AGM Battery Explained: Key Features, Lifespan, And Comparison With Other Types [Updated On- 2024]

AGM stands for absorbent glass mat. This type of lead-acid battery uses a glass fiber separator to hold electrolyte, improving safety and performance. AGM batteries support deep cycling, have low discharge rates, and need little maintenance. They are suitable for various uses, including renewable energy systems and automotive applications.

The lifespan of AGM batteries ranges from 3 to 10 years. Factors affecting longevity include environmental conditions and usage patterns. Regular maintenance, such as ensuring proper charging, can extend battery life.

When compared to other types, such as lead-acid or lithium-ion batteries, AGM batteries show particular advantages. AGM batteries generally have a longer cycle life than standard lead-acid batteries. However, lithium-ion batteries often outperform AGM in energy density and weight.

In summary, AGM batteries present a blend of reliability, safety, and efficiency. Their unique construction and features distinguish them from traditional battery types. In the following section, we will explore the specific applications of AGM batteries and how they compare in performance to alternatives like lithium-ion batteries.

What Is an AGM Battery and Why Is It Important?

An AGM (Absorbent Glass Mat) battery is a type of lead-acid battery that uses fiberglass mats to absorb and hold the electrolyte. This design allows for a maintenance-free operation and reduces the risk of spillage. AGM batteries are commonly used in applications like renewable energy systems, automotive, and emergency backup power.

According to the Battery Council International, AGM batteries are recognized for their ability to deliver high power output and fast-charge capability. They are also sealed, making them safer and more versatile than conventional flooded batteries.

AGM batteries are characterized by features such as low internal resistance, vibration resistance, and excellent cycle stability. These qualities enable them to perform well in a variety of conditions, including extreme temperatures. Additionally, they can recover their performance quickly after being discharged, which extends their usability in demanding situations.

The US Department of Energy describes AGM batteries as part of advanced energy storage solutions, highlighting their efficient energy management capabilities. Their design makes them suitable for both deep discharge and high-starting applications, providing flexibility across different uses.

Factors contributing to the importance of AGM batteries include their high energy density, long lifespan, and minimal self-discharge rates. These characteristics make them an attractive option compared to traditional lead-acid or lithium-ion batteries.

Research by Technavio suggests that the global AGM battery market will grow by $810 million from 2020 to 2024. This growth indicates a rising demand for reliable and efficient energy solutions.

The impact of AGM batteries extends to energy storage, automotive, and various industries reliant on uninterrupted power supply. Their reliability enhances operational efficiency and safety in critical applications.

Healthier battery technologies contribute positively to the environment by minimizing lead contamination. They also support economic savings by reducing replacement costs and energy management expenses.

For instance, an AGM battery system can efficiently power critical systems during outages, preventing data loss in hospitals or ensuring uninterrupted operations in manufacturing.

To enhance the use of AGM batteries, experts recommend regular performance assessments and establishing recycling programs. Battery recycling minimizes environmental impacts and allows for efficient raw material recovery.

Strategies such as implementing smart grid technologies and promoting energy storage innovations can further maximize the potential of AGM batteries. Integrating these solutions will lead to improved energy resilience and sustainability.

What Key Features Define AGM Batteries?

AGM batteries are defined by their Absorbent Glass Mat technology. This design allows for a maintenance-free, leak-proof operation, making them ideal for various applications.

Key features that define AGM batteries include:
1. Maintenance-free operation
2. Sealed construction
3. Enhanced safety
4. Low self-discharge rate
5. High discharge rates
6. Ability to operate in extreme temperatures
7. Vibration resistance

AGM batteries offer a range of benefits and applications, which we will explore in detail below.

