electrolyte concentration and temperature are constantly changing.

4. Charge Cycle life

A secondary battery is called a cycle or a cycle. After repeated charging and discharging, the capacity of the battery gradually decreases. Generally, lithium batteries are required to charge and discharge under standard conditions. When the battery capacity is reduced to 80%, the number of cycles the battery experiences is the cycle life.

Influencing factor:

Improper use of batteries, battery materials, electrolyte composition and concentration, charge-discharge ratio, discharge depth (DOD%), temperature, and production process all affect the cycle life of batteries.

5. Energy density (Wh/Kg)

Volume specific energy or mass specific energy refers to the energy released per unit volume or mass, usually expressed as volume energy density (Wh/L) or.

Calculation formula:

Volume Energy density (Wh/L) = Battery capacity (Ah) x average discharge platform (V)/ battery volume (L)

Mass Energy density (Wh/kg) = Battery capacity (Ah) x Average discharge platform (V)/ Battery weight (Kg)

6. Battery charging and discharging depth (SOC, DOD)

Charge depth: The ratio of charge to nominal capacity, usually expressed as SOC.

Discharge depth: Discharge depth is the ratio of discharge capacity to nominal capacity. It is usually denoted by DOD.

For example, if the capacity of a 20Ah battery is discharged, the capacity becomes 4Ah, which can be called 80%DOD. If the capacity of the battery after charging is 10Ah, the charging depth of 50%SOC can be used.

7. Charge and discharge ratio (A)

Discharge rate: the current value required to discharge its rated capacity within a specified time, which is numerically equal to the multiple of the rated capacity of the battery. For example, if the discharge rate is 2C, the battery discharge current is 2 x the capacity of the battery (unit: A).

Charge ratio: The rate at which the battery is charged, which is equal to the rated capacity of the battery.

Classification of discharge rate:

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8. Over discharge

Battery in the discharge process, exceed the battery discharge termination voltage value, but also continue to discharge, it may cause the battery internal pressure rise, positive and negative active material reversible damage, so that the capacity of the battery significantly reduced.

9. Over charge

When the battery is charged, if it continues to charge after it has reached the full state, it may lead to increased internal pressure, battery deformation, night leakage and other conditions, and the performance of the battery will be significantly reduced and damaged, or even dangerous explosion.

10. Load capacity

When the positive and negative ends of the battery are connected to the electrical appliance, the output power that drives the electrical appliance to work is the load capacity of the battery.

11.Battery formation

After the battery is assembled and injected, the positive and negative electrode active substances are activated through certain charging and discharging ways to improve the battery's charge-discharge performance, self-discharge, storage and other comprehensive performance. Only after the battery has been formed can its true performance be realized. At the same time, the separation process in the formation process can improve the consistency of the battery pack and improve the performance of the final battery pack.

12. Battery capacity

In the process of battery production, due to the process and material itself, the actual capacity of the battery is impossible to be completely consistent, through a certain charge-discharge system detection, and the battery capacity classification process is called capacity separation.

13. Consistent battery pack

A battery pack is composed of multiple cells connected in series and parallel. The overall performance and life of a battery pack depends on the poor performance of one cell, which requires high consistency of performance of each cell in the battery pack.

For example, batteries of the same batch and model are screened by the consistency of voltage, internal resistance, capacity, and even charge-discharge curves to improve the consistency of the battery pack.