Starting from the high-precision test of power battery division and conversion, break through the cost and mileage anxiety of new energy vehicles

In the first half of 2019 , despite the sluggish trend of the overall automobile market, according to the latest data released by the Traffic Management Bureau of the Ministry of Public Security, the number of new energy vehicles in China reached 3.44 million, an increase of 72.85% compared with the same period last year, becoming the world's largest automobile industry. A rare hope for the auto market. As a key factor for the victory of new energy vehicles, the integration of battery channels and resources has become the focus of the world's major new energy vehicle manufacturing industry chain companies. Not long ago, Tesla CEO Elon Musk said that in order to obtain enough batteries, the company may enter the mining industry; Volkswagen decided to spend 1 billion euros to cooperate with European power battery startups to build its own battery factory; CATL and Toyota are in new energy vehicles. (NEV) The stable supply of power batteries and the establishment of a comprehensive partnership in the field of development and evolution...

There is no doubt that it is very important to master the security of the power battery supply chain and to achieve a stronger cost and performance competitive advantage from the power battery manufacturing side in today's increasingly fierce competition in the new energy vehicle market. "Consumers' new energy vehicle purchase decisions are mainly determined by three factors: safety, cost and mileage. This is also the goal of the joint efforts of OEMs and power battery manufacturers." Hu Shuoqiu, marketing manager of ADI's lithium battery test solution, in a recent interview He pointed out, "The cost and mileage are highly related to a key process in the manufacture of power batteries - volume separation and formation." Volume separation and formation is a key test link in the later stage of battery manufacturing, and it is a major provider of high-performance simulation technology. , ADI's insights on how to improve power battery performance and reduce costs from the manufacturing process may serve as an industry reference.

Alleviate the cost and mileage anxiety of lithium-ion battery manufacturing from key links

At present, new energy vehicle manufacturers are generally in the predicament of "anxiety" of batteries. Due to the development of fuel cell technology, it is difficult to apply and replace pure electric vehicles on a large scale in the short term, and new battery technology (lithium-air lithium-sulfur, etc.) is still in the In the basic research and development stage, lithium-ion batteries will be listed as the best choice in the field of new energy vehicle power batteries for a long period of time due to their light weight, high energy density, and environmental protection.

Typically, lithium-ion battery manufacturing procedures are complex, including electrode production, stack structure, and cell assembly, followed by electrical testing to assess battery capacity and performance, as well as in-service ratings. According to Hu Shuoqiu, capacity separation is the key to the manufacturing process of lithium-ion batteries. Both are through the precise control of the charging and discharging process of the battery. The former acts as an "activation", making the battery begin to have the ability to store and release electrical energy. The latter is to sort batteries with similar characteristics, improve the consistency of finished batteries, and ensure the high performance of vehicle power battery packs. It's a fairly time-consuming process that involves multiple charges and discharges to activate the battery's chemistry. But this process is necessary and critical to ensuring the reliability and quality of the finished battery.

Lithium-ion battery manufacturing process

According to Hu Shuoqiu, lithium-ion battery separation into capacity accounts for more than one-third of the total cost of the manufacturing process, so separation into capacity once became one of the bottlenecks that hindered battery manufacturers from increasing production and reducing the total cost of battery production. Lithium-ion battery manufacturers are eagerly looking forward to reducing the time required for separation and formation under the premise of ensuring safety in this field, collecting and monitoring the parameter changes of lithium batteries from more dimensions and with greater density, so that the charging and discharging process becomes More efficient power savings, reduced equipment footprint, and reduced cable usage and heat, ultimately reducing costs and improving energy efficiency. In addition, in order to improve the electrochemical performance of the battery such as cycle life, stability, self-discharge, and safety, the consistency of lithium batteries must be strictly controlled or the battery grade must be accurately assessed. Very demanding. Therefore, after taking into account factors such as cost, battery manufacturers are more inclined to work closely with suppliers with system-level expertise in formation testing, not only to obtain more complex components and building blocks, but also to obtain easier adoption The reference design of the latest system architecture makes the time-to-market three to four times faster than developing a formation and test system from scratch, while also ensuring the accuracy and reliability of battery formation and test measurements.

For battery test suppliers, it is not easy to meet the requirements of efficient and accurate battery separation and conversion testing. In the analog front end, the power supply driving the battery charging circuit needs to be tightly controlled. At a deeper level, battery formation and testing requires close monitoring of the current and voltage profiles used during battery cycling to prevent overcharging and undercharging. ADI is one of the few professional-level suppliers that can meet the needs of battery manufacturers for accurate battery formation testing.

