Battery Capacity
Battery capacity is one of the important performance indicators to measure the performance of a battery. It indicates 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), i.e. battery capacity is usually measured in ampere-hours (abbreviated as AH, 1Ah = 3600C).
Depending on the conditions, battery capacity is divided into actual capacity, theoretical capacity and rated capacity. Battery capacity C is calculated by the formula C = ∫t0It1dt (integral current I from t0 to t1), and the battery is divided into positive and negative terminals.
Nominal Voltage
Nominal voltage is a technical term in physics that refers to the voltage value corresponding to the nominal operating current of a regulated thermistor at + 25°C. Currently, the most commonly used regulated thermistors have a nominal voltage of 2 volts, others include 3 volts, 4 volts, 5 volts and 6 volts. The nominal voltage is also an approximation of the appropriate voltage 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 and is also referred to as the rated voltage and can be used to identify the battery type. For example, lead-acid batteries have an open circuit voltage close to 2.1V and a nominal voltage of 2.0V. Zinc-manganese dry cell batteries have a nominal voltage of 1.5V, nickel-cadmium and nickel-metal hydride batteries have a nominal voltage of 1.2V, and lithium-ion batteries have a nominal voltage of 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 some cases in the market, the nominal voltage of the same battery can vary in different scenarios or regions, while the battery is actually constant.
Internal resistance of the battery
The internal resistance of a battery is the resistance of the battery as current flows through it. It includes ohmic internal resistance and polarized internal resistance. The polarization internal resistance also includes the electrochemical pole internal resistance and the concentration difference polarization internal resistance.
For lithium-ion batteries, the internal resistance of the battery is divided into ohmic internal resistance and polarized internal resistance. Ohmic internal resistance consists of electrode material, electrolyte, diaphragm resistance and contact resistance of each part. Internal polarization resistance is the resistance caused by the polarization during the electrochemical reaction, including the resistance caused by the electrochemical polarization and the concentration difference polarization.
The actual internal resistance of a lithium-ion battery is the resistance experienced by the current flowing through the battery when it is operating. A large internal resistance of the battery (during normal use) and a large amount of Joule heat (according to the equation: E = I ^ 2RT) will cause the battery temperature to rise and lead to discharge of the battery to reduce the operating voltage and shorten the discharge time, seriously affecting the performance and life of the battery.
The accurate calculation of the internal resistance of the battery is very complicated and will change continuously during the battery's use. According to relevant experience, the larger the volume of lithium-ion battery, the smaller the internal resistance; conversely, the smaller the internal resistance of lithium-ion battery. And vice versa.
Self-discharge rate
Self-discharge rate, also known as charge retention capacity, refers to the retention capacity of the battery's stored power under certain conditions when the battery is in the open circuit state. It is mainly affected by the battery manufacturing process, materials, storage conditions and other factors. It is an important parameter to measure the performance of the battery.
The size of self-discharge, self-discharge rate is related to the solubility of the cathode material in the electrolyte and its instability (easy self-decomposition) after heating. The self-discharge of rechargeable batteries is much higher than that of primary batteries. In addition, the monthly self-discharge rate of batteries varies for different types of batteries. It generally 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 high discharge current, the energy loss changes significantly.
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