Battery Types
There are many different battery types, each with their own advantages and disadvantages. Different industries base their selections on the specific requirements of the application. Generally, manufacturers will consider cost, energy density, cycle life, and environmental impact when selecting the appropriate battery type for a given application.
Different battery types include:
Lithium-ion (Li-ion)
Li-ion batteries use lithium-ion chemistry, which is known for its high energy density making them lightweight and compact. They have gained popularity in automotive, consumer devices and portable medical instruments due to their high energy density, longer cycle life, lower self-discharge rate and relatively lightweight design. They are used for both propulsion and auxiliary power in modern vehicles. With their long cycle life, they are ideal for devices that experience frequent charge and discharge cycles and are extremely reliable. On the flip side, Li-ion batteries can be more expensive to manufacture and can be damaged if overcharged, potentially leading to safety issues. Disposal and recycling of Li-ion batteries require careful management due to their chemistry.
Lead-Acid Batteries
Lead-acid batteries use a lead dioxide positive electrode, a sponge lead negative electrode, and a sulfuric acid electrolyte. They are relatively inexpensive to produce, making them popular for automotive and industrial applications. They are also used in larger medical equipment, such as uninterruptible power supplies (UPS) for hospitals or backup power systems, but they are heavy and have low energy density, making them less suitable for portable applications. They can handle deep discharges and provide a reliable source of power but there is a limited number of charge and discharge cycles before their performance degrades.
These are the traditional and most widely used batteries in internal combustion engine (ICE) vehicles. They are affordable and provide the necessary cranking power to start the engine. Absorbent Glass Mat (AGM) Batteries are a variation of lead-acid batteries that offer improved performance, especially in start-stop systems and vehicles with higher electrical loads.
Nickel-Cadmium (NiCd) Batteries
NiCd batteries use a nickel oxide-hydroxide positive electrode, a cadmium negative electrode, and a potassium hydroxide electrolyte. Cadmium is toxic, so NiCd batteries pose environmental concerns and require proper recycling. They are known for their durability and resistance to extreme temperatures. They can provide high current output, making them suitable for power tools and other high-demand applications and can endure many charge and discharge cycles. NiCd batteries are known to experience the memory effect, which reduces capacity if not discharged fully before recharging and have lower energy density.
Nickel-Metal Hydride (NiMH) Batteries:
NiMH batteries are used in medical devices where cost-effectiveness and environmental considerations are important. These batteries are less toxic than NiCd batteries, which makes them more environmentally friendly. They have a relatively high energy density, are cost-effective and have a relatively low self-discharge rate making them suitable for certain portable medical equipment and devices that aren’t constantly in use. NiMH batteries have been used in hybrid vehicles for many years.
Alkaline Batteries:
Alkaline batteries have a long shelf life, making them suitable for devices that may be stored for extended periods. They can often be found in many forgotten drawers in homes since they are commonly used for remote controls, flashlights, toys, etc. That said, they are also often used in single-use or disposable medical devices, like hearing aids since they are cost-effective and readily available.
Zinc-Carbon Batteries:
Zinc-carbon batteries are the least expensive option and are used in very basic consumer electronics like low-cost toys, clocks, and small gadgets. They have a shorter lifespan and are typically non-rechargeable.
Lithium Polymer (LiPo) Batteries:
LiPo batteries are a variation of Li-ion batteries and are known for their flexibility in terms of shape and size. They are used in slim and lightweight devices, such as drones, remote-controlled toys, and some smaller laptops. LiPo batteries are often chosen when manufacturers need custom-shaped batteries to fit within specific device designs.
Custom Battery Packs:
Alternately it is not uncommon for medical device manufacturers or electronics manufacturers to customize batteries to meet specific voltage, capacity, and size requirements. Custom packs can include various battery chemistries, such as Li-ion, Li-polymer, or NiMH, tailored to the device's needs.
Solid-State Batteries:
While still in development and not as commonly used as the previous types, solid-state batteries are gaining attention in the automotive industry due to their potential for higher energy density, longer life, and improved safety. They are being researched and developed for use in electric vehicles.
Battery Components
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All batteries are made up of 4 key elements:
1. Battery Cells:
The basic building blocks of battery systems, typically cylindrical, pouch or prismatic, containing the electrochemical core.
Pouch cells can offer a higher energy density than other form factors, but they may be less durable due to the absence of a protective metal casing.
Battery cell form factors refer to the physical shape and size of batteries.
Different form factors are designed for various applications and have distinct characteristics.
