# What are the technical parameters of the battery Lithium - Ion Battery Equipment

## What are the technical parameters of the battery -Lithium - Ion Battery Equipment

1. Electromotive force

The electromotive force is the difference between the balance electrode potentials of the two electrodes. Taking lead-acid batteries as an example, E=ąż+0-ąż-0+RT/F*In(αH2SO4/αH2O).

Among them: E—electromotive force

ąż+0—positive standard electrode potential, its value is 1.690

ąż-0—negative standard electrode potential, its value is -0.356

R - universal gas constant, its value is 8.314

T - temperature, related to the temperature of the battery

F - Faraday's constant, its value is 96500

αH2SO4—the activity of sulfuric acid, which is related to the concentration of sulfuric acid

αH2O—the activity of water, which is related to the concentration of sulfuric acid

It can be seen from the above formula that the standard electromotive force of the lead-acid battery is 1.690-(-0.0.356)=2.046V, so the nominal voltage of the battery is 2V. The electromotive force of lead-acid batteries is related to temperature and sulfuric acid concentration.(Lithium - Ion Battery Equipment)

2. Rated capacity

Under the conditions specified in the design (such as temperature, discharge rate, termination voltage, etc.), the minimum capacity that the battery should be able to discharge, in ampere-hours, represented by the symbol C. The capacity is greatly affected by the discharge rate, so the discharge rate is often marked with Arabic numerals in the lower right corner of the letter C, such as C20=50, indicating that the capacity at a rate of 20 hours is 50 amp hours. The theoretical capacity of the battery can be accurately calculated according to the amount of electrode active material in the battery reaction formula and the electrochemical equivalent of the active material calculated according to Faraday's law. The actual capacity of the battery is often lower than the theoretical capacity due to the side reactions that may occur in the battery and the special needs of the design.

3. Rated voltage

The typical operating voltage of the battery at room temperature, also known as the nominal voltage. It is a reference when choosing different types of batteries. The actual operating voltage of the battery varies with different usage conditions. The open circuit voltage of a battery is equal to the difference between the balance electrode potentials of the positive and negative electrodes. It is only related to the type of electrode active material, and has nothing to do with the amount of active material. The battery voltage is essentially a DC voltage, but under some special conditions, the phase transition of the metal crystal or some phase-forming films caused by the electrode reaction will cause slight fluctuations in the voltage, which is called noise. The amplitude of the fluctuation is small but the frequency range is very wide, so it can be distinguished from the self-excited noise in the circuit.

4. Open circuit voltage

The terminal voltage of the battery in the open circuit state is called the open circuit voltage. The open circuit voltage of a battery is equal to the difference between the positive electrode potential and the negative electrode potential of the battery when the battery is open circuit (ie, when no current flows through the two poles). The open circuit voltage of the battery is represented by V on, that is, V on = ąż+-ąż-, where ąż+ and ąż- are the positive and negative electrode potentials of the battery respectively. The open circuit voltage of the battery is generally less than its electromotive force. This is because the electrode potential established by the two poles of the battery in the electrolyte solution is usually not a balanced electrode potential, but a stable electrode potential. Generally, it can be approximated that the open circuit voltage of the battery is the electromotive force of the battery.

5. Internal resistance

The internal resistance of a battery refers to the resistance to current passing through the interior of the battery. It includes ohmic internal resistance and polarization internal resistance, and polarization internal resistance includes electrochemical polarization internal resistance and concentration polarization internal resistance. Due to the existence of internal resistance, the working voltage of the battery is always less than the electromotive force or open circuit voltage of the battery. The internal resistance of the battery is not constant, and it keeps changing (gradually increasing) with time during the charging and discharging process. This is because the composition of the active material, the concentration of the electrolyte and the temperature are constantly changing. Ohm's internal resistance obeys Ohm's law, and the polarization internal resistance increases with the current density, but it is not a linear relationship. It usually increases with the current density.