This glossary of technical terms is designed to help you understand terms commonly used in the battery industry.
Active substance
An electrochemical substance is used to produce positive and negative electrodes.
Absorbed Glass Mat (AGM)
An AGM is a type of lead-acid battery that contains a glass mat to facilitate the recombination of gases produced during the charging process.
Ambient Temperature
The temperature of the surrounding surface on which the battery is located.
Ampere
A unit of measurement for current.
Ampere-hour
The result of multiplying current (amps) by time (hours). It is used to express the capacity of a battery and is referred to as ampere hours or A.H.
Anode.
The electrode releases electrons when discharged. When powering equipment, the anode is positive and negative when discharging.
Battery
A combination of two or more batteries connected in series or parallel. See Series/Parallel Connection Guide.
BESS
Battery Energy Storage System, also known as ESS.
BMS
A battery management system used internally or externally to manage charging and discharging and provide SoC (State of Charge) and SoH (State of Health) data. It is essential for protecting the battery and extending its life.
Bluetooth
Low-power radio communication with a transmission distance of up to 10 meters (30 feet). With Bluetooth and the Battery Management System (BMS), Keheng Lithium Bluetooth batteries provide instant access to battery status through smart devices.
Indicates that the charge or discharge rate equals the battery capacity divided by one hour. For example, a 2000 mAh battery has a C value of 2.0 amps. The same battery has a C/5 value of 400 mA and a C/10 value of 200 mA. See more detailed information on what constitutes a battery’s C-value.
Capacity
The amount of electrical energy, in ampere-hours, that a battery or battery pack can provide.
- Available Capacity: The number of ampere-hours a battery can be discharged based on its state of charge, discharge rate, ambient temperature, and specified cutoff voltage.
- Rated Capacity (“C”): Thcutoffharge capacity claimed by the manufacturer to be achievable at a given discharge rate and temperature.
- Capacity Decline: A reduction in capacity due to undercharging.
- Capacity Offset: Capacity adjustment when a battery is discharged higher than the specified C rate.
Cathode
The electrode in a battery undergoes a reduction reaction by absorbing electrons. When discharging, the cathode is positive; when charging, the cathode becomes negative.
Cell
The basic unit of a battery. Lead-acid batteries have a nominal voltage of 2 volts, while lithium-iron phosphate batteries have a nominal voltage of 3.2 volts.
- Secondary Battery: A reversible process that allows for repeated charging and discharging.
- Battery Polarity Reversal: Occurs when a battery reverses polarity due to over-discharge.
- Battery Mismatch: Batteries in a battery pack that does not have the same capacity, voltage, or internal resistance values.
- Primary Battery: A battery or battery pack that can only be discharged once and cannot be recharged. Examples include alkaline manganese-zinc batteries.
- Secondary Battery: A reversible process in which charging and discharging can be repeated—for example, lead-acid batteries.
- Cylindrical Battery: Positive and negative plates rolled into a cylindrical shape and placed in a cylindrical container. Examples include AA and 18650 batteries.
- Prismatic batteries: batteries in which the positive and negative plates are not rolled but stacked.
- Pouch Battery: Packaged in a heat-sealable, flexible aluminum foil pouch.
- Power Cells: Designed to deliver maximum current and high discharge rates.
- Energy batteries: Designed for maximum capacity and longer cycle life.
Charging
The conversion of electrical energy into chemical energy is restoring electrical energy to a battery or accumulator. Provides guidelines for charging lead-acid and lithium batteries.
- Charge Retention: The ability of a battery to hold a charge, which diminishes during storage.
- Charge Acceptance: A measure of the charge accumulated in a battery.
Oat Charge: This method maintains the capacity of a battery or battery cell by applying a constant voltage.
Trickle Charge: This method maintains the capacity of a battery or battery pack by applying a small current.
Equalization Charging: This process ensures that all cells in a battery or battery pack reach the same state of charge.
CLOSED CIRCUIT VOLTAGE TEST: A test method in which the voltage is monitored while the battery is briefly discharged at a constant current.
Coulomb: A unit of charge defined as 1 ampere second (1C = 1 As).
Cut-off Voltage: The final voltage reaches the cutoff battery or cell after charging or discharging.
Cycle: A single charge or discharge of a battery or cell.
Cycle Life: The total number of charge and discharge cycles a battery can undergo before it reaches the end of its useful life.
Deep Cycle: The cycle in which a battery is discharged to its cut-off voltage, lead-acid batteries arecutoffy discharged to about 80%.\
Direct Current (DC): The type of current supplied by a battery where one end is always positive and the other negative.
Discharge: The act of drawing current from a battery.
Deep Discharge (DoD ): occurs when a battery or cell is discharged to 80% to 100% of its rated capacity.