Here are some of the more common battery cell form factors and their differences:
- Cylindrical Cells - Cylindrical cells are the most common and widely used battery form factor. They are available in various sizes, with the most common being AA, AAA, and 18650. Cylindrical cells have good energy density and can handle high discharge rates. They are often used in consumer electronics, flashlights, and some portable devices.
- Prismatic Cells - Prismatic cells have a flat, rectangular shape, making them suitable for space-efficient designs. They are commonly used in smartphones, tablets, and laptops due to their thin and lightweight form. Prismatic cells typically have lower energy density compared to cylindrical cells but are more convenient for certain applications.
- Pouch Cells - Pouch cells are thin, flexible, and lightweight, as they do not have a rigid metal casing. They are often used in applications where space and weight are critical, such as in electric vehicles (EVs) and drones.
2. Battery Modules: Combinations of individual cells, usually connected in series and parallel configurations, with thermal management systems.
3. Battery Packs: Fully assembled and enclosed units comprising multiple modules, designed for specific applications.
4. Battery Management Units (BMUs): Electronic control systems that monitor, manage, and ensure the safety of the entire battery pack.
Each of these components must be tested both separately and assembled.
Battery Trends by Industry
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Automotive
It's important to note that the choice of battery type in the automotive industry depends on the specific vehicle type and application. Conventional ICE vehicles typically use lead-acid batteries for their starting, lighting, and ignition (SLI) needs, while EVs and hybrids rely on more advanced battery technologies like Li-ion and NiMH for their propulsion systems. As technology continues to evolve, there is a growing trend toward using Li-ion and solid-state batteries in electric vehicles, driven by the need for higher energy density, longer driving range, and reduced environmental impact.
Consumer Electronics
Consumer devices, including smartphones, laptops, tablets, digital cameras, and many other portable electronics, typically rely on rechargeable batteries due to their cost-effectiveness and convenience. Other considerations include energy density, form factor, cost, and device-specific requirements. Li-ion batteries are the top choice for most portable electronics due to their high energy density and long cycle life. However, the selection can vary based on the device's intended use, size constraints, and budget considerations.
Medical Devices
The choice of battery type in medical applications depends on factors like energy density, cycle life, safety, and the device's intended use. Safety and regulatory standards, including compliance with medical device directives, play a crucial role in determining the appropriate battery technology for a given medical application. Additionally, considerations such as size, weight, and ease of maintenance may also influence the selection of the best battery type for a specific medical device.
Battery Testing
There are many considerations that need to be made when designing and setting up the test process for battery manufacturing. Safety must always be a top priority considering the high-power ad and high-voltage applications that need to run. Some common battery test cases include:
Voltage Testing
Voltage testing is a fundamental step in battery manufacturing to ensure the quality, performance, and safety of the batteries produced and it covers a lot of ground in battery manufacturing.
It is important to measure the open circuit voltage (OCV) of the battery, which is the voltage when there is no load or current flowing. OCV is a crucial parameter as it provides an indication of the battery's state of charge. It helps ensure that the battery has been properly charged during the manufacturing process. It is important to verify that individual cells within a battery pack have consistent voltage levels. This ensures that they contribute equally to the overall performance of the battery pack.
In a multi-cell battery pack, voltage testing checks for cell balancing. It ensures that none of the cells are overcharged or undercharged, which can lead to issues like reduced capacity, overheating, and reduced battery life. If a cell has a significantly lower or higher voltage than the others, it may indicate a defective cell that should be replaced before further assembly. Voltage testing may also include measuring the battery's voltage while it is under a specific load. This test helps assess the battery's ability to maintain a stable voltage during operation, which is essential for the reliable performance of the battery in its intended application. It is also important to check if the battery's voltage falls within a specified tolerance range. This range is typically defined by the battery's design and the manufacturer's specifications. Deviations from this range may indicate quality issues or defects.
Voltage testing can also verify that safety features like overcharge protection or over-discharge protection are functioning correctly. These features prevent the battery from exceeding safe voltage levels. In some cases, voltage testing may include subjecting the battery to voltage stress tests to simulate real-world conditions. This is especially important for automotive and industrial batteries, where they may experience varying loads and environmental conditions.
Current Testing
Current testing is essential to verify that the battery can reliably deliver the required power and energy for its intended use while maintaining safety and performance standards. Current testing helps determine the battery's capacity, which is its ability to store and deliver energy. By discharging the battery at a specified current rate, the test measures the time it takes for the battery to reach a specific voltage cutoff. The capacity is then calculated based on the discharge time and current, providing information about how much energy the battery can store and deliver.
