• Battery Glossary
  • Date:【2012-11-13】
  • Ampere hours (Ah) - The unit of measure used for comparing the capacity or energy content of batteries with the same output voltage. For automotive (Lead Acid) batteries the SAE defines the Amphour capacity as the current delivered for a period of 20 hours until the cell voltage drops to 1.75 V.

    Strictly - One Ampere hour is the charge transferred by one amp flowing for one hour. 1Ah = 3600 Coulombs.

    Battery Management System (BMS) - Electronic circuits designed to monitor the battery and keep it within its specified operating conditions and to protect it from abuse during both charging and discharging.

    Battery Monitoring - Sometimes confused with BMS (above) of which it is an essential part, these circuits monitor the key operating parameters (current, voltage, temperature, SOC, etc.) of the battery and provide information to the user.

    Bobbin - A cylindrical cell design utilizing an internal cylindrical electrode and an external electrode arranged as a sleeve inside the cell container.

    C Rate - C is a value which expresses the rated current capacity of a cell or battery. A cell discharging at the C rate will deliver its nominal rated capacity for 1 hour. Charging and discharging currents are generally expressed as multiples of C. The time to discharge a battery is inversely proportional to the discharge rate.

    NC is a charge or discharge rate which is N times the rated current capacity of the battery where N is a number (fraction or multiple)

    CN is the battery capacity in AmpHours which corresponds to complete discharge of the battery in N hours (N is usually a subscript). Also written as the N-Hour rate.

    Capacity - The electric energy content of a battery expressed in "Watt hours". Batteries with the same output voltage also use "Ampere hours" for comparing capacities.

    Cathode - The electrode in an electrochemical cell where reduction takes place, gaining electrons. During discharge the positive electrode of the cell is the cathode. During charge the situation reverses and the negative electrode of the cell is the cathode.

    Cell balancing - The process used during charging to ensure that every cell is charged to the same state of charge. Also called "Equalisation".

    Charge - The process of replenishing or replacing the electrical charge in a rechargeable cell or battery.

    Charge efficiency - The ratio (expressed as a percentage) between the energy removed from a battery during discharge compared with the energy used during charging to restore the original capacity. Also called the Coulombic Efficiency or Charge Acceptance. See alternative definition above.

    Constant current charge CC - A charging scheme which maintains the current through the cell at a constant value.

    Constant voltage charge CV - A charging scheme which maintains the voltage across the battery terminals at a constant value.

    Current limit - The maximum current drain under which the particular battery will perform adequately under a continuous drain.

    Cut-off voltage - The specified voltage at which the discharge of a cell is considered complete.

    Cycle life - The number of cycles a battery can perform before its nominal capacity falls below 80% of its initial rated capacity.

    Deep cycle battery - A battery designed to be discharged to below 80% Depth of Discharge. Used in marine, traction and EV applications.

    Depth of discharge DOD - The ratio of the quantity of electricity or charge removed from a cell on discharge to its rated capacity.

    Discharge capacity - The amount of energy taken from the battery when discharged at the rated current and ambient temperature until the discharge end voltage is reached. Generally expressed in units of Watt hours (or Ampere hours for batteries with the same voltage).

    Discharge rate - The current delivered by the cell during discharging. Expressed in Amperes or multiples of the C rate.

    Discharge voltage - The voltage between the terminals of a cell or battery under load, during discharge.

    Electrolyte - A substance which dissociates into ions (charged particles) when in aqueous solution or molten form and is thus able to conduct electricity. It is the medium which transports the ions carrying the charge between the electrodes during the electrochemical reaction in a battery.

    Energy density - The amount of energy stored in a battery. It is expressed as the amount of energy stored per unit volume or per unit weight (Wh/L or Wh/kg).

    Fast charge - Charging in less than one hour at about 1.0C rate. Needs special charger.

    Float charge - An arrangement in which the battery and the load are permanently connected in parallel across the DC charging source, so that the battery will supply power to the load if the charger fails. Compensates for the self-discharge of the battery.

    High rate discharge - Discharge at a current of 2C or more.

    IEC - The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes international standards for all electrical, electronic and related technologies.

    Intelligent battery - Battery containing circuitry enabling some communication between the battery and the application or with the charger.

    Internal impedance - Resistance to the flow of AC current within a cell. It takes into account the capacitive effect of the plates forming the electrodes.

    Internal resistance - Resistance to the flow of DC electric current within a cell, causing a voltage drop across the cell in closed circuit proportional to the current drain from the cell. A very low internal impedance is usually required for a high rate (high power) cell.