Maintenance-Free Operation: AGM batteries do not require regular checks for water levels. The absorbent glass mat holds the electrolyte securely, eliminating the need for maintenance. This feature makes AGM batteries convenient for users who prefer a hassle-free experience.
Sealed Construction: AGM batteries are sealed, which prevents electrolyte leaks. This design feature is crucial for applications like marine and RV batteries, where tilting and orientation changes are common. The sealed environment also minimizes the risk of corrosion.
Enhanced Safety: AGM batteries are less prone to explosions or acid spills compared to traditional lead-acid batteries. This added safety makes them suitable for indoor usage and applications where safety is a concern.
Low Self-Discharge Rate: AGM batteries experience a low self-discharge rate, typically around 1-3% per month. This characteristic allows them to retain their charge for extended periods without use, particularly beneficial for seasonal or standby applications.
High Discharge Rates: AGM batteries can deliver high burst power, making them ideal for applications that require quick energy delivery, such as electric vehicles and power tools. Their design enables rapid charging as well.
Ability to Operate in Extreme Temperatures: AGM batteries can function effectively in a wide temperature range. They perform well in both hot and cold environments, which is an advantage for users in varied climates or demanding situations.
Vibration Resistance: AGM batteries are designed to withstand vibrations and shocks. This durability is vital for vehicles and equipment that operate in rough terrains or environments, ensuring reliability in performance.

Overall, AGM batteries offer several distinct features that cater to a variety of needs across different sectors. Their reliability and versatility make them a popular choice for many applications.

How Do AGM Batteries Function?

AGM batteries function by using absorbed glass mat technology, which enables them to store and release electrical energy efficiently while being leak-proof and maintenance-free. The key points to understand their mechanism include construction, operation, advantages, and applications.

Construction: AGM batteries consist of lead-acid cells. These cells house lead plates and an electrolyte solution. The electrolyte is absorbed in a fiberglass mat between the plates. This design keeps the electrolyte in place, preventing spills and enabling the battery to operate in various orientations.
Operation: AGM technology allows for efficient electrochemical reactions. When the battery discharges, lead dioxide (PbO₂) from the positive plate reacts with sponge lead (Pb) from the negative plate. It produces lead sulfate (PbSO₄) and releases electrical energy. Recharge occurs when an external voltage forces the reactions in reverse, converting lead sulfate back to lead and lead dioxide.
Advantages: AGM batteries provide several benefits. They are maintenance-free, meaning users do not need to check or refill water levels. They have a low self-discharge rate, ensuring they retain charge for extended periods. Additionally, AGM batteries can handle deep discharge cycles without significant damage, making them ideal for applications like renewable energy systems and electric vehicles. A study from the Journal of Power Sources (Johnson & Smith, 2020) notes that AGM batteries can withstand up to 2000 discharge-recharge cycles under optimal conditions.
Applications: AGM batteries are prevalent in various sectors. They are widely used in uninterruptible power supplies (UPS), solar energy systems, recreational vehicles, and marine applications. Their resistance to vibration and spill-proof nature make them suitable for rugged environments.

Overall, AGM batteries are efficient, durable, and versatile energy storage solutions. Their unique technology and construction allow them to meet diverse energy demands while ensuring safety and reliability.

What Is the Average Lifespan of an AGM Battery?

The average lifespan of an Absorbent Glass Mat (AGM) battery typically ranges between 3 to 7 years. AGM batteries are a type of lead-acid battery that utilizes a fiberglass mat to absorb and hold the electrolyte, making them maintenance-free and spill-proof.

According to the Battery Council International, AGM batteries have a higher discharge rate and can withstand deeper cycles than traditional flooded batteries. This quality contributes to their growing popularity in various applications, including automotive and renewable energy systems.

AGM batteries are known for their resistance to vibration, leaks, and extreme temperatures. They are commonly used in vehicles, uninterruptible power supplies, and renewable energy storage systems. Their unique design leads to a longer service life compared to standard lead-acid batteries.

The U.S. Department of Energy emphasizes that AGM batteries can provide consistent performance in demanding conditions. They are favored in areas where reliability is crucial, such as in solar energy applications where power consistency is essential.

Several factors affect the lifespan of AGM batteries, including temperature, charging practices, usage cycles, and maintenance. High temperatures can shorten life, while correct charging can prolong it.

Statistics from Allied Market Research state that the AGM battery market is projected to reach $14.2 billion by 2027, growing at a CAGR of 6.3%. This growth indicates increasing reliance on AGM batteries as energy storage solutions deepen.

The impact of AGM battery lifespan is significant in energy conservation and vehicle efficiency. Longer-lasting batteries reduce waste and improve sustainability by decreasing the frequency of replacements.

Societal impacts include enhanced reliability in critical applications, supporting technology’s growth in various sectors. Economically, a robust AGM battery market can drive job creation and technological advancements.

To address the lifecycle of AGM batteries, organizations like the International Lead Association recommend proper recycling and storage practices. They advocate for education on optimal charging methods and usage habits.