Depth of Discharge (DoD ): The percentage of capacity consumed during discharge.
Self-discharge is when a battery’s capacity decreases when it is not in use or stored.
Self-Discharge Rate (SDR): The rate at which a battery loses capacity due to an open circuit in a given period.
Discharge: The act of drawing current from a battery.
Parasitic Discharge: The phenomenon in which a battery continues to discharge when the vehicle engine is turned off.
Electrodes: Positive or negative plates that contain materials capable of reacting with an electrolyte to produce or receive an electric current.
Electrolyte: A substance that conducts ions within a battery; for lead-acid batteries, this is usually a sulfuric acid solution.
End-of-Charge Voltage: The voltage of a cell or battery while it is still connected to the charger at the end of a charge.
Energy Density: The ratio of a battery’s energy to its volume or weight, usually measured in watt-hours/cubic inch/mm or pounds/kg.
Gas Recombination: Oxygen produced by the positive plates is absorbed by the negative plates during the final charging stage, thus preventing water loss.
High Rate Discharge: The rapid discharge of a battery, usually expressed as a multiple of C (the ampere rating of the battery).
Specific Gravity Meter: A device used to measure the density of a liquid to indicate the state of charge of a lead-acid battery.
Impedance: The resistance of a battery to alternating current (AC), measured in ohms (Ω), usually at 1000 Hz when the battery is fully charged.
Internal Resistance: The resistance within a battery causes a voltage drop associated with the current drawn.
Lithium-ion Battery: A rechargeable battery that uses cobalt, manganese, iron, and/or other metals as the cathode and graphite as the anode.
Negative electrode: The terminal where electrons flow from the external circuit when the battery is discharged.
Nominal capacity: the standard value of the rated capacity of the battery.
Nominal Voltage: The standard value of the rated voltage of the battery.
Open Circuit Voltage: The voltage of a battery or cell measured without a load.
Overcharging: Batteries are continually charged beyond 100% capacity, which can shorten battery life if continued for too long.
Parallel Connection: A configuration in which multiple batteries or battery cells are connected by connecting all terminals of the same polarity, increasing the total capacity of the battery pack.
Polarity: The charge distribution of the battery terminals.
Positive: Terminal where electrons flow through an external circuit when the battery is discharged.
Rated Capacity: The capacity of a battery, measured in amperes, after a specified number of hours at a constant current at a specified depth of discharge and room temperature.
Recombination: The state of recombination of gases usually produced by a battery during operation.
Series connection
This is the process of increasing the total voltage of a battery pack by connecting a group of cells or batteries with opposite polarity terminals.
Self-discharge
This refers to a battery’s capacity loss when it is stored or left idle, even in the absence of an external load.
Separator
A material that separates the positive and negative plates of a battery. This material is usually made of absorbent glass fibers in sealed lead-acid batteries that help keep the electrolyte in suspension.
Sealed Lead Acid Battery
Sealed lead-acid batteries (SLA) are characterized by being maintenance-free and leak-proof. These batteries are equipped with safety venting valves that release gas in the event of excessive internal pressure and are also known as valve-regulated lead-acid (VRLA) batteries.
Gel Battery
Gel batteries are a type of SLA battery in which the dilute sulfuric acid electrolyte is converted to a gel by an additive that prevents it from flowing freely.
Service Life
This term indicates the expected service life of a battery, measured in terms of its total number of cycles or years of standby service while still retaining a specified percentage of its original capacity.
Shelf Life
The maximum time a battery can be stored without recharging.
Standby Service
An application scenario in which trickle or float charging methods keep a battery in a fully charged state.
State of Charge (SoC)
The current capacity of a battery is a percentage of its rated capacity at a given moment in time.
Absolute State of Charge (ASoC)
Indicates the ability of a battery to receive a specified charge when it is first produced.
State of Health (SoH)
This indicator is used to evaluate battery performance, verifying parameters such as capacity, current output, voltage, and self-discharge, and is expressed as a percentage.
Sulfation
The process by which lead sulfate is formed or deposited on the surface and in the pores of the active material of a battery’s lead plates. Excessive sulfation can lead to oversized crystals on the plates, resulting in inefficient operation or complete failure of the battery.
Thermal runaway
A condition in which a cell or battery pack self-destructs due to internal heat generation, especially under continuous charging.
Valve Regulated Lead Acid (VRLA) Battery
See the definition of SLA battery.
Watt
A unit of power derived by multiplying amperes (A) and volts (V), i.e., watts (W).
Watt-hour
This unit expresses electrical energy equivalent to one watt of power consumed in one hour. The watt-hour (Wh) energy of a battery can be determined by multiplying its voltage (V) by its rated capacity (Ah).