    Lithium Ion Cell - A secondary lithium cell in which both the negative and positive electrodes are lithium insertion (intercalation) compounds. Also known as rocking chair, shuttlecock or swing cell.

    Lithium Polymer Cell - A lithium ion cell with a solid polymer electrolyte.

    Memory effect - Reversible, progressive capacity loss in nickel based batteries found in NiCad and to a lesser extent in Ni-MH batteries. It is caused by a change in crystalline formation from the desirable small size to a large size which occurs when the cell is recharged before it is fully discharged.

    MSDS - Material Safety Data Sheet. Information provided by battery or cell manufacturers about any hazardous materials used in their products.

    Nominal capacity - Used to indicate the average capacity of a battery. It is the average capacity when batteries are discharged at 0.2C within one hour of being charged for 16 hours at 0.1C and 20± 5°C. (or discharge at 0.05C for automotive batteries - SAE) Definition depends on the conditions. See Ampere Hours Ah above

    Nominal voltage - Used to indicate the voltage of a battery. Since most discharge curves are neither linear nor flat, a typical value is generally taken which is close to the voltage during actual use.

    NTC - A thermistor with a negative temperature coefficient, whose resistance decreases with increasing temperature.

    Open circuit voltage OCV - The voltage of a cell or battery with no load attached measured with a voltmeter at room temperature.

    Operating voltage - Voltage between the two terminals of the battery with a load connected.

    Over-charge - Continuous charging of the battery after it reaches full charge. Generally overcharging will have a harmful influence on the performance of the battery which could lead to unsafe conditions. It should therefore be avoided.

    Over-current - Exceeding the manufacturer's recommended maximum discharge current for a cell or battery.

    Over-discharge - Discharging a battery below the end voltage or cut-off voltage specified for the battery.

    Parallel connection - The connection together of, two or more, similar cells to form a battery of higher capacity by connecting together all the cell terminals of the same polarity.

    Passivation layer - A resistive layer that forms on the electrodes in some cells after prolonged storage impeding the chemical reaction. This barrier must be removed to enable proper operation of the cell. Applying charge/discharge cycles often helps in preparing the battery for use. In other applications, passivation is used as a method of shielding a metal surface from attack.

    Photovoltaic cell - A device that directly converts the energy in light into electrical energy. Also called a photocell, a solar cell or a PV cell.

    Positive electrode - The electrode which has a positive potential. The cathode. Electric current from this electrode flows into the external circuit.

    PTC - A thermistor with a positive temperature coefficient, whose resistance increases with temperature.

    Quick charge - Charging in three to six hours at about 0.3C rate. Needs special charger.

    Secondary battery - A battery which can be recharged and used repeatedly.

    Self-discharge - Capacity loss during storage due to the internal current leakage between the positive and negative plates.

    Series connection - The connection of, two or more, similar cells in a chain to form a battery of higher voltage by connecting the positive terminal of each cell to the negative terminal of the next cell.

    Smart Battery - An intelligent battery which contains information about its specification, its status and its usage profile which can be read by its charger or the application in which it is used.

    Solar cell - A photovoltaic cell. Solar cells convert sunlight energy into electric current. They do not store energy.

    Spiral Wound - Battery construction in which the electrodes with the electrolyte and separator between them are rolled into a spiral like a jelly roll (Swiss roll).

    State of Charge- SOC - The available capacity of a battery expressed as a percentage of its rated capacity.

    State of Health- SOH - A measurement that reflects the general condition of a battery and its ability to deliver the specified performance compared with a fresh battery. It takes into account such factors as charge acceptance, internal resistance, voltage and self-discharge. It is not as precise as the SOC determination.

    Storage life - The length of time a cell or battery can be stored on open circuit without permanent deterioration of its performance.

    Traction battery - A high power deep cycle secondary battery designed to power electric vehicles or heavy mobile equipment.

    Trickle charge - A continuous charge at low rate, balancing losses through local action and/or periodic discharge, to maintain a cell or battery in a fully charged condition. Normally at a C/20 to C/30 rate.

    UL - Underwriters Laboratories Inc - (UL) is an independent, not-for-profit product safety testing and certification organization based in the USA. UL marking indicates that the product conforms with the safety standards laid down by Underwriters Laboratories.

    UPS - Uninterruptible Power Supply.

    Volumetric Energy Density (Wh/L) - The energy output per unit volume of a battery.

    Volumetric Power Density (W/L) -The power output per unit volume of a battery.

    Watt - A unit of power, the rate of doing work. Watts = Amps X Volts = One Joule per second.

    Watt Hours Wh - A measure of the energy capacity of a battery. The amount of work done in one hour. 1 Wh = 3.6 kJ.

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