How much do you know about battery terminology?
As a leading company specializing in battery production, we understand the vital role batteries play in modern society. To deepen everyone’s understanding of batteries, we’ve compiled some professional battery terminology, aiming to be helpful to all. Let’s dive in!
Battery: A power supply device consisting of one or more electrochemical cells with external connections, used to power electrical equipment.
Battery cell: Refers to a single component containing positive and negative electrodes and other necessary electrochemical and structural components. A battery cell is an independent energy conversion device delivering electrical energy to an external circuit through a controlled internal chemical process. This conversion involves the transfer of ions between electrodes with different potentials.
Primary cell: Also known as a disposable battery, this battery can only be discharged once. Once all the chemical substances inside have reacted, it can no longer provide electrical energy or store externally supplied electricity, rendering it unusable after complete discharge.
Secondary cell: Also known as rechargeable battery, it is a battery that provides electrical energy through a reversible electrochemical process. This means that chemical energy converted into electrical energy can be recovered by applying an electric current in the opposite direction to that which flows during battery use. The current flowing in the battery during use is called discharge current, and the current that restores chemical energy is called charging current. Secondary batteries have the ability to store chemical energy when not in use. For example: lithium-ion batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc.
Battery module: An assembly of battery cells connected in series, parallel, or series-parallel configurations, featuring only one pair of positive and negative output terminals. Battery modules are the smallest repeating building blocks within a battery pack.
Battery pack: Comprising multiple battery modules connected in parallel or series, a battery pack is assembled with components such as casings, management and protection devices to meet specific application requirements.
Battery Management System (BMS): A system managing batteries intelligently, used to manage and maintain each battery unit, monitor battery status, and prevent overcharging and over-discharging to extend battery life. Common functions of BMS include power measurement, communication, state of charge (SoC) estimation, state of health (SoH) estimation, abnormal warning, abnormal protection, equalization, temperature measurement, and battery measurement, etc. For specific details, please refer to the article “What is the BMS of lifepo4 battery pack?“.
Battery model: Taking a cylindrical lithium-ion battery as an example, it is usually represented by five digits, with the first two denoting battery diameter, the next two indicating battery height, and the fifth representing cylindrical shape. For example, plb’s IFR26650 battery refers to a cylindrical battery with a diameter of 26mm and a height of 65mm.
Calendar aging: Calendar aging is the irreversible proportion of capacity loss during storage. In other words, it is degradation caused by battery storage.
C-rate: C is used to express the ratio of charge and discharge current. For instance: a battery discharged at a discharge rate of nC will provide its rated capacity in 1/n operating time. For example, for a 2500mAh battery, 1C represents 2500mA (1 times of 2500mAh). It is discharged at a rate of 1C, and it takes 1 hour to fully discharge. By analogy, discharging at a rate of 0.5C (1250mA) will take 2h to fully discharge. Specific details can be found in the article “What is a high-rate battery?“.
Cycle life: Cycle refers to the period of time from the beginning of one charge/discharge to the beginning of the next charge/discharge. Cycle life refers to the maximum number of times a battery can maintain stable performance and capacity without decreasing during charging and discharging.
Depth of Discharge (DoD): Depth of Discharge is the ratio of the amount of discharge to the total power of the battery during use. DoD=100% means the battery is out of battery, DoD=0% means the battery is fully charged. DoD terminology is usually used when describing the cycle life of the battery.
Positive electrode: The electrode with the higher potential in a primary cell or electrolytic cell. During battery discharge, it behaves as a cathode due to the reduction reaction that occurs in the electrolyte. During battery charging, it behaves as an anode due to the oxidation reaction that occurs in the electrolyte.
Negative electrode: The lower potential electrode in a primary cell or electrolytic cell. During battery discharge, it behaves as an anode due to the oxidation reaction that occurs in the electrolyte. During charging of the battery, it behaves as a cathode due to the reduction reaction that occurs in the electrolyte.
Electrolyte: Electrolyte refers to a compound that can produce ions and conduct electricity between the positive and negative electrodes of a battery in a solution or molten state.
SEI (Solid Electrolyte Interface): SEI is a passivation layer formed on the surface of the lithium ion anode material by the decomposition of electrolyte. The quality of SEI has a crucial impact on lithium-ion battery performance.
Self-discharge: Self-discharge is the loss of battery capacity caused by internal spontaneous reactions when the battery is not connected to an external circuit.
State of charge (SoC): The state of charge is also called the remaining capacity. It is used to reflect the remaining capacity of the battery. It is commonly expressed as a percentage and the value range is 0-1. When SoC=0, it means the battery is fully discharged, and when SoC=1, it means the battery is fully charged.
State of Health (SoH): SoH is defined as the ratio of a battery’s condition to its ideal condition, expressed as a percentage. Usually the SoH of a new factory battery is 100%, which decreases with time and use.
Trickle charge: Trickle charge uses a low-rate charging current to compensate for the capacity loss caused by self-discharge after the battery is fully charged, thereby maintaining a nearly fully charged state.
I believe this overview provides a better understanding of batteries. I hope these terms assist you in making informed decisions when selecting and using batteries.