Li-Ion Battery Test Equipment Solutions Application Introduction Lithium-ion (Li-ion) batteries offer many benefits over other battery chemistries. For example, when compared with nickel-metal hydride batteries or nickelcadmium batteries, they are lighter, do not suffer from memory effect, and have a lower self-discharge rate. Li-ion batteries have been widely used as rechargeable batteries in modern electronic devices, like smartphones and laptop computers. Due to the clean energy requirements, Li-ion batteries have recently also become popular in high power applications like electronic vehicles, electronic tools, and energy storage. With the fast growth of the Li-ion battery, the test equipment used during its manufacturing process has become critical, too. The typical functions of Li-ion battery test equipment are shown below. • Formation and grading: Once the battery cell assembly is complete, each cell must be put through at least one precisely controlled charge/discharge cycle to activate the working materials, transforming them into their useable form. The battery vendors can also use this process to sort their cells into different performance groups to sell them according to alternative specifications, which is called grading. • Cycling and characterization: Cycling charges and discharges the battery cells and battery packs many times to perform lifetime and reliability tests. Characterization is to measure and record the battery’s specifications in great detail. Generally, both tests take a very long time, more than one day, and only some sample batteries are selected to perform such tests in the lab. • Functional test: To ensure each battery cell and battery pack works properly before shipping to end customers each battery will be functionally tested after manufacturing. To shorten test time, the functional test includes only necessary items. System Design Considerations and Major Challenges To increase the throughput of Li-ion batteries in the manufacturing process, the test time is an important factor. However, the normal formation time of a Li-ion battery cell is a minimum of two to five hours, which cannot be reduced due to the nature of the materials inside the cell. Thus, the channel count of a Li-ion battery tester is high, up to 1024 channels or more, to test many batteries in parallel and increase the throughput. Because high capacity Li-ion batteries also need high charging currents, the power consumption of a Li-ion battery test system can be large, which means that the first challenge of a Li-ion battery tester is to improve its energy utilization efficiency. For that reason, the recent trend is to replace traditional linear testers with efficient switching testers. In addition, the energy recycle technique has been implemented in advanced battery test equipment. The second challenge of the Li-ion battery testers is to have more accurate control in the charging and discharging loops. To reduce the charging time, most users select the constant current (CC) charging mode first and then switch to the constant voltage (CV) charging mode. The transition between CC and CV modes needs to be well controlled to avoid overshoot (overcharging). In addition, the heat generated by the energy loss will cause drift and affect system accuracy and safety. The third challenge of the Li-ion battery testers is to reduce the test cost to compete with other kinds of batteries. Besides the cost of the tester itself, the test time and energy consumption are also major sources of the test cost. Li-ion battery tester designers need to use some advanced