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
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