Current testing assesses the battery's ability to deliver power at different rates. By applying varying discharge rates, manufacturers can evaluate how the battery performs under different load conditions. This is crucial in applications where the battery must provide high power, such as in electric vehicles or power tools. It also measures the voltage response of the battery when subjected to different discharge currents. It checks how the battery voltage changes as it delivers current, ensuring that the voltage remains within acceptable limits for the intended application.
Some batteries, especially in automotive applications, need to handle peak current demands during high-stress situations like starting a vehicle or rapid acceleration. Current testing verifies the battery's ability to deliver these peak currents without issues such as voltage drop or overheating. Like voltage testing, in multi-cell battery packs, current testing verifies that individual cells within the pack contribute equally to the overall current output. An imbalance in current distribution can lead to overloading some cells, reducing battery life.
It is also important to verify that the battery includes overcurrent protection mechanisms and that they are working properly. These mechanisms help prevent damage to the battery and associated equipment in cases of excessive current flow, like short circuits. Additionally, the battery's ability to maintain a stable output current when subjected to varying loads or sudden changes in load must be tested and the temperature changes within the battery must be monitored. Excessive temperature increases can be indicative of inefficiencies or safety concerns.
Capacity Testing
Capacity testing measures the actual amount of energy a battery can store and subsequently release under specific conditions. It primarily involves a discharge test. During this test, the battery is discharged at a controlled current rate, typically referred to as the C-rate. The discharge process continues until the battery's voltage reaches a specified cutoff voltage. Throughout the discharge test, the current flowing from the battery and the time it takes to reach the cutoff voltage are continuously measured. The product of current and time provides the discharge capacity in ampere-hours (Ah) or watt-hours (Wh), depending on the intended application. The measured capacity is compared to the battery's rated or nominal capacity to ensure that it meets the manufacturer's specifications. Any significant deviation from the nominal capacity may indicate a quality issue or potential defect.
Impedance Testing
Impedance testing assesses a battery's internal resistance. High impedance can lead to reduced efficiency and shorter lifespan. Testing involves applying an AC signal to the battery while measuring the voltage and current response. There are several parameters that are measured including:
DC Resistance (R_dc): This measures the direct current (DC) resistance within the battery, which is primarily due to the resistance of the electrolyte, electrodes, and other internal components. Higher DC resistance can indicate issues like electrode degradation or cell aging.
AC Impedance Spectroscopy: By varying the frequency of the AC signal, manufacturers can obtain a detailed impedance spectrum that reveals information about the battery's internal structure, including resistance and capacitance. This method allows for the identification of specific impedance components at different frequencies.
Safety Assessment: Impedance testing is critical for evaluating the safety of batteries, especially in applications where thermal runaway (e.g., in lithium-ion batteries) could lead to safety hazards. High internal resistance or irregular impedance patterns may indicate potential safety risks.
Comparative Testing: Manufacturers can use impedance testing to compare different battery designs, materials, and manufacturing processes to optimize performance and safety.
The results from impedance testing results provide valuable insights into the battery like the State of Health (SoH), State of Charge (SoC) and overall quality.
Cycle Testing
Also known as charge-discharge cycling or cycle life testing, cycle testing simulates charging and discharging cycles to evaluate a battery's long-term performance and durability. During cycle testing, the battery is subjected to a predefined pattern of charging and discharging cycles. The pattern can vary depending on the intended application and manufacturer's specifications. Several parameters are monitored during cycle testing, including voltage, current, temperature, capacity and internal resistance.
The primary goal of cycle testing is to determine the battery's cycle life, which is the number of charge and discharge cycles it can endure while maintaining specified performance and capacity levels. The battery's cycle life can vary significantly based on its chemistry, design, and the depth of discharge during each cycle. This can reveal how and when a battery fails. Failures may include reduced capacity, increased internal resistance, or safety issues such as thermal runaway. Understanding failures is the most effective way to improve battery designs and identify potential issues early in the manufacturing process. The data is also used to help set warranty terms and to assure customers of the battery's long-term reliability.
Testing at the Component Level
Understanding the nuances of testing battery cells, modules, packs, and BMUs is crucial for ensuring product quality, performance, and safety. Automated testing equipment, environmental chambers, and advanced data acquisition systems are integral to this process, providing the precision and repeatability needed to meet stringent quality standards in the battery manufacturing industry.
Cell-Level Testing
Battery cell testing focuses on individual cells before integration into larger modules or packs. This early-stage testing helps identify defective or subpar cells.
Cell testing typically includes:
- Voltage - Measured under various load conditions.
- Capacity - Determining the energy storage capability.
