Definitions (BU65) Ambient temperature: The average temperature of the battery's surrounding medium, typically air. Ampere-hours (Ah): A measure of energy that is provided to or drawn from a battery. (A current of one ampere for one hour equals 1Ah). Battery cycle: A full charge followed by a full discharge (or the other way around). Button cell: A miniaturized battery. Most rechargeable button cells are NiCd or NiMH. C-code: Abbreviation of 'configuration code.' This information is typically stored in a battery adapter and configures the analyzer to the correct battery settings when installed. C-rate: Unit by which charge and discharge times are scaled. A battery rated at 1000mAh provides 1000mA for one hour if discharged at 1C. A discharge of 1C draws a current equal to the rated capacity. The same battery discharged at 0.5C would provide 500mA for two hours. Capacity: The electrical energy content of a battery as expressed in ampere-hours. Capacity is the total number of ampere-hours or watt-hours that can be withdrawn from a fully charged cell or battery under specific condition of discharge. The capacity is measured by observing the time it takes to discharge a battery at a constant current until a specified cut-off voltage is reached. Capacity offset: A correction factor applied to the rating of a battery if discharged under different C?rates from the one rated. Cell mismatch: Cells within a battery pack containing different capacity and voltage levels. Cell reversal: The stronger cells of a battery (several cells connected in series) impose a voltage of reverse polarity across a weaker cell during a deep discharge. Charge: The process of replenishing or replacing the electrical charge in a rechargeable cell or battery. Co-generation: The utilization of heat produced as byproduct in converting oxygen and hydrogen to electricity in a fuel cell. The heat is used to drive steam turbines. Coulomb: A unit of electric charge used to measure the ingoing and outgoing discharge current of a battery. One coulomb (1C) is equal to the electricity transferred by a current of one ampere in one second. (The maximum energy a molecular weight of a chemical system can deliver is one faraday of energy or 96495.7C which is the equivalent of 26.8Ah of capacity.) Coke: Coal from which most of the gases have been removed by heating. Coke is used as an industrial fuel. Current-limiting chargers: A charger that keeps the charge current constant during the charge process but allows the voltage to fluctuate (typically used on NiCd and NiMH chargers). Cycle: A process consisting of a single charge and discharge of a rechargeable battery. Cycle life: The number of cycles a battery provides before it is no longer usable. (A battery is considered non-usable if its nominal capacity falls below 60 to 80 percent). Cylindrical cell: The positive and negative plates are rolled up and placed into a cylindrical container. Double layer capacitor: Capacitor with high farad rating. The high capacity is made possible by a double layer formed near the carbon electrode surface. Dumb battery: A battery which contains no electronic circuitry with which to communicate digitally. Electrochemical Impedance Spectroscopy (EIS): Used to investigate electrochemical characteristics of batteries. The method applies an AC potential at varying frequencies to an electrochemical cell and the current response is measured. Electrode: Conducting element within a cell in which an electrochemical reaction occurs. Normally includes active materials plus conductive and supportive elements. Electrolyte: A non-metallic conductor of electricity (typically liquid) between the positive and negative electrodes of a battery. The current is carried by the physical movement of ions. Energy: Voltage multiplied by current expressed in watts. Energy density: The amount of energy a cell can contain. Gravimetric energy is the watt-hours a battery is capable of providing per given weight (pound or kilogram), and volumetric energy is the watt-hours per given size (cubic inch or cubic centimeter). The energy is defined as nominal battery voltage multiplied by rated capacity. Equalizing Charge: With time, the charge levels of individual cells of a large battery tend to become slightly unbalanced. The equalizing charge applies an elevated charge voltage for a few hours to balance the cells. Used mainly for large lead acid cells. Exercise: Commonly understood as one or several discharge cycles to 1V/cell with subsequent recharge. Used to maintain NiCd & NiMH batteries. Fast charge: Typical fast charge time for a nickel-based battery is 1 hour; lithium-based is 3 hours. The fast-charger detects the state-of-charge and switches to trickle charge when full-charge is reached. Float charge: Similar to trickle charge. Compensates for the self-discharge on a lead acid battery. Fuel cell: An electrochemical device that generates electricity by converting oxygen and hydrogen into water. Fuzzy logic: A mathematical technique used to obtain an approximate output reading derived from various analog inputs. Fuzzy logic can be utilized to quick-test batteries. Graphite: A form of carbon. Hydrogen battery: A rechargeable battery commonly used for space applications. Internal resistance: Resistance to electrical current inside a cell or battery pack. Impedance: Resistance to electrical current created by reactance and ohmic resistance Intelligent battery: Also known as a 'smart' battery. The battery pack contains internal circuitry to enable communication between the battery and the user. Intrinsically Safe: A battery with built-in protection circuitry. These batteries are used primarily in explosive environments. Ion: A charged particle that is combined with a particle of opposite charge to produce a chemical salt. Lead acid battery: Rechargeable battery commonly used for wheeled and stationary applications. The plates consist of lead-antimony alloy. Lithium battery: A battery using lithium metal as negative electrode. Most lithium batteries are non-rechargeable. Lithium ion battery: A battery dependent on the flow of lithium ions. The lithium metal on