Guide to Common Battery Terminology


Batteries are ubiquitous today, powering everything from smartphones to electric vehicles. We must familiarize ourselves with the common battery terminology to better understand these powerhouses. This comprehensive guide will explore the various types of batteries, their components, performance metrics, charging and discharging processes, battery connections, and safety and maintenance considerations. Let’s start!

lithium battery internal structure diagram

Part 1. Battery types

Lead-Acid Battery

Lead-acid batteries are one of the oldest and most widely used battery types. They consist of lead plates immersed in an electrolyte solution of sulfuric acid. Typical applications for these batteries include automobiles, uninterruptible power supplies (UPS), and other systems that demand reliable energy storage.

Lithium-Ion Battery

Lithium-ion batteries have revolutionized portable electronics and electric vehicles. They employ lithium compounds as the active material in their electrodes. Lithium-ion batteries offer high energy density, longer cycle life, and lighter weight than other battery types, making them a popular choice for various devices.

Nickel-Cadmium Battery (NiCd)

Nickel-cadmium batteries, known as NiCd batteries, feature nickel oxide hydroxide, and metallic cadmium electrodes. They have a good cycle life and perform well in extreme temperatures, making them suitable for cordless power tools and emergency lighting applications.

Nickel-metal hydride Battery (NiMH)

Nickel-metal Hydride or NiMH batteries use a hydrogen-absorbing alloy instead of cadmium. They provide higher energy density than Ni-Cd batteries, making them preferable for hybrid vehicles, digital cameras, and portable electronic devices.

Alkaline Battery

Alkaline batteries are a common choice for everyday devices such as remote controls, flashlights, and toys. They employ manganese dioxide as the positive and zinc-based negative electrodes, with an alkaline electrolyte solution. Alkaline batteries offer a longer shelf life and better performance than zinc-carbon batteries.

Zinc-Carbon Battery

Zinc-carbon batteries, known as dry-cell batteries, are inexpensive and widely available. They utilize a zinc anode and a carbon rod surrounded by a manganese dioxide cathode. Although they have lower energy capacity and shorter lifespans compared to alkaline batteries, zinc-carbon batteries are suitable for low-power devices and temporary applications.

Rechargeable Battery

Rechargeable batteries, as the name suggests, can be recharged multiple times. They come in various chemistries, including lithium-ion, nickel-cadmium, and nickel-metal hydride. Rechargeable batteries provide cost-effective and environmentally friendly power solutions for devices requiring frequent or prolonged use.

Non-Rechargeable Battery

Non-rechargeable batteries, also known as primary batteries, are designed for single use. Once depleted, users cannot recharge them and must replace them. Non-rechargeable batteries commonly power devices where frequent battery replacements are not practical or feasible.

Part 2. Battery components

lithium ion battery

To understand how batteries work, let’s explore their key components:


Batteries consist of two electrodes: the anode and the cathode. The anode is the negative electrode, where oxidation occurs during discharge. At the same time, the cathode is the positive electrode, where reduction takes place.


The electrolyte acts as a medium that allows the movement of ions between the electrodes. It facilitates the chemical reactions necessary for energy storage and release within the battery.


The anode is the electrode where oxidation occurs during the battery’s discharge cycle. It releases electrons and ions into the electrolyte, generating the flow of electric current.


The cathode is the electrode where reduction takes place during discharge. It accepts the electrons and ions from the electrolyte, completing the electric circuit.


The separator is a porous material placed between the anode and cathode to prevent electrical short circuits while allowing the passage of ions.


Terminals are the external connection points of a battery, allowing for the transfer of electrical current to external devices or charging sources.


The casing houses and protects the battery’s internal components, providing structural integrity and insulation.

A cell refers to the basic unit of a battery. It consists of electrodes, an electrolyte, and a separator. Multiple cells can be connected to form a higher voltage or capacity battery.

Part 3. Battery performance metrics

Several vital metrics are crucial for evaluating battery performance:


Capacity represents the amount of electrical energy a battery can store and deliver. Typically, we measure it in ampere-hours (Ah) or milliampere-hours (mAh). Higher capacity batteries provide more extended operating times.


Voltage is the electrical potential difference between the battery’s positive and negative terminals. It determines the force at which electrons flow through a circuit. We commonly measure battery voltage in volts (V).


Current denotes the flow of electric charge in a circuit and is measured in amperes (A). It represents the rate at which electrons move through the circuit.

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Energy density indicates the amount of energy a battery can store per unit of its volume or mass. We express it in watt-hours per liter (Wh/L) or kilogram (Wh/kg). Batteries with higher energy density offer more excellent energy storage capabilities.

Power Density

Power density refers to the amount of power a battery can deliver per unit of its volume or mass. We measure it in watts per liter (W/L) or kilogram (W/kg). Batteries with higher power density can supply more power in a shorter period.

Cycle Life

Cycle life refers to the number of charge and discharge cycles a battery can undergo before its capacity significantly degrades. A longer cycle life indicates better durability and longevity.

Self-Discharge Rate

Self-discharge rate represents the rate at which a battery loses its charge over time when unused. Batteries with low self-discharge rates retain their charge for extended periods, ensuring they are ready for use when needed.


Efficiency measures how effectively a battery converts stored energy into usable electrical energy. Higher efficiency means less energy loss during charging and discharging processes.

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Internal resistance characterizes the opposition to the flow of electrical current within a battery. Batteries with low internal resistance can deliver currents more efficiently.


The C-rating indicates a battery’s discharge rate relative to its capacity. For example, a battery with a 1C rating can discharge its entire capacity in one hour. Higher C-ratings allow for faster discharge rates.

