Batteries, accumulators, chargers - terminology glossary

battery

An electrochemical device capable of converting electrical energy into chemical energy (charging), and - by reversing the process - to release electrical energy stored in the form of chemical energy (discharging). It consists of one or more (battery) electrochemical cells.

Amper [A]

The unit of measurement for electric current intensity.

ampere-hours [Ah]

The product of current intensity (measured in amperes) by the length of time (in hours) for which the battery can deliver current at that intensity. Battery capacity is usually given in ampere-hours - according to the definition, a battery with a capacity of 1Ah can deliver a current of 1A for one hour, a current of 0.5A for two hours, etc.

anode

The positive electrode on which oxidation occurs in a liquid solution - anions (negative ions) are released. In the case of rechargeable batteries, depending on the direction of current flow (charging or discharging), either of the two electrodes can function as the anode. The negative electrode is the anode during discharging.

battery

In common language, it refers to one or more galvanic (electrochemical) cells connected electrically (in series, parallel), allowing the connection of other electrical devices to them.

alkaline battery

A battery in which an alkaline solution is used as the electrolyte. The most popular electrolyte of this type is potassium hydroxide. Batteries of this type do not contain mercury or cadmium.

primary battery

A battery that can be used only once. It cannot be subjected to a charging process to reverse the chemical reactions that produced current from it. Examples of primary batteries include zinc-carbon and alkaline batteries. The opposite of a primary battery is a rechargeable battery (secondary battery), in which the chemical processes occurring during discharging (usage) are reversible.

secondary battery

see accumulator

CC/CV

CC - constant current, CV - constant voltage - terms defining the basic phases of charging lithium-based batteries. For a typical Li-ion 3.7V battery, charging begins with the constant current CC phase. The battery is charged with a constant current until the final voltage is reached - usually 4.20V. After reaching the final voltage, the current begins to decrease and the charging process enters the CV phase - constant voltage charging. Charging ends after the current drops to a specified (usually 50-150 mA) value. The current at which charging ends is called the termination current.

external factors

Factors that can affect the efficiency and lifespan of batteries - such as temperature, humidity, vibrations, shocks, etc.

cycle

In batteries, a single sequence of charging and discharging (usage) processes of the battery.

storage time

The time for which an unused battery can be stored without irreversible loss of its properties. The length of this time depends on how quickly self-discharge processes occur in the battery.

memory effect

A controversial phenomenon that supposedly occurs in some types of batteries (e.g., nickel-cadmium). It is said to involve a reduction in battery capacity when its work cycle is completed with incomplete discharging.

positive electrode

The electrode that accepts electrons during the discharging (usage) process of the battery.

negative electrode

The electrode that supplies electrons during the discharging (usage) process of the battery.

energy

Along with capacity, this is a value that determines the efficiency of the battery/accumulator. To measure it, it is necessary to draw all the stored energy from a fully charged battery/accumulator (the discharging process must be carried out). The energy stored in the battery is usually measured in watt-hours [Wh]. A battery with an energy of 1Wh can deliver a power of 1W for one hour, a power of 0.5W for two hours, etc. The value of stored energy [Wh] in relation to capacity [Ah] is more complementary and useful for assessing the performance of a given battery, as it takes into account the voltage value throughout the entire discharge process.

electrolyte

A substance that allows the movement of ions within the electrochemical cell. Energy density is a characteristic value for a given electrochemical system, measured in [Wh/m3]. It defines the amount of energy that a battery can store per unit volume.

cathode

The negative electrode on which reduction processes occur, i.e., cations (positively charged ions) accept electrons (negative charges). In batteries, either electrode can function as a cathode, depending on the direction of current. The positive electrode is the cathode during normal battery operation (discharging).

charging

The process during which externally supplied electrical energy is converted into chemical energy stored in the battery.

trickle charging

The process to which most chargers subject batteries after completing their charging to full capacity, counteracting the natural tendency of the battery to self-discharge. In the case of popular rechargeable batteries (Ni-Cd, Ni-MH), this is charging with a very small current.

charger

A device that supplies electrical energy to batteries during the charging process.

milliwatt-hours [mWh], watt-hours [Wh]

Units defining the electrical energy that a given battery or accumulator can accumulate. Unlike the capacity unit expressed in milliampere-hours/ampere-hours, the energy value takes into account the output voltage of the given battery, allowing energy values to be compared between each power source.

