Lithium-ion battery pack assembly overview
1. The basic structure of the battery
The basic structure of the battery consists of three parts: the battery core, the protective plate and the outer shell.
1. Batteries: Batteries are the most important part of the battery and the carrier of energy conversion. Our company currently produces polymer lithium ion batteries and cylindrical lithium ion batteries. The basic parameters of the battery are: capacity, internal resistance, cycle life, etc.
2. Protection board: The protection board is an electronic functional module that protects the normal operation of the battery cell and prevents abnormal accidents. The main components are IC and MOS tube. The IC is a component that monitors the voltage of the cell, and the MOS tube is a switch. In the whole module, the IC controls the switching state of the MOS tube by detecting the current of the working circuit and the voltage across the battery core, thereby controlling the charging and discharging circuit, and achieving the purpose of preventing battery overcharge, overdischarge or overcurrent. The main parameters of the protection board are: overcharge protection voltage, overcharge protection recovery voltage, overdischarge protection voltage, overdischarge protection recovery voltage, short-circuit protection current, self-consumption current, PCM internal resistance, etc. The above parameters can be measured by special equipment or analog circuits.
3. Shell: The shell is a shell that fixes the battery core and the protection board together, seals and completes the matching function with the host. The outer shell is often divided into a bottom shell and a face shell. Generally, after mating with the host, the one that leaks outside is the face shell, and the other is the bottom shell.
Commonly used materials for the shell are: ABS, ABS+PC, PC, etc. The main indicators to measure the shell are: color, material, fit, mechanical strength, etc.
2. The key process of battery assembly
1. Tin soldering: Tin soldering is a process that uses solder wire to connect conductors together and achieve a good conduction effect. The factors that affect the quality of solder include soldering temperature, main body material, solder material and so on. In battery assembly, the welding temperature is generally required to be controlled at 360±10°C.
Materials that are easy to solder include gold, silver, copper, tin, nickel, steel, etc. The defects that are easy to appear in soldering are: false soldering, false soldering, over soldering, etc.
2. Plastic shell packaging (also known as ultrasonic welding and crimping): The packaging of commonly used plastic shells uses ultrasonic welding. The principle is to use ultrasonic waves to transfer energy to two contacting surfaces. High-frequency vibration of the contacting part generates heat and melts the contacting surface. And bonding.
The main parameters that affect ultrasonic welding are: equipment power, equipment energy, pressure, welding time, etc.
Three, test
1. Cell test: conventional items include: capacity, cycle life, internal resistance, voltage, self-discharge, etc. Other items include: high temperature discharge performance, low temperature discharge performance, short circuit, nail piercing, etc.
2. Protection board: electrical performance test parameters include: overcharge protection voltage, overcharge protection recovery voltage, overdischarge protection voltage, overdischarge protection recovery voltage, short circuit protection current, self-consumption, PCM internal resistance, etc. Shape and structure: The leaking part of the gold finger has no deviation, sinking, bright color and no spots, and the thickness of the gold layer is 0.3μm.
3. Finished battery: electrical performance testing items include: charge and discharge functions, short circuit protection function, open circuit voltage, over current, identification resistance, thermistor, battery internal resistance, etc. Appearance and structure inspection items include: kit effect, drop test, gap, color, etc.