topologies and techniques to lower the cost without compromising the accuracy. Exceeding a battery’s temperature rating during charge or discharge can reduce its cycle life. In the worst case, excessive temperatures may cause batteries to rupture or even cause fires. For this reason, it is important to monitor and control the cell temperature of Li-ion batteries during charge and discharge cycles. Solutions from ADI ADI solution value proposition: • One stop shopping to provide the broadest product portfolios in the Li-ion battery test equipment signal chain, like amplifiers, ADCs, DACs, isolators, and processors. • ADI’s product compatibility supports design migration across multiple platforms, such as pin compatible level setting DACs for different resolutions. • On-chip integration optimizes signal chain performance and minimizes board space and BOM cost, such as the instrumentation and difference amplifiers that integrate high performance operational amplifiers and resistors to achieve an outstanding common mode rejection ratio(CMRR) and drift. • Extensive design resources, like easy-to-use simulation tools (ADIsimPower ,™ DiffAmpCalc™), forums in ADI’s EngineerZone™ website, and fully-populated evaluation boards. • Circuits from the Lab™ reference circuits are engineered and tested for quick and easy system integration to help solve today's analog and mixed-signal design challenges. Web-based design tools optimize performance of custom designs. Some Web-based examples are shown in the end of this document. instrumentation.analog.com System Block Diagram A high-level overview of a Li-ion battery test system is shown below. A7. DIGITAL ISOLATION POWER CHAIN A1. AC-TO-DC POWER FACTOR CORRECTION CONTROL (PFC) 1-PHASE/ 3-PHASE AC POWER C. POWER GENERATION AND MANAGEMENT A2. ISOLATED DC-TO-DC CONTROL A8. FAST PROTECTION (OVP, OCP, OTP) ETHERNET Tx/Rx B. A3. ISOLATED RS-485 Tx/Rx POWER GRID ETHERNET Tx/Rx A6. PROCESSOR A3. ISOLATED RS-485 Tx/Rx A4. ISOLATED CAN Tx/Rx A4. ISOLATED CAN Tx/Rx B. A1. Power Factor Correction Control ADP1047 ADP1048 B. A3. ISOLATED RS-485 Tx/Rx UART/USB FOR HUMAN MACHINE INTERFACE (HMI) − DEVICE UNDER TEST (DUT 3) BAY X ETHERNET Tx/Rx INTERNET TO REMOTE SERVERS AND USERS + LINEAR/SWITCHING CHARGE/DISCHARGE CONTROL UNIT 1024 OR MORE CHANNELS A5. ISOLATED RS-232/USB − DEVICE UNDER TEST (DUT 2) BAY 2 ETHERNET Tx/Rx A3. ISOLATED RS-485 Tx/Rx + LINEAR/SWITCHING CHARGE/DISCHARGE CONTROL UNIT A4. ISOLATED CAN Tx/Rx CENTRAL CONTROL UNIT DEVICE UNDER TEST (DUT 1) BAY 1 + LINEAR/SWITCHING CHARGE/DISCHARGE CONTROL UNIT A4. ISOLATED CAN Tx/Rx − A2. Isolated DC-to-DC Control A3. Isolated RS-485 Tx/Rx A4. Isolated CAN Tx/Rx A5. Isolated RS-232/USB A6. Processor A7. Digital Isolation A8. Fast Protection ADP1043A ADM2582E ADM2682E ADM3052 ADM3053 ADM3251E ADuM3160 ADSP-BF548 ADSP-BF516F ADuM7441 ADuM1201 AD8214 ADT6402 A more detailed diagram of the linear/switching charge/discharge control unit is shown below. SYSTEM BUS RS-485/CAN LINEAR/SWITCHING POWER TRANSISTOR STAGE B1. POSITIVE CLAMP SET DAC CHARGE/ DISCHARGE B1. CURRENT SET DAC A6. PROCESSOR B2. CURRENT SENSE AMP B1. VOLTAGE SET DAC B1. NEGATIVE CLAMP SET DAC CURRENT VOLTAGE B7. ADC B6. ADC DRIVER B8. REFERENCE VOLTAGE B3. VOLTAGE SENSE AMP TEMPERATURE B5. ANALOG MULTIPLEXER B4. THERMAL -COUPLE AMP WITH CJC + − B1. Level Setting DAC B2. Current Sense Amplifier B3. Voltage Sense Amplifier B4. Thermocouple Amplifier B5. Analog Multiplexer B6. ADC Driver B7. ADC B8. Reference Voltage AD8226, AD8228 AD8217 AD8638, AD8677 AD8276, AD8277 AD8638, AD8677 AD8494, AD8495 AD8496, AD8497 ADG5404 ADG5409 