- Internal Resistance - Indicating cell health and performance.
- Cycle Life - Estimating the number of charge and discharge cycles the cell can endure.
Module-Level Testing
Battery module testing verifies the performance and safety of a group of cells assembled into a module. It includes tests like thermal profiling, electrical characterization, and impact testing.
Key considerations for module testing include:
- Balancing - Ensuring uniform charge and discharge among cells.
- Thermal Management - Monitoring and controlling temperature within the module.
- Safety Mechanisms - Testing safety features, like thermal cutoffs.
Pack-Level Testing
Battery pack testing evaluates the overall performance and safety of a complete battery system, often subjecting it to rigorous conditions to simulate real-world usage.
Test scenarios for pack testing in the lab includes:
- Environmental Testing - Evaluating performance in extreme temperatures, humidity, and altitude.
- Abuse Testing - Simulating physical damage, overcharging, and short circuits.
- Life-Cycle Testing - Assessing long-term durability and reliability under operational conditions.
Test scenarios for pack testing in production includes:
- Charge-discharge or micro-cycles
- Safety Components – Examples include interlock, shut down signals, etc…
- Insulation Resistance and Dialectic Strength Test
- Thermal Profile
- OCV and SoC
BMU Testing
BMUs play a pivotal role in monitoring and managing the health and safety of battery packs. Testing BMUs ensures their accuracy and reliability.
The following functional and stress tests ensure that BMUs function as intended, accurately monitor and protect the battery pack, and maintain the safety and reliability of the overall battery system:
- State-of-Charge (SOC) and State-of-Health (SOH) Estimation - Verify that the BMU accurately estimates the SOC and SOH of the battery pack under various operating conditions.
- Cell Balancing - Ensure that the BMU can actively balance the cells within the battery pack, preventing overcharging or discharging of individual cells.
- Voltage Monitoring - Confirm that the BMU accurately measures and monitors the voltage of each cell within the battery pack.
- Current Measurement - Verify that the BMU accurately measures the current flowing in and out of the battery pack during charging and discharging.
- Temperature Monitoring - Test the BMU's ability to monitor and respond to temperature variations within the battery pack, ensuring safe operation.
- Overcharge and Overdischarge Protection - Ensure the BMU activates protective mechanisms to prevent overcharging or overdischarging, which can damage the battery cells.
- Insulation Resistance and Dialectic Strength Test
- Fault Detection and Reporting - Test the BMU's ability to detect faults, such as short circuits or high-temperature conditions, and report these issues for appropriate action.
- Communication Interface - Verify that the BMU can communicate with external systems, such as vehicle controllers or charging infrastructure, using standard communication protocols like Controller Area Network (CAN) or others.
- Cell Authentication - Test the BMU's ability to verify the authenticity and integrity of the battery cells to prevent counterfeit or unsafe replacements.
- Stress Tests: Including overcharge, overdischarge, thermal stress, vibration and shock, EMI/EMC (electromagnetic interference electromagnetic compatibility), load testing, and environmental testing.
Maximizing your Battery Test Equipment Investment
There are 5 secrets to any smart test equipment investment: automation, modularity, scalability, flexibility, and standardization. This is particularly true in the case of battery development and manufacturing. As the industry evolves, the technologies continue to change. Investing in equipment that can be adapted to the product reduces material cost and operator intervention. You should consider:
- Automation – Remove subjectivity and redundant operator intervention while speeding up processes for highly accurate results.
- Modularity – As requirements change, equipment and coding must change with it. When working within smaller changeable blocks, no time is wasted re-inventing the wheel.
- Scalability - As demand for a product grows and decreases, a scalable system has the ability to accommodate what the customers need, when they need it.
- Flexibility – Going and in with both modularity and scalability, it’s the flexibility of the test design that allows for smart and cost-effective modifications.
- Standardization – By sharing common test equipment throughout company locations and departments, every employee speaks the same language. From R&D through to repair, results become consistent across the board, and training or ramp up time becomes significantly reduced.
A best practice for battery test is to leverage an industry established common platform like Batterie Inspektor™. 
With a wide range of test parameters, Batterie Inspektor™ ensures top quality products including cells, modules, BMUs and packs, at every stage of manufacturing. Its smart, modular and scalable design allows you to build the solution that best fits and grows with your manufacturing requirements from a single source. It improves product performance with flexible automation, sustainable retrofitting, and smart data management.
As opposed to starting from scratch, an existing platform quickly reduces the non-recurring engineering (NRE) fees, which can be a large bulk of the cost. There is also the comfort and security of the reliability of a known brand.
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