Lithium-ion batteries have become the preferred energy storage method due to their advantages such as high energy density, long service life, high power handling capacity, very low self-discharge rate, light weight, strong adaptability to high and low temperatures, and the fact that they do not contain or contain any toxic or harmful heavy metal elements and substances such as lead, mercury, and cadmium, regardless of production, use, or disposal.
As market expectations for lithium-ion batteries rise, superior manufacturing processes and technologies have become crucial for ensuring their performance advantages. Battery formation and capacity testing, essential steps in lithium-ion battery production, play a vital role in determining battery performance. The quality of formation directly impacts the initial efficiency, cycle life, thermal stability, and safety performance of the lithium-ion battery.
Generally, battery formation processes are divided into constant current charging, constant voltage charging, and constant power charging stages, as well as constant current discharging, constant power discharging, and constant resistance discharging stages. The battery formation process requires high precision in the measurement of charging and discharging current and voltage of lithium-ion batteries, with an ideal accuracy of 0.05% to 0.01% to ensure the overall accuracy of the formation equipment is within 0.1%. Therefore, suitable measurement methods are also crucial indicators for formation equipment. While commonly used shunt measurements can meet the accuracy requirements, their high common-mode voltage makes them unsuitable for use in formation equipment. General current sensors can achieve an accuracy of 0.2%, but this is insufficient to meet the high-precision requirements across the entire measurement range. Furthermore, the temperature requirements during the formation process necessitate low temperature drift.
As an expert in power measurement solutions, LEM has developed the high-precision IT/IN series current sensors, specifically designed for battery formation, based on its existing high-precision sensors. These sensors utilize closed-loop fluxgate technology and are compatible with both AC and DC sides of the formation equipment. Typically, the formation equipment uses three sensors on the AC side and two sensors on the DC side.
The table below compares the parameters of a typical Hall current sensor and a high-precision sensor. The IT/IN series sensors have significant advantages in measurement accuracy and temperature drift characteristics under low current conditions.
The IN series sensors employ patented innovative technology, utilizing a new fluxgate structure to eliminate ripple at the fluxgate drive frequency and reduce noise output. The excitation voltage conditioning circuit also features enhanced stability.
The new generation of IN sensors incorporates digital circuitry (DSp), which protects the sensor from the effects of temperature, interference, and power supply voltage variations, significantly improving zero-point error and temperature drift. It achieves an error of less than 10 ppm over a temperature range of -40 to +85°C and a linear error of 3 ppm across the entire measurement range.
The IN series retains the high-precision sensor features of its predecessors, equipped with LED indicators and providing high and low level auxiliary outputs. It can be interlocked with the control and protection system of the battery formation equipment to monitor in real time whether the sensor is in normal operating condition, thus improving the reliability and safety of the entire device.