ADI Innovation Delivers Measurable Results for Battery Formation and Test Equipment Manufacturers

A "Budge-Order" System-Level Solution for Battery Testing

Hu Shuoqiu mentioned that there are currently two schemes for formation and testing in the production process of lithium-ion electronics, one is a linear scheme, and the other is PWM (pulse width modulation). The power consumption of the linear scheme will be larger and require better cooling equipment. At present, the solutions on the market are also differentiated according to the size of the battery capacity. The small-capacity solution will still use a linear solution, which has low efficiency but low equipment cost. When it reaches 6A or more, the power consumption will increase, and it is more appropriate to use the PWM method. The AD8452 integrated chip for charging and discharging of ADI's battery formation and separation contains the crystallization of ADI's analog technology, which can improve the system accuracy and efficiency of the formation and separation of lithium-ion batteries. By integrating a high-precision front-end amplifier and a high-frequency PWM controller, the AD8452 can provide 50% more channels in the same space than conventional technologies, thereby expanding capacity and improving battery yield. Each AD8452 can control the charging and discharging current up to 30A individually, or can control multiple pieces in parallel to control a larger output current. In addition, the switching technology used in the AD8452 can recover the energy of the battery during discharge, and the accuracy is significantly higher than that of traditional switching solutions. The higher accuracy also means that more cells can be placed in the battery pack, helping to extend the electric vehicle. battery life of other applications.

At the same time, the AD8452 combines excellent detection and monitoring capabilities to effectively prevent overcharging and undercharging behaviors that can lead to battery failure, thereby increasing the safety of the manufacturing process. The device features a companion system emulation demonstration board that reduces R&D engineering costs and time-to-market for test equipment manufacturers, and allows manufacturers to design systems with more functionality and a more reliable test process.

In order to produce batteries faster at lower cost and obtain the capacity of lithium batteries more accurately, the battery system uses hundreds or thousands of channels in the formation and test phase, and its tester topology depends on the total energy capacity of the system. The error requirements of the current and voltage measurement of the charging and discharging of lithium batteries are also significantly increased. The accuracy of current and voltage control during charging and discharging largely determines the reliability of consistent control of lithium batteries, requiring high-performance instrumentation amplifiers and associated parallel resistors to measure battery charging and discharging currents, even under harsh factory conditions , but also to achieve an accuracy of more than ±0.05%, and the difference amplifier used to monitor the voltage over the entire thermal operating range also needs to be suitable for this accuracy level. "Many customers require the voltage test to achieve an error accuracy of 5/10,000 to 1/10,000, so the error requirements for the amplifier and ADC/DAC in the entire measurement control circuit are also increased accordingly." Hu Shuoqiu emphasized.

In fact, it is a huge challenge to combine the above functional components into a complete and accurate solution with the highest possible performance and reduced system footprint, and it is also a big challenge for ADI to integrate the analog front end, power control and monitoring circuits in a single IC One of the reasons in AD8452. Hu Shuoqiu pointed out: "ADI has a leading instrumentation amplifier technology. By integrating a high-performance instrumentation amplifier or differential amplifier with a gain setting resistor network into the chip, the AD8452 can reduce calibration time, reduce ripple, and current sharing through control loop design. Intelligent control functions such as control, provide a high level of current and voltage measurement accuracy, reduce calibration cycle time and frequency, and further increase uptime.” In addition, higher switching frequency brings design simplification and shrinking of electronic components, also Reduce the number of components required and charge and discharge circuit board layout, saving up to 50% bill of materials (BoM). All control operations can be done in the analog domain, without the need to develop complex algorithms, so this method can also effectively reduce software development costs. At the same time, ADI's current detection amplifier calibration and calibration technology simultaneously improves the level of lithium battery consistency control ability from multiple dimensions, and also contributes to the popularization of environmental protection technology.

Summary of this article

As Zhao Yimiao, general manager of ADI's System Solutions Division, pointed out at an industry summit in the first half of the year: "China's manufacturing industry is very fast in following up emerging industries, and there is little gap with the world's advanced level, such as the lithium battery industry. The booming development has driven the demand for lithium battery production and testing, and Chinese manufacturers are currently at the forefront of lithium battery testing." Battery technology is an important driving force for new energy vehicles. How to improve the measurement accuracy and service life of batteries and increase battery life Capability, cost reduction, and safe use are challenges faced by the entire industry. "In these fields, ADI is actively conducting research and has achieved a series of cutting-edge research results. For customers who have reached a strategic cooperation intention with ADI on AD8452, ADI is willing to discuss and cooperate on the future of lithium battery separation and formation. .