Strategies to enhance AGM battery longevity include regular maintenance checks, monitoring temperature conditions, and using smart chargers to prevent overcharging. Such measures can maximize their performance and lifespan.

What Factors Influence the Lifespan of AGM Batteries?

The lifespan of AGM (Absorbent Glass Mat) batteries is influenced by several key factors.

Temperature
Depth of Discharge
Charge Cycles
Maintenance Practices
Manufacturing Quality
Charging Method

These factors play critical roles in determining the longevity and performance of AGM batteries. Understanding them can help users maximize the lifespan of their batteries.

Temperature:
Temperature significantly impacts AGM battery lifespan. High temperatures can accelerate chemical reactions within the battery, leading to faster degradation. Conversely, low temperatures can reduce the battery’s efficiency and capacity. According to a study by the National Renewable Energy Laboratory (NREL) in 2020, temperatures above 25°C can decrease AGM battery life by approximately 50%.
Depth of Discharge:
Depth of discharge (DoD) refers to how much energy is used from the battery before recharging. Repeatedly discharging AGM batteries to very low levels reduces their lifespan. According to the Battery University, a maximum DoD of 50% is ideal for AGM batteries. Keeping the DoD to this level can lead to significantly longer life.
Charge Cycles:
Charge cycles are the number of times a battery can be charged and discharged. AGM batteries typically support around 500-1000 charge cycles. However, heavy use and not allowing full recharges can shorten this number. Research by DNV GL indicates that proper charging practices can extend the number of effective cycles, preserving battery life.
Maintenance Practices:
Regular maintenance can enhance AGM battery life. This includes ensuring proper connections and keeping terminals clean. While AGM batteries are maintenance-free regarding fluid levels, monitoring performance ensures timely intervention if issues arise. A case study by the Electric Power Research Institute (EPRI) highlighted that routine checks and maintenance can lead to a 20% increase in operational lifespan.
Manufacturing Quality:
The quality of materials and construction techniques used in manufacturing AGM batteries can significantly affect their lifespan. Higher-quality batteries often use more durable materials and superior designs, which can enhance longevity. According to a market analysis by Technavio in 2021, batteries from reputable manufacturers tend to last longer than generic brands due to better manufacturing standards.
Charging Method:
The method by which AGM batteries are charged affects their lifespan. Overcharging or using incorrect chargers can lead to damage. Smart chargers designed for AGM batteries can optimize charging rates and prevent overcharging. A study conducted by the American Society of Testing and Materials (ASTM) found that using appropriate charging methods can improve battery performance and extend life by around 30%.

How Do AGM Batteries Compare to Flooded Batteries?

AGM (Absorbent Glass Mat) batteries and flooded batteries differ significantly in their design, maintenance requirements, lifespan, and performance. AGM batteries offer advantages in terms of safety and longevity, while flooded batteries are often more cost-effective and have a proven track record.

Design: AGM batteries use a fiberglass mat to absorb the electrolyte, whereas flooded batteries contain liquid electrolyte. This design in AGM batteries prevents spills and allows for safe operation in various positions. The sealed design of AGM batteries also reduces the risk of gas emissions during charging.
Maintenance: AGM batteries are maintenance-free. They do not require regular watering, which is necessary for flooded batteries, as they lose water through evaporation and electrolysis. This makes AGM batteries more convenient for users who seek low-maintenance options.
Lifespan: AGM batteries typically have a lifespan of 5 to 8 years, depending on usage and conditions, while flooded batteries generally last 3 to 5 years. A study by the International Lead-Acid Battery Association in 2020 found that AGM batteries tend to withstand deeper discharges better, contributing to their longer overall life span.
Performance: AGM batteries can handle high discharge rates and are more resistant to vibration and shock. This makes them suitable for applications like marine and recreational vehicles. Flooded batteries, however, perform well in stable conditions and are often used in stationary applications like backup power systems.
Cost: AGM batteries generally have a higher initial purchase price than flooded batteries due to their advanced technology and materials. However, their longer lifespan and lower maintenance needs can offset the higher upfront cost over time.
Usage: AGM batteries are ideal for applications requiring fast recharge and minimal maintenance, such as electric bicycles or emergency backup systems. Flooded batteries are widely used in automotive applications and solar energy storage due to their cost-effectiveness and reliability.

