Common terms of automobile battery

discharge
The process by which a battery delivers current to an external circuit. The discharge method can be divided into constant current discharge and constant resistance discharge, as well as continuous discharge and intermittent discharge. Continuous discharge is a discharge method that continuously discharges to the termination voltage under specified discharge conditions. Intermittent discharge refers to the discharge method of the battery under the specified discharge conditions, which is carried out intermittently until the specified termination voltage. Discharge capacity: the discharge capacity or effective working time of the battery under the standard conditions. Storage life: When the battery is stored under the specified conditions, it can still maintain the specified performance. Battery terminal: the part of the battery connected to the external circuit. Electromotive force: the difference between the equilibrium potentials of the two electrodes that make up the battery. It reflects the possibility of the external electric work of the battery.
short circuit
The positive and negative poles of the battery are directly connected. Short-circuit current: the current flowing immediately after the battery is short-circuited. Discharge rate: discharge rate refers to the rate of discharge, which is often expressed by "time rate" and "multiple rate". Hour rate refers to the discharge rate expressed in discharge time (h), that is, the number of hours required to discharge the rated capacity at a certain discharge current. For example, if the rated capacity of the battery is 30 Ah and the battery is discharged at 2A current, the hour rate is 30 Ah/2 A=15 h, which means that the battery is discharged at 15 hour rate. Multiply refers to the current output when the battery releases its rated capacity within the specified time, which is equal to the multiple of the rated capacity. For example, a discharge rate of 2 times indicates that the discharge current value is 2 times the battery capacity. If the battery capacity is 3 Ah, then the discharge current should be 2x3 two 6 Ao, which is visible. If the 2-rate discharge is converted into an hour rate, then it is 3 Ah/6 A=1/2 hour rate. The time rate and magnification are reciprocal to each other. DOD (depth of discharge): the percentage of the ratio of discharge capacity to rated capacity. Active substance: electrode material that can produce electric energy through oxidation or reduction reaction during battery discharge.
charge
The operation process of converting the electrical energy from the external circuit to the battery into chemical energy and storing it. Charging rate: the current value required to charge the battery to the rated capacity within the specified time, or the time required to charge the battery to the rated capacity under a certain current. Similar to the discharge rate, it is generally expressed by multiple (several C) or time rate. Constant voltage charging: a charging method that keeps the voltage at the charger end unchanged during charging. Constant current charging: a charging method in which the charging current remains unchanged during charging. Polarization: Polarization refers to the change of battery voltage and electrode potential caused by the battery from static state (current i20) to working state (i>o). The product of voltage and current is equal to power, and then multiplied by the battery operation time to output electric energy, so the polarization phenomenon reflects the energy loss from the static state to the working state, so the smaller the polarization loss is, the better. Common polarization phenomena include anodic polarization, cathodic polarization, ohmic polarization (resistance polarization), concentration polarization and electrochemical polarization. Polarization can also be understood as deviation from equilibrium. The thermodynamic equilibrium process is closely related to the reversible phenomenon. The rate of change of reversible process or equilibrium process is very small, but the actual process must have a certain rate, and sometimes requires a high rate. For example, modern electric steam
Polarization phenomenon
One of the requirements of the car is to have large current discharge. That is, the reaction rate is required to be large, which will inevitably lead to the phenomenon of deviation from the equilibrium value, that is, polarization. The resistance of the battery includes the resistance of the electrolyte, the resistance of the electrode material, and even the resistance caused by the attachment of the reaction products (such as hydroxide precipitation on the electrode). Ohmic polarization refers to the polarization caused by this. Concentration polarization is the deviation of the electrode potential from the equilibrium value caused by the change of the concentration of the agent during the electrochemical reaction. The positive and negative polarization refers to the phenomenon that the positive and negative potentials deviate from the static state values after the battery enters the working state. Any electrode process includes the process of one or more reaction particles receiving or losing electrons. The polarization caused by this process is called electrochemical polarization.
Charge rate (C-rate): C is the first letter of Capacity, which is used to indicate the current value of the battery during charging and discharging. For example, when the rated capacity of the rechargeable battery is 1100mAh, it means that the discharge time at 1100mAh (1C) can last for 1 hour. If the discharge time at 200mA (0.2C) can last for 5 hours, the charging can also be calculated according to this comparison.
Cut-off discharge voltage: refers to the lowest working voltage that the battery should not continue to discharge when the battery is discharged. According to different battery types and different discharge conditions, the requirements for battery capacity and life are also different, so the specified battery discharge termination voltage is also different.
Open circuit voltage (OCV): When the battery is not discharged, the potential difference between the two poles of the battery is called open circuit voltage. The open-circuit voltage of the battery will vary according to the materials of the positive and negative electrodes of the battery and the electrolyte. If the materials of the positive and negative electrodes of the battery are the same, the open-circuit voltage will be the same regardless of the size of the battery and the change of its geometry.
Depth of discharge DOD: the percentage of the discharged capacity of the battery in its rated capacity during the use of the battery, which is called the discharge depth. The depth of discharge is closely related to the charging life of the secondary battery. When the depth of discharge of the secondary battery is deeper, its charging life is shorter. Therefore, deep discharge should be avoided as far as possible during use.
Over-discharge: If the battery exceeds the end voltage of the battery discharge during the discharge process and continues to discharge, the internal pressure of the battery may increase, the reversibility of the positive and negative active substances may be damaged, and the capacity of the battery will be significantly reduced.
Overcharge: When the battery is charged, if it continues to be charged after reaching the full state, it may lead to the increase of the internal pressure of the battery, the deformation of the battery, the leakage of liquid, and the performance of the battery will also be significantly reduced and damaged.
Energy density: the electric energy released by the average unit volume or mass of the battery. Generally, in the same volume, the energy density of lithium ion batteries is 2.5 times that of nickel cadmium batteries and 1.8 times that of nickel hydrogen batteries. Therefore, in the case of equal battery capacity, lithium ion batteries will be smaller and lighter than nickel cadmium and nickel hydrogen batteries.
Self discharge: The phenomenon that the battery will lose its power due to various reasons whether it is in use or not. If the unit is one month, the self-discharge of lithium ion battery is about 1% - 2%, and that of nickel hydrogen battery is about 3% - 5%.
Cycle life: the capacity of rechargeable battery will gradually drop to 60% - 80% of the initial capacity under repeated charging and discharging.
Memory effect: In the process of battery charging and discharging, many small bubbles will be generated on the battery plate. Over time, these bubbles will reduce the area of the battery plate and indirectly affect the battery capacity.