How Does a Battery Work?

How Does a Battery Work?

Batteries are indispensable in almost all areas of our lives. From mobile phones to e-bikes (e-bike batteries), batteries power nearly all our modern devices. Therefore, we need to understand how batteries work. In this article, we will explore how batteries function and the differences between various types of batteries.

What is a battery?

A battery is a device that converts chemical energy into electrical energy. When the battery is connected to a circuit, a chemical reaction between the anode and cathode causes electrons to flow through the external circuit, generating an electric current.

This current can power a variety of devices such as mobile phones, laptops, and many other portable electronic devices. There are various types of batteries, including disposable and rechargeable batteries, and they differ in size, capacity, voltage, and performance to meet different uses and needs. As a battery manufacturer, BatteryInt sells kinds of high-quality batteries that meet different needs.


Key Parameters of Battery that You Have to Know

The voltage, current, power, and capacity are the four fundamental parameters for evaluating a battery's performance. The differences between them are as follows:


The voltage of a battery is the potential difference between its two terminals. It determines the battery's ability to drive the charge flow, essentially the "force" of the battery. Batteries are typically designed for a specific voltage, such as 1.5 volts for AA batteries or 3.7 volts for lithium-ion batteries.


Current is the amount of charge flowing through a circuit per unit of time, measured in amperes (A). The amount of current that flows when discharging a battery depends on the demands of the external circuit and the battery's maximum discharge rate.


The power of a battery is the amount of energy it can deliver or consume per unit of time, expressed in watts (W). The power of a battery can be calculated by multiplying the voltage and current (P = V × I). This is the maximum amount of energy the battery can provide at a given moment.


The capacity of a battery is the total amount of charge it can store, usually expressed in ampere-hours (Ah) or milliampere-hours (mAh). This value indicates how long a battery can provide current at full charge. For example, a 1000 mAh battery can operate for 1 hour if it delivers 1 ampere of current.

Energy Density

Another common term is energy density. Energy density describes the amount of energy stored in a battery per unit of mass (gravimetric energy density in watt-hours/kg, Wh/kg) or per unit of volume (volumetric energy density in watt-hours/liter, Wh/L). The higher the energy density, the better, as it allows the battery to be smaller and more compact, reducing the device's weight.

How Does a Battery Generate Voltage?

A battery generates voltage through electrochemical reactions that occur between the anode, cathode, and electrolyte: These components have different chemical potentials, meaning the anode tends to give up electrons while the cathode is ready to accept electrons. This imbalance leads to an excess of electrons at the anode compared to the cathode, creating a voltage or electromotive force (EMF).

Different combinations of materials and chemical reactions in batteries result in varying voltages, leading to a variety of battery types and performances. However, since the voltage of a single cell is relatively low, most large batteries (e.g., 18650 battery pack and 21700 battery pack) consist of multiple cells connected in series to increase the voltage. For example, most 12-volt batteries are made up of four to six cells connected in series.

Battery Voltage Test

Why does a battery have a Negative and a Positive Electrode?

Batteries have a negative and a positive electrode to create a potential difference that drives the flow of electrons and generates an electric current. As electrons move from one pole to the other, they produce an electric current in the devices along their path, providing energy.

This electron flow from the negative pole to the positive pole occurs because the positive pole has a higher potential compared to the negative pole, and electrons always flow from a lower potential to a higher potential. Therefore, the negative and positive poles are fundamental to the structure of the battery and crucial for its efficient function. This design allows the battery to serve as a reliable power source in various devices

How does Current Flow in a Battery?

In a battery, the flow of current is achieved through the movement of electrons and ions. When a battery is connected to a device, the negative electrode (anode) releases electrons through a chemical reaction. These electrons flow through an external circuit to the positive electrode (cathode), generating an electric current.

Simultaneously, ions in the electrolyte within the battery move from one electrode to the other to maintain charge balance. This flow of electrons and movement of ions together drive the current in the battery, allowing it to power a variety of electronic devices

What is the Difference Between Non-Rechargeable and Rechargeable Batteries?

The difference between non-rechargeable (primary) and rechargeable (secondary) batteries lies in their ability to be recharged and reused:

Non-rechargeable batteries (Primary batteries)

These batteries are designed for one-time use. Once their stored chemical energy is converted into electrical energy and used up, they cannot be recharged. They are typically cheaper to purchase and are used in devices that require little power or are used infrequently. Examples include alkaline batteries used in clocks, remote controls, and flashlights.

Rechargeable batteries (Secondary batteries)

These batteries can be recharged after being discharged. They contain special chemical substances that allow the discharge reactions to be reversed when connected to a power source. Although they are more expensive to purchase, they are more economical in the long run since they can be recharged hundreds of times. They are commonly used in devices that need higher power supply or are frequently used, such as smartphones, laptops, and electric vehicles.

The main difference lies in the usage duration and reusability. While non-rechargeable batteries must be disposed of after use, rechargeable batteries offer the ability to regain full performance through recharging, making them both more environmentally friendly and cost-efficient.

4 Batteries are charging

Does a Battery Lose its Charge When not in Use?

Yes, a battery slowly loses its charge even when not in use. This process is known as self-discharge. The rate of self-discharge depends on various factors, including:
Battery type
Different types of batteries have different self-discharge rates. For example, nickel-metal hydride (NiMH) batteries have a higher self-discharge rate compared to lithium-ion batteries.
Higher temperatures can accelerate the self-discharge rate of batteries. Therefore, it is advisable to store batteries in cool and dry conditions to preserve their charge longer.
Age and condition of the battery
Older batteries or those that are damaged in some way can lose their charge more quickly.
This self-discharge is one of the reasons why even unused batteries need to be recharged or replaced after a certain period.

How to Measure a Battery?

To measure a battery and assess its condition, various parameters can be used. Here are the measurement methods:
Measuring Voltage
The simplest way to check a battery's condition is to measure the voltage with a multimeter. A fully charged battery should measure close to its rated voltage, while a significantly lower measurement indicates that the battery may be discharged or defective.
Testing Capacity
The capacity of a battery indicates how much energy it can store, measured in ampere-hours (Ah). Capacity tests are conducted by discharging the battery under controlled conditions and measuring the actual amount of current delivered. Specialized battery testers or charge/discharge devices can be used for this purpose.
Measuring Internal Resistance
An increase in internal resistance can indicate that the battery is aging or damaged. Internal resistance can be measured with specialized instruments, such as an internal resistance meter. This device sends a small current through the battery and measures the resulting voltage drop. Generally, the lower the internal resistance of a battery, the better its performance.
Conducting Load Tests
Load tests are useful for evaluating battery performance under real-world conditions. By using a load tester to apply a realistic load to the battery and measuring its response, you can assess its performance. This type of test simulates the battery's behavior under actual usage conditions and checks its stability and performance under varying loads.
These measurement methods help not only in assessing the current condition of a battery but also in predicting how much lifespan is left and when a battery should be replaced.



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