AC Inverter - An electrical circuit which generates a sine-wave output (regulated and without breaks) using the DC current supplied by the rectifier-charger or the battery. The primary elements of the inverter are the DC/AC converter, a regulation system and an output filter.
Acid - A proton donor. A compound containing hydrogen which dissociates in aqueous solution producing positively charged hydrogen ions (H+). An acidic solution has a pH less than 7.0
Alkaline battery - A battery which uses an aqueous alkaline solution for its electrolyte.
Ambient temperature - The average temperature surrounding the battery, typically
Ampere (Amp) - The unit of current flow equal to one coulomb per second.
Ampere hours (Ah) - The unit of measure used for comparing the capacity or energy content of a 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.
Battery - Two or more electrochemical energy cells connected together to provide electrical energy.
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 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.
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.
CCA – Cold Cranking Amperes - A measure used to specify the cold cranking capability of automotive SLI batteries. For Lead Acid batteries it is the constant current a battery can deliver during a continuous discharge over a period of 30 seconds at -18°C without the terminal voltage dropping below a minimum of 1.2 Volts/cell.
Cell - A closed electrochemical power source. The minimum unit of a battery.
Cell chemistry - The active materials used in the energy cell.
Cell reversal - A condition which may occur multi cell series chains in which an over discharge of the battery can cause one or more cells to become completely discharged. The subsequent volt drop across the discharged cell effectively reverses its normal polarity.
Charge - The process of replenishing or replacing the electrical charge in a rechargeable cell or battery.
Charge rate - The current at which a cell or battery is charged. Generally expressed as a function of rated capacity C.
Conductance - Strictly speaking the Conductance applies to resistive circuits and is the reciprocal of the Resistance. Battery manufacturers have their own definition which applies to the frequency dependent elements of the circuit, that is – C=I/E where C is the conductance, I is the test current applied to a component (the cell) and E is the in phase component of the ac voltage E producing it.(Compare with Ohm’s Law R=E/I) Measuring the conductance of a battery gives a good indication of its state of health.
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. See also End voltage and Termination voltage
Cycle - A single charge and discharge of a battery.
Cycle life - The number of cycles a battery can perform before its nominal capacity falls below 80% of its initial rated capacity. See also Float life below.
DC-DC Converter - An electronic circuit which takes a DC input voltage and converts it to a different, desired DC output voltage.
Deep cycle battery - A battery designed to be discharged to below 80% Depth of Discharge. Used in marine, traction and EV applications.
Deep discharge - Discharge of at least 80% of the rated capacity of a battery.
Discharge - The change from chemical energy within the cell into electrical energy to operate a external circuit.
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.
Dry Cell - A Leclanché cell with a gel electrolyte.
Duty Cycle - The load current or power a battery is expected to supply for specified time periods.
Electrolysis - Chemical modifications, oxidation and reduction produced by passing an electric current through an electrolyte.
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.
End voltage - The prescribed voltage that indicates that the discharge is complete. (see also Cut-off voltage)
Energy Content - The absolute amount of energy stored in a battery expressed in Wh or Joules
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.
Float life - The expected lifetime in hours of a battery when used in a float charge application. See also Cycle life above.
Flooded Lead Acid cell - In “flooded” batteries, the oxygen created at the positive electrode is released from the cell and vented into the atmosphere. Similarly, the hydrogen created at the negative electrode is also vented into the atmosphere. This can cause an explosive atmosphere in an unventilated battery room. Furthermore the venting of the gasses causes a net loss of water from the cell. This lost water needs to be periodically replaced. Flooded batteries must be vented to prevent excess pressure from the build up of these gasses. See also Sealed Lead Acid (SLA) Cells which overcome these problems.
Flywheel battery - A flywheel stores kinetic energy in a high speed (up to 100,000 rpm) rotating cylinder and is “charged” and “discharged” via an integral motor/generator. High power availability but low capacity.
Gassing - The generation of a gaseous product at one or both electrodes as a result of the electrochemical action. In Lead Acid batteries gassing produces hydrogen and oxygen.