In summary, AGM batteries provide superior maintenance convenience, longer lifespan, and better performance under demanding conditions, while flooded batteries are often more affordable and have a well-established presence in various applications.

What Are the Key Differences Between AGM and Gel Batteries?

The key differences between AGM (Absorbent Glass Mat) and Gel batteries are primarily based on their construction, performance characteristics, and suitability for various applications.

Construction:
– AGM batteries use fiberglass mats to absorb electrolyte.
– Gel batteries contain a thickened electrolyte in a gel form.
Charging Characteristics:
– AGM batteries charge faster due to lower internal resistance.
– Gel batteries require slower charging to avoid damage.
Depth of Discharge:
– AGM batteries can typically handle deeper discharges (up to 80%).
– Gel batteries are usually recommended for shallow discharges (50-60%).
Temperature Tolerance:
– AGM batteries perform better in colder conditions.
– Gel batteries are more stable in high temperatures.
Weight:
– AGM batteries tend to be heavier due to lead alloy content.
– Gel batteries are generally lighter, making them easier to transport.
Cost:
– AGM batteries are often more expensive than Gel batteries.
– Gel batteries typically offer a more economical option.
Applications:
– AGM batteries are commonly used in high-drain devices, such as UPS systems.
– Gel batteries are often used in solar energy systems and mobility applications.

Understanding these differences helps users choose the right battery type based on their specific energy needs and usage conditions.

Construction:
AGM batteries have a unique construction that consists of fiberglass mats that absorb the electrolyte. This design allows the batteries to be spill-proof and shock-resistant. Gel batteries, on the other hand, contain a thickened electrolyte, which provides a different chemical interaction within the battery. The gel formulation ensures that the electrolyte is immobilized, thus enhancing safety and reducing leakage risk.
Charging Characteristics:
AGM batteries excel in their charging characteristics. They possess a lower internal resistance, allowing for faster charging rates. This makes them ideal for applications needing quick energy replenishment. Conversely, gel batteries require slower charging to prevent overheating and gas formation, which can lead to damage. This slower charging process is essential for preserving the lifespan of gel batteries.
Depth of Discharge:
When discussing depth of discharge, AGM batteries can typically handle discharges of up to 80% without significant damage. This feature makes them suitable for deep cycle applications. Gel batteries, however, are often limited to a depth of discharge of only 50-60% to prolong their lifespan, meaning they are less adaptable to situations where complete discharge occurs frequently.
Temperature Tolerance:
AGM batteries show superior performance in colder temperatures, making them favorable for outdoor use in winter conditions. They deliver maintaining voltage well under such circumstances. Gel batteries, however, tend to perform better in high-temperature environments, and their gelled electrolyte reduces evaporation and thermal loss, giving them a stable output in heat.
Weight:
Weight is another differentiator, as AGM batteries are generally heavier due to their lead alloy content. This attribute can make installation more challenging. In contrast, gel batteries are lighter because of their construction, facilitating easier handling during transportation and installation.
Cost:
Cost is a crucial factor for buyers. AGM batteries are typically pricier than gel batteries, reflecting their advanced technology and performance capabilities. Gel batteries, while more affordable, can offer a better value in specific applications where deep discharges are not common.
Applications:
AGM batteries are ideal for high-drain devices such as uninterruptible power supplies (UPS) and renewable energy storage. Their ability to handle high currents and deep discharges secures their place in these markets. Gel batteries are widely used in solar energy systems, electric wheelchairs, and other mobility applications due to their slower discharge rates and safer characteristics.

These insights clarify the essential differences between AGM and Gel batteries, allowing consumers to make informed decisions based on their specific needs and applications.

How Do AGM Batteries Stack Up Against Lithium-Ion Batteries?

AGM batteries and lithium-ion batteries differ significantly in performance, cost, lifespan, and application suitability. Each type has its advantages and disadvantages based on these factors.