Amps (Amperes)

The unit of electric current represents the rate of flow of electric charge. It measures the current flow through a circuit at a given moment.


A unit of electric charge represents the amount of electrical energy transferred by a current of one ampere flowing for one hour. People commonly use it to measure the capacity of a battery to store energy.


The unit of power represents the rate at which work or energy transfers. You calculate it by multiplying voltage by current.


This unit of energy represents the energy consumed or produced by a device with a power rating of one watt operating for one hour. People commonly use it to measure a battery’s energy capacity or an electrical device’s energy consumption over time.

Part 4. Charging and discharging

lithium-ion battery charging curve

Understanding the charging and discharging processes is essential for maintaining battery performance:


Charging involves supplying electrical energy to a battery to restore its capacity. Proper charging techniques and voltage levels are crucial to ensure battery longevity and safety.


Discharging refers to releasing stored electrical energy from a battery to power external devices. The discharge rate should be within the battery’s specified limits to maintain optimal performance.


Overcharging occurs when someone charges a battery beyond its recommended capacity or voltage. This can lead to reduced battery life, increased heat generation, and even safety hazards.

Deep Discharge

Deep discharge occurs when someone discharges a battery to deficient voltage levels. This can cause irreversible damage, reducing the battery’s capacity and lifespan.

Trickle Charging

Trickle charging is a low-current method used to maintain batteries at total capacity during extended periods of inactivity or storage. It prevents self-discharge and keeps the battery ready for use.

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Fast charging techniques allow rapid replenishment of a battery’s capacity, significantly reducing charging times. However, if not implemented correctly, fast charging may generate more heat and impact long-term battery health.

Float Charging

Float charging involves maintaining a battery at a constant voltage level, typically lower than its full charge voltage. People commonly use it in applications where batteries need to be constantly available, such as emergency backup systems.

Battery Management System (BMS)

A battery management system is an electronic system that monitors and controls various aspects of battery operation, including charging, discharging, and temperature regulation. It ensures optimal performance, safety, and longevity of the battery.

Part 5. Battery connections

Battery connections play a crucial role in achieving desired voltage and capacity levels:

Serial Connection

Serial or series connections involve connecting batteries in a chain-like configuration. The positive terminal of one battery is connected to the negative terminal of the next battery, increasing the overall voltage while keeping the capacity unchanged.

Parallel Connection

Parallel connection involves connecting batteries side by side, with their positive and negative terminals connected. This configuration increases the overall capacity while maintaining the voltage level.

Series-Parallel Connection

Series-parallel connection combines both series and parallel connections to achieve the desired voltage and capacity levels. It involves connecting multiple sets of batteries in series and then in parallel.

Part 6. Safety and maintenance

Ensuring safety and proper maintenance practices are essential for prolonging battery life and preventing accidents:

Thermal Runaway

Thermal runaway is when a battery’s temperature rapidly increases due to internal reactions or external factors. It can lead to a self-sustaining, uncontrollable increase in temperature, potentially resulting in a fire or explosion. Batteries are equipped with safety mechanisms such as thermal sensors, protection circuits, and temperature management systems to prevent thermal runaway.


Overheating is when a battery operates at a temperature higher than its recommended range. High temperatures can accelerate chemical reactions within the battery, leading to reduced capacity, shorter lifespan, and increased risk of thermal runaway. Adequate cooling and proper ventilation are essential to prevent overheating and maintain battery performance and safety.

Short Circuit

A short circuit occurs when a battery’s positive and negative terminals are connected directly, bypassing the intended circuitry. This can lead to a sudden discharge of a large amount of current, potentially causing damage to the battery and surrounding components. Proper insulation, protection circuits, and handling precautions are necessary to prevent short circuits.


Some batteries, especially lithium-ion batteries, have safety features such as pressure relief valves or vents. These features allow the release of gases or built-up pressure in case of overcharging or other potentially hazardous conditions, ensuring the safety of the battery and its surroundings.

Battery Degradation

Battery degradation refers to the gradual loss of a battery’s capacity and performance over time. Factors such as usage patterns, temperature exposure, and charging/discharging cycles can contribute to degradation. Regular maintenance, proper charging practices, and avoiding extreme operating conditions can help minimize degradation and extend the battery’s lifespan.

Cell Balancing

Cell balancing is a process used in multi-cell batteries, such as lithium-ion battery packs, to ensure each cell has a balanced state of charge. Balancing prevents overcharging or over-discharging specific cells, leading to capacity imbalances and reduced overall battery performance. One can achieve balancing by actively monitoring and controlling cell voltages during charging and discharging.

State of Charge (SoC)

The state of charge refers to the remaining capacity in a battery, expressed as a percentage. Monitoring the SoC helps prevent over-discharging, which can damage the battery, and ensures the battery’s availability for use. Some batteries have built-in SoC indicators, while others require external measurements or sophisticated algorithms to estimate the SoC accurately.

State of Health (SoH)

The state of health refers to a battery’s overall condition and performance capability compared to its original specifications. It considers capacity loss, internal resistance increase, and overall degradation. Assessing the SoH helps determine the remaining lifespan and reliability of the battery, allowing for timely maintenance or replacement if necessary.

7부. 결론

Understanding battery terminology is essential for effectively utilizing and maintaining batteries in various applications. Whether using rechargeable lithium-ion batteries in your smartphone or relying on lead-acid batteries for backup power, familiarizing yourself with the terminology will help you make informed decisions, ensure optimal battery performance, and promote safety.



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