Gel cell - A battery which uses gelled electrolyte, an aqueous electrolyte that has been fixed by the addition of a gelling agent.
Hertz - The standard unit of frequency of one cycle per second.
Hibernation state - A state in which the the status of the various functions of a circuit has been saved in memory and the circuit has been switched off save energy. When power is reapplied, data taken from the memory is used to restore the circuit to the status it had before switch off. (See also “Standby state” below)
High rate discharge - Discharge at a current of 2C or more.
Horse Power (Hp) - The rate of doing work. 1 Hp = 746 Watts or 550 foot pounds per second.
Hydrometer - A device used for measuring the specific gravity of a fluid. In the case of lead acid batteries the specific gravity provides a measure of the state of charge of the cell.
Hygrometer - An instrument for measuring humidity. Often confused with a hydrometer.
IEC - The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes international standards for all electrical, electronic and related technologies.
Immobilised electrolyte - A construction technique used in lead-acid batteries. The electrolyte (the acid) is held in place against the plates instead of being a free-flowing liquid. The two most common techniques are Gel Cell and Absorbed Glass Mat.
Impedance - A measure of the response of an electric circuit to an electric current. The actual value is frequency dependent. The current is opposed by the capacitance, inductance and resistance of the circuit.
Impedance testing - Determination of the battery’s internal impedance by measuring the voltage drop across a cell when it carries a sample alternating current.
Inductance (L) - A measure of the ability of a device to store magnetic flux per unit of rate of change of current passing through the device. Measured in Henries. The voltage across the inductor is given by the relationship v = -L d/dtI(t)
Intelligent battery - Battery containing circuitry enabling some communication between the battery and the application or with the charger.
Intelligent charger - Charger which is able to react to inputs from an intelligent battery to control or optimize the charging process.
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 low internal impedance is usually required for a high rate cell.
Inverter - An electrical circuit which generates a sine-wave output (regulated and without breaks) using the DC current supplied by the rectifier-charger or the battery. The primary elements of the inverter are the DC/AC converter, a regulation system and an output filter.
Ion - An atom or group of atoms which is electrically charged. Depending on how they were created – through release or absorption of electrons – ions can be either positively charged (Cations) or negatively charged (Anions).
IR drop - The voltage drop across a battery due to its internal impedance. See also Ohmic loss below.
Joule - “J” A measure of work, energy or cell capacity. For electrical energy, one Joule is one Amp at one Volt for one Second, or one WattSecond. 1 Wh = 3.6kJ. For mechanical energy one Joule is a force of one Newton acting over one metre i.e. One newton metre.
Leakage - The escape of electrolyte to the outer surface of the battery or 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.
Load current - The discharge current provided by a battery, or drawn by a battery powered device.
MSDS - Material Safety Data Sheet. Information provided by battery or cell manufacturers about any hazardous materials used in their products.
Negative Delta V (NDV) - The NDV is the drop in the battery voltage which occurs when NiCad or NiMH cells reaches their fully charge state. Used to detect the end of the charging cycle in Nicads.
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.
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.
Oxidation - The loss of electrons by a chemical species
Parallel connection - Connection together of the cell terminals of the same polarity of two or more cells to form a battery of higher capacity.
Permanent charge - The charging current which can safely be continuously supported by the battery, regardless of the state of the charge.
Peukert’s equation - An empirical formula that approximates how the available capacity of a battery changes according to the rate of discharge. The equation shows that at higher currents, there is less available energy in the battery.
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.
Pilot Cell - A selected cell whose condition is assumed to indicate the condition of the entire battery.
Polarity reversal - Reversal of the polarity of a battery or cell due to over discharge.
Primary battery - A battery that is non-rechargeable.
Pulse charger - Versatile, hybrid charger having some of the advantages of both switch-mode and linear chargers. More costly than both.
Pulse discharge - A high rate discharge, usually of 1 second or less.
Quick charge - Charging in three to six hours at about 0.3C rate. Needs special charger.
Rate - When applied to cells it usually means the cells current carrying capacity.
Rated capacity - The specified capacity of a battery.