ADG5204 ADA4940 AD7606, AD7609 AD7691, AD7693 AD7490 ADR3425 ADR3433 ADR3450 AD5668, AD5628 AD5664, AD5064 A more detailed diagram of power generation and management is shown below. C1. SWITCHING CONTROLLER 1-PHASE/ 3-PHASE AC POWER A1. AC-TO-DC POWER FACTOR CONTROL (PFC) A2. ISOLATED DC-TO-DC CONTROL EXTERNAL MOSFETS C2. SWITCHING REGULATOR C5. POWER SEQUENCING V1 V2 C6. POWER SUPERVISORY POWER GRID C3. LOW NOISE LINEAR REGULATOR V3 V4 C4. PMU C1. Switching Controller ADP1870 ADP1874/ADP1875 ADP1878/ADP1879 C2. Switching Regulator C3. Low Noise Linear Regulator C4. Integrated Power Management Unit (PMU) C5. Power Sequencing C6. Power Supervisory ADP2323 ADP2300 ADP2301 ADP150 ADP320, ADP322 ADP323 ADP7102/ADP7104 ADP5034 ADP5040, ADP5041 ADP5042, ADP5043 ADM1085 ADM1086 ADM1087 ADM1191, ADM1192 ADM13305, ADM13307 Notes: The signal chains above are representative of Li-ion battery test equipment design. The technical requirements of the blocks vary, but the products listed in the table below are representative of ADI's solutions that meet some of those requirements. Main Products Part Number Description Key Specs and Features Benefits ADP1047/ ADP1048 Digital power factor correction controller Frequency range: 30 kHz to 400 kHz, single ADP1047 and interleaved ADP1048 phase outputs, PMBus/I2C interface True rms ac power metering, inrush current control, flexible ADP1043A Digital controller for isolated power supply applications Digital loop control, I2C interface, 7 programmable PWM outputs, remote and local voltage sense Current sharing, integrated programmable loop filter, intensive fault detection and protection ADM2682E 5 kV rms signal and power isolated RS-485 transceiver Connect up to 256 nodes on the bus, half and full duplex, 16 Mbps data rate, open/short fail safe Integrated isolated dc-to-dc converter, ±15 kV ESD protection on RS-485 in pins/out pins ADM3053 2.5 kV rms signal and power isolated CAN transceiver Connect 110 or more nodes on the bus, 1 Mbps data rate, high common mode transient immunity (> 25 kV/µs) Integrated isolated dc-to-dc converter, slope control for reduced EMI, thermal shutdown ADSP-BF548 533 MHz (1066 MMACs) Blackfin® processor 2 independent DMA controller, high speed USB OTG, CAN Lockbox® secure technology, human interface (LCD/keypad...) ADSP-BF516 400 MHz (800 MMACs) Blackfin Ethernet, SDIO processor Lockbox secure technology, human interface (LCD/keypad...) AD5668 Octal level setting DAC On-chip 5 ppm/°C reference, low power, small size, LDAC and CLR 12-bit/14-bit/16-bit pin-compatible family(AD5628/AD5648/AD5668) AD8228 Low gain drift precision instrumentation amplifier Pin strappable gains of 10/100, wide supply range ±2.3 V to ±18 V 2 ppm/°C gain drift, 0.8 µV/°C input offset drift (b grade G = 10) AD8276 Low power difference amplifier Unity gain, wide supply range ±2 V to ±18 V 1 ppm/°C gain drift, 2 µV/°C input offset drift, dual version available (AD8277) Main Products (continued) Part Number Description Key Specs and Features Benefits AD8494 Thermocouple amplifier with cold junction compensation Pre trimmed for J type or K type, standalone 5 mV/°C thermometer, internal cold junction compensation Pre-trimmed for J type or K type. Other optimized temperature ranges are available (AD8495/AD8496/AD8497) ADG5404 Latch-up proof multiplexer 4-channel multiplexer, ±9 V to ±22 V dual supply operation, 9 V to 40 V single supply operation, 8 kV ESD performance Guaranteed latch-up proof low on-resistance (<10 Ω) ADA4940 Ultralow power, low distortion ADC driver Supply voltage: 3 V to 7 V, rail-to-rail output, 16 bit