According to statistics from the China Association of Automobile Manufacturers, in 2017, the production and sales of new energy vehicles in China were both close to 800,000, reaching 794,000 and 777,000 respectively. Among the new energy passenger vehicles, the production and sales of pure electric passenger vehicles (EVs) 478,000 vehicles and 468,000 vehicles were completed, representing a year-on-year increase of 81.7% and 82.1%, respectively.
The growing demand for electric vehicles has naturally increased the demand for batteries, but the production of batteries is time-consuming, creating a supply bottleneck, and its cost is high, accounting for up to 40% of EV costs. At present, whether small-volume, small-capacity or large-volume, large-capacity batteries are widely used in electric vehicles, they need to go through two processes before leaving the factory: formation and capacity separation. The formation process is the process of the battery from ineffective to effective, in short, the battery is activated. After it is formed, the capacity is divided, that is, the capacity size is determined. These two steps determine the performance indicators of lithium-ion batteries, and the consistency of lithium-ion batteries directly affects the cruising range of electric vehicles.
Therefore, in the battery completion stage, especially the battery formation and testing, it is particularly challenging, and its cost accounts for as high as 20%~30% of the battery cost. For battery makers and instrumentation providers, scaling EV production and improving efficiency are key to capturing this opportunity in the electric vehicle market. How to reduce the time and cost of battery formation and testing? In a recent speech, the industry’s semiconductor solution provider ADI’s automotive technology experts mentioned two secrets of ADI’s breakthrough in battery production efficiency.
ADI Innovation Delivers Measurable Results for Battery Formation and Test Equipment Manufacturers
Tip 1: Enable flexible multi-channel, both capacity and accuracy increase
At present, there are two kinds of schemes for dividing into capacity, one is a linear scheme, and the other is PWM (Pulse Width Modulation, 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 the linear solution, which has low efficiency but low equipment cost. When the power consumption is above 6A, the power consumption will be much higher. Suitable.
ADI’s current integrated precision solution for battery test and formation, the AD8452, integrates an analog front end, controller and PWM to improve system accuracy and efficiency for lithium-ion battery formation and grading. Compared with traditional technology, the new AD8452 can provide 50% more channels in the same space, thereby expanding capacity and improving battery yield. At the same time, the switching technology used in the AD8452 can recover the energy of the battery during discharge with up to 10 times the accuracy of traditional switching solutions. Higher accuracy means more cells can fit in a battery pack, which helps extend battery life in applications such as electric vehicles.
In addition, the AD8452 combines better detection and monitoring capabilities to prevent overcharge and undercharge behaviors that can lead to battery failure, improving the safety of the manufacturing process. The AD8452 can save up to 50% in bill of materials (BoM) costs for charge/discharge boards and around 20% in system costs. The device features a companion system emulation demonstration board that reduces R&D engineering costs and time-to-market for test equipment manufacturers.
Tip 2: Accurate analog controller, high-efficiency lithium-ion battery manufacturing
ADI also has deep insights into how to produce batteries faster and at lower cost. At present, high-quality, high-power lithium-ion battery cells represent the best solution available today and are widely used in notebook computers, mobile phones, digital cameras, video cameras and other portable devices, but production efficiency has not become a major issue because These batteries have a lower capacity, typically less than 5 amp-hours (Ah) per cell or group. A typical battery pack consists of less than a dozen cells, so matching isn’t a big deal.
However, batteries used in vehicles or electrical energy storage have much higher capacities, typically several hundred Ah. This is achieved with a large number of small battery cells or some high capacity batteries. For example, a certain model of electric vehicle uses about 6800 18650 lithium-ion battery cells and weighs 450 kg. For this reason, battery production requires faster manufacturing, higher efficiency and more precise control to meet market price demands.
A typical lithium-ion battery manufacturing process is shown in the figure below. The battery formation and testing in the off-line conditioning step not only has a great impact on battery life and quality, but also is a bottleneck in the battery production process. With current technology, formation must be done at the cell level, which can take hours or even days, depending on the battery chemistry. A current of 0.1 C (C is the battery capacity) is usually used during formation, so a full charge-discharge cycle will take 20 hours, and a typical test sequence includes multiple charge-discharge cycles.
Lithium-ion battery manufacturing process
To produce batteries faster and at a lower cost, the system uses hundreds or thousands of channels during the formation and test phases, and its tester topology depends on the total energy capacity of the system. Formation and electrical testing have strict accuracy specifications, with current and voltage controlled to within ±0.05%. High currents in testers can cause large temperature rises, making it difficult to maintain high measurement accuracy and repeatability over time. Analog Devices’ family of precision integrated analog front ends, controllers, and PWM products for battery test and formation systems simplifies system design through control loop design, reduced calibration time, reduced ripple, and current sharing control. The system accuracy of 0.05% and the energy efficiency of over 90% help to solve the bottleneck problem of rechargeable battery manufacturing, and at the same time contribute to the popularization of environmental protection technology.
Typical Li-ion battery charge-discharge curve
Establish industry standards to create better and faster battery formation and testing solutions
There has been an industry effort to develop standards for battery formation and testing, which are key to ensuring battery quality and safety. Continued research by the world’s leading semiconductor solution providers such as ADI has resulted in new products, reference designs and integrated solutions that not only achieve high accuracy, but also allow manufacturers to produce cells more efficiently and increase factory output. All of this can help scale up battery formation and testing, so customers can better scale their EV production.
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