Recycling - Reclamation of materials without endangering human health and the environment.
Reserve capacity - The number of minutes at which the battery can be discharged at 25 Amps and maintain a terminal voltage higher than 1.75 volts per cell, on a new, fully charged battery at 80degrees Fahrenheit(27C). Defines a battery’s ability to power a vehicle with an inoperative alternator or fan belt. Used for comparing automotive SLI batteries.
Resistance welding - Resistance welding is a process used to join metallic parts with electric current. There are several forms of resistance welding, including spot welding, seam welding, projection welding, and butt welding.
RFI - Radio Frequency Interference. Transmitted/emitted RFI affects other external equipment. Susceptibility measures the immunity of equipment from received RFI. See also EMC
Safety vent - A safety mechanism that is activated when the internal gas pressure rises above a normal level.
Sealed cells - A cell which remains closed and does not release gas or liquid when operated within the limits of charge and temperature specified by the manufacturer. An essential component in recombinant cells.
Self-discharge - Capacity loss during storage due to the internal current leakage between the positive and negative plates.
Series connection - The connection of positive to negative of two or more cells to form a battery of higher voltage.
Shunt regulator - A voltage regulator which uses a transistor or FET, in parallel with the load, which shorts out the excess voltage when the applied input voltage exceeds a specified limit producing a regulated output voltage. It is a simple but lossy design.
Slow charge - Charging overnight in 14 to 16 hours at about 0.1C rate. Safe and simple.
Solar cell - A photovoltaic cell. Solar cells convert sunlight energy into electric current. They do not store energy.
Solar panel - An array of photocells providing an increased output.
Solid State Battery - Cells with solid electrolytes. Lithium polymer cells are examples of this technology
Specific Gravity SG - The ratio of the weight of a solution compared with the weight of an equal volume of water at a specified temperature. It is used to determine the charge condition in lead acid batteries.
Standard charge - The normal charge used to recharge a cell or battery in 10 hours. Other definitions (charging periods) also apply.
Standby power - A fully charged battery ready to take over supplying a load in case of emergency.
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. See also Battery Storage
Studs - Threaded bolt connectors used on high power cells
Sulphation - Growth of lead sulphate crystals in Lead-Acid batteries which inhibits current flow. Sulphation is caused by storage at low state of charge.
Swelling - Distortion of cells caused by expansion of the active chemicals due to temperature and pressure effects.
Temperature sensor - An electronic device which provides a voltage analogue of the temperature of the surface on which it is mounted. A thermistor is an example.
Termination voltage - The maximum voltage which can be tolerated by a cell during charging without damaging the cell. The cell voltage at which the charging process should be terminated.
Thermal fuse - A safety device which interrupts a circuit when it detects excessive temperature.
Thermal imaging - A photographic technique which displays the range of temperatures of a warm body in the form of a colour spectrum. Used as a design verification tool for detecting hot spots in battery and other equipment designs.
Thermal management - The means by which a battery is maintained within its operating temperature limits during charging and discharging.
Thermal runaway - A condition in which an electrochemical cell will overheat and destroy itself through internal heat generation. This may be caused by overcharge or high current discharge and other abusive conditions.
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.
UPS - Uninterruptible Power Supply
Venting - The release of excessive internal pressure from a cell in a manner intended by design to preclude explosion.
Voltage cutoff - A voltage sensing device which will end a charge or discharge at a preset voltage value.
Voltage limit - A voltage value a battery is not permitted to rise above on charge and/or fall below on discharge
Voltage regulator - A circuit which provides a fixed or controlled voltage output from a variable voltage input. Used in power supplies and chargers. Switching regulators , Linear regulators and Shunt regulators are the most common types.
Voltaic efficiency - The ratio (expressed as a percentage) between the voltage necessary to charge a secondary cell and the corresponding discharge voltage.
VRLA battery - Valve Regulated Lead Acid Battery
Watt - A unit of power, the rate of doing work. Watts = Amps X Volts = One Joule per second.
Wet Cell - A cell with free flowing liquid electrolyte.