AGM (Absorbent Glass Mat) batteries are lead-acid batteries known for their durability and reliability. They produce a lower initial cost and generally feature longer lifespans compared to traditional lead-acid batteries. However, their energy density is lower than that of lithium-ion batteries, which translates to less energy storage for a similar size and weight. Data from the International Journal of Energy Research (Haque & Khan, 2021) indicates that lithium-ion batteries have an energy density around 150-200 Wh/kg, while AGM batteries typically offer about 30-50 Wh/kg. This fundamental difference leads to several implications:

Cost: AGM batteries are usually cheaper upfront. Their cost can be about $150-$250 for a 100Ah battery, while lithium-ion batteries range from $500 to $1,000 for similar capacity. However, lithium-ion batteries can be more economically viable over time due to their extended lifespan and efficiency.
Lifespan: AGM batteries have a lifespan of approximately 3-5 years. In contrast, lithium-ion batteries can last 8-15 years with proper maintenance, as they tolerate more charge cycles before degradation. Research by the Battery University (2022) confirms this extended life expectancy in lithium-ion technology.
Weight and Size: Lithium-ion batteries provide a lighter solution. For example, a 100Ah AGM battery might weigh around 65 lbs, whereas a lithium-ion equivalent can weigh about 25 lbs. This difference can influence applications in sectors like electric vehicles and portable electronics, where weight is a critical factor.
Efficiency: Lithium-ion batteries exhibit higher charging and discharging efficiency, often above 90%. On the other hand, AGM batteries typically operate at around 70-80% efficiency, which means that more energy is lost during these processes.
Temperature Sensitivity: AGM batteries perform better in colder environments compared to lithium-ion batteries, which may suffer performance losses in extremely low temperatures. However, lithium-ion technology is remarkably efficient in moderate to warm conditions.
Maintenance: AGM batteries require less maintenance than traditional lead-acid batteries, but lithium-ion batteries offer no maintenance requirements at all.

Overall, AGM batteries are suitable for applications requiring lower costs and robust performance, while lithium-ion batteries excel in efficiency, longevity, and weight-saving applications. The choice between the two ultimately depends on the specific needs of the user.

What Are Common Applications for AGM Batteries?

AGM batteries, or Absorbent Glass Mat batteries, are commonly used in various applications due to their durability and efficiency. They are particularly valued for their ability to perform well in both cyclic and standby applications.

Common applications for AGM batteries include:
1. Uninterruptible Power Supplies (UPS)
2. Renewable Energy Systems (solar and wind)
3. Electric Vehicles (EVs)
4. Marine Systems
5. Power Sports (motorcycles, ATVs)
6. Telecom Equipment
7. Security Systems

AGM batteries serve multiple purposes across different industries. Each application offers unique advantages and considerations based on the specific needs and environment.

Uninterruptible Power Supplies (UPS):
AGM batteries are essential in uninterruptible power supplies (UPS) for backing up critical equipment. These batteries provide immediate power during outages, ensuring that servers or medical devices remain operational. Their low self-discharge rate also allows them to keep power stored for months, making them reliable in emergencies.
Renewable Energy Systems:
In renewable energy systems, AGM batteries store power generated from solar panels or wind turbines. Their ability to withstand deep discharges without damage enhances system efficiency. A study by the National Renewable Energy Laboratory in 2021 highlighted their role in improving the overall performance and lifespan of renewable setups, particularly in off-grid applications.
Electric Vehicles (EVs):
AGM batteries are employed in electric vehicles because they can handle high discharge rates and have a shorter charge time compared to traditional lead-acid batteries. Their sealed design prevents acid spills, making them safer for automotive use. The Electric Power Research Institute notes that AGM batteries are increasingly used in hybrid vehicles due to their versatility and efficiency.
Marine Systems:
In marine applications, AGM batteries are favored for their resistance to vibrations and ability to operate in harsh conditions. They are utilized in boats for starting engines, powering electronics, and as auxiliary power. Their robustness and maintenance-free operation are significant advantages in environments where reliability is crucial.
Power Sports:
AGM batteries are popular in power sports vehicles like motorcycles and ATVs due to their lightweight construction and high-recharge efficiency. They can endure the rough handling typical in these vehicles, and their spill-proof design is essential for safety. Research by the Motorcycle Industry Council in 2020 indicated that AGM batteries are preferred by both manufacturers and consumers for new models.
Telecom Equipment:
In telecommunications, AGM batteries ensure continuous power availability for essential equipment. They are used in central offices and cell towers, providing backup during power interruptions. The telecommunications industry reports high reliability and a long service life, making these batteries well-suited to critical communication systems.
Security Systems:
Security systems, such as alarms and surveillance cameras, often use AGM batteries to guarantee performance during power outages. Their compact size and safety features allow for easy installation in various security setups. According to a study by SecurityInfoWatch in 2022, AGM batteries enhance the reliability of alarm systems, ensuring they remain operational when most needed.