voltage

Measured in volts [V], the difference in potential between the electrodes of the battery. In the case of cells, it depends on the electrochemical system of the cell. In the case of batteries consisting of several cells, it also depends on the type of electrical connections between the individual cells (series, parallel).

final voltage

The voltage at which the discharging or charging process of the battery or accumulator is completed. In the case of lithium batteries, it refers to the final voltage to which the cell is charged in the CV phase. After reaching and stabilizing this voltage, the charger should stop charging.

termination voltage

See final voltage.

electrochemical cell

The smallest unit that makes up a battery - it consists of a positive and negative electrode, a separator, and an electrolyte. It stores electrical energy in chemical form. The capacity of the cell depends on its size, while the voltage of the cell depends on the electrochemical type of the cell. All cells are capable of converting chemical energy into electrical energy, some (batteries) can also convert the electrical energy supplied to them into chemical energy (charging).

capacity (C)

A value that determines the efficiency of the battery/accumulator. The only method of determining capacity is to draw all the stored capacity from a fully charged battery/accumulator (the discharging process must be carried out). The capacity of the battery is usually measured in ampere-hours [Ah]. A battery with a capacity of 1Ah can deliver a current of 1A for one hour, a current of 0.5A for two hours, etc. The charging/discharging current for batteries is often expressed in multiples of C - e.g., a current of 0.1C for a battery with a capacity of 1.4Ah (1400mAh) is 140mA.

termination charging current

A term characteristic for lithium-based batteries. It defines the minimum charging current with which the lithium cell is charged after reaching the final voltage in the constant voltage (CV) charging phase.

internal resistance

In batteries and accumulators, it defines the inherent resistance of the cell. Each battery and accumulator operates within a certain range like a standard resistor, where the current flowing through it causes a voltage drop. The greater the resistance the battery presents, the greater the voltage drop it causes, and consequently, less current can flow through it to the target device. A battery with higher resistance generates a higher voltage drop at the terminals during discharging - according to Ohm's basic law. The increase in internal resistance is a natural phenomenon of battery and accumulator operation as they age. This is a very negative phenomenon, as it often leads to premature and unexpected shutdown of the device in use. Energy losses associated with the internal resistance of the battery are dissipated as heat directly on the battery and its contacts. High internal resistance can lead to overheating of batteries and accumulators in demanding devices - e.g., flashlights. Along with capacity, this is one of the most important and significant parameters determining the performance of a battery or accumulator, of which not everyone is aware. There are only a few proven chargers on the market that can correctly measure and provide the user with the resistance value - such chargers include everActive NC-3000 for Ni-MH batteries and everActive LC-2100 for lithium-ion batteries.

self-discharge

Self-discharge - this is a phenomenon occurring in batteries as a result of chemical reactions occurring within them without connection between the battery terminals. Self-discharge reduces the lifespan of the battery and causes it to have a lower charging capacity than that which was assumed when starting to use the cell.
How quickly and how violently the self-discharge process occurs depends on the type of battery and factors such as operating and storage temperature.
Typically, lithium batteries have a lower self-discharge capacity (about 2-3% of total capacity per month), while nickel-based batteries are more prone to self-discharge (nickel-cadmium Ni-Cd 15-20% of total capacity per month, while nickel-metal hydride Ni-MH 30% of total capacity per month). In the case of cells made with Ni-MH technology, the exception is new generation batteries - e.g., Eneloop, which can maintain useful capacity for many years.
As can be seen, this process has a very large impact on the operational performance of the battery.
Assuming what we know, namely the fact that self-discharge is a chemical reaction, we can ask the question, what exactly factors influence the occurring process?
Self-discharge is a chemical process occurring in a closed loop and usually occurs faster at higher temperatures. Storing batteries at lower temperatures reduces the rate of self-discharge and helps retain the initial energy stored in the battery.
More specific causes of the phenomenon have not yet been precisely understood.

separator

An electrical insulator that separates the electrodes within the electrochemical cell.

electrochemical system

The structure and chemical components that make up the cell, determining its parameters.

lifespan

Defines the durability of the battery - usually given in work cycles. Generally, lifespan largely depends on the operating conditions of the battery. Copyright © Baltrade