settling time: 85 ns, Low quiescent current of 1.25 mA able to drive low harmonic distortion: −90 dB THD @ 2 MHz, low input voltage noise: 4 nV/√Hz 16-bit to 18-bit SAR ADC dual version available AD7609 DAS with 18-bit, simultaneous sampling 8 simultaneous sampling inputs, bipolar input ranges, +/10 V, ±5 V Single 5 V analog supply, fully integrated data acquisition solution ADT7310 SPI digital temperature sensor ±0.5˚C accuracy from −40°C to 105°C, 16-bit resolution No calibration required, I2C version available (ADT7410) ADP2323 20 V dual 3 A synchronous step-down regulator PWM/PFM mode selectable, flexible current limit set Sync input/output and phase shift function for low noise design, achieve high efficiency with low side MOSFET ADP5041 Power management unit (PMU) One 1.2 A buck, two 300 mA LDOs, supervisory, watchdog, manual reset ADP7102/ ADP7104 20 V, ultralow noise, 300 mA and 500 mA LDO Integration makes design smaller and BOM cost lower Low noise performance 15 µV rms for fixed voltage output, high PSRR 60 dB at Improves performance of noise sensitive loads 10 kHz, reverse current protection, wide range voltage input 3.3 V to 20 V Design Resources Circuits from the Lab™ Reference Circuits for Li-ion Battery Test Equipment • Lithium Ion Battery Stack With Both Signal and Power Isolation (CN0197)—www.analog.com/CN0197 • Low Cost Programmable Gain Instrumentation Amplifier Circuit Using The ADG1611 Quad SPST Switch and AD620 Instrumentation Amplifier (CN0146)—www. analog.com/CN0146 • 500 V Common-Mode Voltage Current Monitor (CN0218)—www.analog.com/CN0218 • Robust, Multivoltage, High Efficiency, 25 W Universal Power Supply Module with 6V to 14V Input (CN0190)—www.analog.com/CN0190 • Precision, Low Power, Single-Supply, Fully Integrated Differential ADC Driver for Industrial Level Signals (CN0180)—www.analog.com/CN0180 Technical Articles/Application Notes • Difference Amplifier vs. Current Sense Amplifier. Analog Dialogue Volume 42-01, January 2008 (High Side Current Sensing)— wwww.analog.com/analogDialogue/diffamp_currentamp • Isolation in High-Voltage Battery Monitoring for Transportation Applications. Analog Dialogue Volume 43, October 2009— www.analog.com/analogDialogue/HVBM • Designing an Inverting Buck Boost Using the ADP2300 and ADP2301 Switching Regulators (AN-1083)—www.analog.com/AN-1083 • Thermocouple Linearization When Using the AD8494/AD8495/AD8496/AD8497 (AN-1087)—www.analog.com/AN-1087 • Selecting The Right Passive and Discrete Components for Top System Performance (MS-2208)—www.analog.com/MS-2208 • Switch and Multiplexer Design Considerations for Hostile Environments—www.analog.com/library/analogDialogue/archives/45-05/switch_mux • ADP1043A Evaluation Board Quarter Brick Full Bridge—www.analog.com/PRD1153_ADP1043a_qb300w Design Tools/Forums • ADI’s Fastest and Most Accurate DC-to-DC Power Management Design Tool (ADIsimPower™)—www.analog.com/ADIsimPower • ADI’s Differential Amplifier Calculator (DiffAmpCalc™)—www.analog.com/diffampcalc • Online Technical Support Community (EngineerZone™)—ez.analog.com • Free, Downloadable Version of National Instruments Multisim 11 Circuit Simulation Software, Tailored for Evaluating ADI Components (NI Multisim™ Component Evaluator Analog Devices™ Edition)—www.analog.com/multisim To view additional signal generator resources, tools, and product information, please visit instrumentation.analog.com ©2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. BR103383-0-11/11 Customer Interaction Center cic.asia@analog.com EngineerZone ez.analog.com Free Sample www.analog.com/sample instrumentation.analog.com