Analysis of voltage knowledge about lithium batteries

The unit of measurement of lithium battery is working voltage (V), milliampere hour (mAh), and watt-hour (Wh), which is commonly used in laptop batteries. Usually when we compare battery capacity, we often use milliampere hour (mAh) as the unit of comparison. For example, when we were young, we played with four-wheel drive rechargeable batteries, mobile phone batteries, and mobile power batteries. Lithium batteries must be used with a suitable battery management system, otherwise it is very dangerous. The lithium battery with a lithium battery management system is generally called a lithium battery PACK. The nominal voltage of a single lithium battery is 3.7V, and the normal voltage range is 2.5V-4.25V. Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium batteries. Lithium batteries do not contain metallic lithium and are rechargeable. Its safety, specific capacity, self-discharge rate and cost performance are better than lithium batteries. Each category has different requirements for lithium batteries. For example, mobile phones require more battery life and volume, electric vehicles require more safety and battery life, and model airplanes and drones require more discharge rates. 1. Working voltage: refers to the potential difference between the positive and negative poles of the battery when the current flows through the circuit when the battery is in working state, also known as the load voltage. In the battery discharge state, when the current flows inside the battery, the resistance of the internal resistance has to be overcome, so the working voltage is always lower than the open circuit voltage. 2. Charging limit voltage: The charging voltage changes from constant current to constant voltage during charging. 3. Open circuit voltage: refers to the voltage when the battery is not connected to an external circuit or external load. The open circuit voltage has a certain relationship with the remaining energy of the battery, and the power display uses this principle. 4. Discharge cut-off voltage: refers to the voltage reached when the battery is discharged after being overcharged (if it continues to discharge, it is over-discharged, which will damage the battery's life and performance). The single working voltage of lithium battery is 3.7V or 3.2V. The voltage of a single-cell lithium battery is 3.7V (the lithium iron phosphate anode is 3.2V), and the capacity of the lithium battery cannot be infinite. Therefore, single-cell lithium batteries are often connected in series and parallel to meet the requirements of different occasions. . Generally speaking, the nominal voltage is the center voltage of the platform voltage. Near this voltage, the voltage changes slowly during charging and discharging. For example, the platform voltage of a nominal 3.7V lithium battery is around 3.7V, and the platform voltage of a nominal 3.2V lithium iron battery is around 3.2V. The charging voltages of lithium batteries and nickel-metal hydride batteries are different. The maximum charging voltage of a single lithium battery (3.6V) is 4.2V. Exceeding this voltage will cause the lithium battery to overheat or even explode. So use a special charger to charge the lithium battery. The 12V lithium battery pack can be charged with a 12V lithium battery charger. The voltage of the lithium battery is from 2.5V to 4.2V when it is working. When the voltage is less than 2.5V, the battery discharge is terminated. At the same time, because the discharge circuit is closed, the current loss of the internal protection circuit is also minimized. Of course, in actual applications, due to different internal Material, the discharge termination voltage can be in the range of 2.5V-3.0V. When the voltage exceeds 4.2V, the charging circuit is terminated to protect battery safety; and when the single lithium battery's operating voltage drops below 3.0V, we can consider it as over-discharged State, the discharge circuit is terminated to protect the battery safety. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: What are the misunderstandings about 18650 lithium batteries?