Battery capacity is one of the important performance indicators to measure battery performance. It represents the amount of power released by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.) (JS-150D can be used for discharge testing), that is, the battery capacity is usually in ampere hours (abbreviated as AH, 1Ah=3600C).

According to different conditions, battery capacity is divided into actual capacity, theoretical capacity and rated capacity. The calculation formula of battery capacity C is C=∫t0It1dt (integrated current I from t0 to t1), and the battery is divided into positive and negative electrodes.

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Nominal voltage is a technical term in physics, which refers to the voltage value corresponding to the nominal operating current of the thermistor adjusted at +25C. At present, the most commonly used regulated thermistor has a nominal voltage of 2 volts, and others include 3 volts, 4 volts, 5 volts and 6 volts. The nominal voltage is also a suitable voltage approximation to indicate or identify the battery, also known as the rated voltage, which can be used to identify the battery type.

The nominal voltage of a battery is an appropriate approximation of the voltage used to indicate or identify the battery, also known as the rated voltage, which can be used to identify the battery type. For example, the open circuit voltage of a lead-acid battery is close to 2.1V, and the nominal voltage is 2.0V. The nominal voltage of zinc-manganese dry batteries is 1.5V, the nominal voltage of nickel-cadmium batteries and nickel-hydrogen batteries is 1.2V, and the nominal voltage of lithium-ion batteries is 3.7V.

In fact, the nominal voltage does not represent the battery voltage. The actual voltage of the battery varies according to the actual capacity of the battery. In the market, in some cases, the nominal voltage of the same battery will be different in different scenarios or regions, but the battery is actually the same.

The internal resistance of the battery

The internal resistance of the battery refers to the battery resistance when current flows through the battery. It includes ohmic internal resistance and polarization internal resistance. Polarization internal resistance also includes electrochemical internal resistance and concentration polarization internal resistance.

Regarding lithium-ion batteries, the internal resistance of the battery is divided into ohmic internal resistance and polarization internal resistance. The ohmic internal resistance is composed of electrode material, electrolyte, diaphragm resistance and contact resistance of each part. Internal polarization resistance refers to the resistance caused by polarization during the electrochemical reaction, including resistance caused by electrochemical polarization and concentration polarization.

The actual internal resistance of a lithium-ion battery refers to the resistance experienced by the current flowing through the battery when the battery is working. The internal resistance of the battery is very large (during normal use), a large amount of Joule heat (according to the formula: E=I^2RT) will cause the battery temperature to rise and cause the battery to discharge and reduce the working voltage, shorten the discharge time, and seriously affect the performance of the battery And longevity.

The accurate calculation of the internal resistance of the battery is very complicated and will change continuously during the battery use. According to relevant relevant experience, the larger the volume of the lithium-ion battery, the lower the internal resistance; on the contrary, the lower the internal resistance of the lithium-ion battery. vice versa.

Self-discharge rate

Self-discharge rate, also known as charge retention capacity, refers to the retention capacity of the battery’s storage power under certain conditions when the battery is in an open circuit state. It is mainly affected by the battery manufacturing process, materials, storage conditions and other factors. This is an important parameter to measure battery performance.

The magnitude of self-discharge and the rate of self-discharge are related to the solubility of the cathode material in the electrolyte and its instability (easy to self-decompose) after heating. The self-discharge of rechargeable batteries is much higher than that of primary batteries. In addition, the monthly self-discharge rate of different types of batteries is also different. Generally, it varies between 10-35%. During storage, self-discharge is accompanied by an increase in the internal resistance of the battery, which will reduce the load capacity of the battery. In the case of a large discharge current, the energy loss changes significantly.