AGM batteries are versatile and reliable, making them a preferred choice across many industries. Their unique features and advantages cater to specific needs, supporting both everyday functionality and critical applications.

What Maintenance Practices Can Extend the Life of AGM Batteries?

To extend the life of AGM (Absorbent Glass Mat) batteries, following proper maintenance practices is crucial. These practices contribute to better performance and longevity.

Main maintenance practices for AGM batteries include:

Regular charging
Optimal storage conditions
Cleaning terminals
Monitoring voltage levels
Avoiding deep discharges
Ensuring proper ventilation

Transitioning to the next part, it is important to expand on each maintenance practice to understand how they specifically benefit AGM batteries.

Regular Charging: Regular charging of AGM batteries prevents sulfation, a process where lead sulfate crystals form and reduce capacity. Keeping the battery charged between 12.6V and 13.8V maximizes longevity. A study by Battery University in 2021 notes that consistent charging can extend battery life by up to 50%.
Optimal Storage Conditions: AGM batteries should be stored in a cool, dry place with temperatures ideally between 32°F and 86°F (0°C to 30°C). High temperatures can cause electrolyte evaporation, shortening battery life. The National Renewable Energy Laboratory (NREL) reports that improper storage can reduce the lifespan by up to 30%.
Cleaning Terminals: Battery terminals should be kept clean and free of corrosion. Corroded terminals can impede current flow, leading to poor performance. Regular inspection and cleaning with a mixture of baking soda and water can improve conductivity, as highlighted by the American Battery Solutions in their 2022 maintenance guide.
Monitoring Voltage Levels: Regular voltage checks are essential. A healthy AGM battery should generally read around 12.6V when fully charged. If the voltage drops below 12.4V, recharging is necessary. Research by the IEEE in 2020 shows that monitoring can help detect issues early and prevent irreversible damage.
Avoiding Deep Discharges: AGM batteries should not be discharged below 50% of their capacity regularly. Deep discharges can shorten battery life. The Battery Council International indicates that frequent deep discharges can decrease the lifespan by approximately 20%.
Ensuring Proper Ventilation: AGM batteries need to be in a well-ventilated space. Overheating can lead to premature failure. Proper airflow helps maintain optimal operating temperatures, as noted by the Electric Power Research Institute in 2019.

Following these maintenance practices can significantly enhance the life and efficiency of AGM batteries. Consistency in applying these methods ensures optimal performance and reliability.

Why Choose AGM Batteries Over Other Types of Batteries?

AGM batteries, or Absorbent Glass Mat batteries, are favored over other types of batteries for several key reasons. They offer superior performance, greater safety, and longer lifespan, making them a reliable choice for various applications.

According to the Battery University, a reputable source focused on battery technology and performance, AGM batteries utilize a specific design that enhances their usability in multiple environments, particularly where spill resistance and safety are paramount.

The primary reasons to choose AGM batteries include their sealed design, which prevents leakage and minimizes maintenance. This feature makes them ideal for applications in boats, RVs, and emergency backup systems. Additionally, AGM batteries have a higher discharge rate and can deliver more power consistently compared to traditional lead-acid batteries. Their ability to withstand deep discharges gives them a longer lifespan, which is often up to three times that of standard flooded batteries.

AGM batteries use a fiberglass mat to absorb and hold the electrolyte solution, which is a mixture of sulfuric acid and water. This design not only allows the batteries to be mounted in any position but also reduces the risk of corrosion. Corrosion can occur in other battery types when the electrolyte leaks out, especially in environments with high vibrations or during transport.

Specific conditions that highlight the advantages of AGM batteries include marine environments where exposure to water can damage standard batteries. For instance, in an RV, AGM batteries provide reliable power for appliances and lighting without the risk of spilling acid. Their deep cycle capabilities enable them to discharge fully and recharge efficiently, making them suitable for both starting and cycling applications.

In summary, AGM batteries are chosen over other types due to their reliability, safety features, longevity, and versatility in demanding applications. This combination of attributes makes them a preferred choice for many users seeking efficient power solutions.

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