the negative electrode is replaced with carbon to improve safety. Lithium ion polymer: A rechargeable battery similar to the Li?ion but with a solid polymer as electrolyte. Some gelled conductive material is added to promote conductivity. Lithium polymer: A rechargeable battery using solid polymer as electrolyte. Most lithium polymer batteries require heat to promote conductivity. Load current: The discharge current delivered to a battery-powered device. Matrix: The set of battery parameters stored in the battery adapter to enable the Cadex Quicktestä function. Manganese: A metallic chemical element. Maintenance Requirements: Battery maintenance prolongs battery life. Nickel-based batteries need a periodic full discharge to eliminate 'memory'. Lead acid batteries require periodic equalizing charge. Lithium-based batteries need little maintenance. Memory: Reversible capacity loss in NiCd and NiMH batteries. The modern definition of memory commonly refers to a change in crystalline formation from the desirable small size to a large size. Memory is often used to describe any reversible capacity loss on nickel-based batteries. Milliampere-hour: A battery capacity or rating. A battery that provides a current of 1000mA for 1 hour is rated at 1000mAh (or 1Ah). Negative delta V (NDV): A drop in battery voltage, which occurs when a sealed NiCd or NiMH battery reaches the full charge state and goes into overcharge. Nickel cadmium battery: A rechargeable battery using cadmium as the negative electrode. Nominal voltage: The cell voltage that is accepted as an industrial standard. (Cell voltages of 1.20 and 1.25V are used for NiCd and NiMH batteries). Ohmic resistance: Electrical resistance void of reactance. Ohmtest™: A measurement that reflects the internal resistance of a battery. Organic: Carbon-based solvent. Overcharge: Charging a battery after it reaches full charge. On overcharge, the battery can no longer absorb charge and the battery heats up. Passivation layer: A resistive layer that forms in some cells after prolonged storage. This layer must be broken to enable proper operation. Applying charge/discharge cycles often help in preparing the battery for use. Polymer: An ionic conductor that is an electrical insulator put passes ions. Pouch cell: A battery in which the typical metallic cylinder and glass-to-metal electrical feed-through is replaced with a flexible, heat-sealable foil package. Primary battery: A non-rechargeable battery. The active materials of a primary battery undergo an irreversible change during discharge. Prismatic cell: The positive and negative plates are stacked rather than rolled. Protection circuit: Circuitry built into the battery pack to maintain the safety of the battery and equipment in case of improper handling. Quick charger: A charger that charges a battery in 3 to 6 hours. Quicktest™: A method to quick test the state-of-health of a battery. Rapid charge: Same terminology as quick charger. Reactance: The presence of inductive and capacitive resistance. Recondition: A deep discharge below 1.0V/cell with a controlled current, causing a change to the molecular structure of the cell and a rebuilding of its chemical composition. Recondition helps break down large crystals to a more desirable small size, often restoring the battery to its full capacity. Applies to nickel-based batteries. Resistance: Opposition to electrical current flow. Batteries with high internal resistance are not able to deliver heavy current pulses or elevated loads. Residual capacity: The charge capacity remaining in a battery prior to charge. Reverse load charge: A charge method that intersperses discharge pulses between charge pulses to promote the recombination of gases generated during fast charge. Reverse load charge also helps to reduce memory. Secondary battery: A battery that is rechargeable by reversing its chemical reaction. Self-discharge: Capacity loss during storage due to the internal leakage between the positive and negative cell plates. Single wire bus: Simplified 'smart' battery using only one wire for digital communications to the outside world. Slow charge: Typically an over-night charge lasting 10 to 16 hours at a charge current of 0.1C. A battery does not require instant removal when fully charged. 'Smart' battery: Also known as an 'intelligent battery.' A battery pack containing internal circuitry that enables communication between the battery and the user. Soft cell: A cell whose voltage rises above its defined boundaries during charging. This voltage rise may be caused by high cell impedance, cold battery temperature or lack of electrolyte. Spectroscopy: Same terminology as Electrochemical Impedance Spectroscopy. Spinel: A family of compounds that have a specific chemical structure. In lithium-ion batteries, the structure is manganese-based. State-of-Charge (SoC): A measurement that reflects the state-of-charge of a battery. The SoC alone is not a valid indicator of the battery's runtime. The SoC readings will indicate 100 percent, even if a battery whose acceptance has dropped to 50 percent is fully charged. State-of-Health (SoH): A measurement that reflects the state-of-health of a battery, taking into account charge acceptance, internal resistance, voltage and self-discharge. Sulfation: The growth of lead sulfate crystals in lead acid batteries, which inhibits current flow. Sulfation is caused by storage at low state-of-charge. Supercapacitor: A capacitor that can store a high amount of energy. Supercapacitors hold about one tenth the energy of a nickel or lithium-based battery. System Management Bus (SMBus): A commonly used protocol for the 'smart' battery. Thermal battery voltage: Batteries are non-linear systems. The equations, which govern the battery's response, becomes linear below 25mV/cell at 25°C. This voltage is called the battery thermal voltage. Thermal runaway: A condition whereby 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: Maintenance charge to compensate for the battery's self-discharge. Topping Charge: To complete the fast charge, a topping charge is applied that continues charging the battery for 30 minutes or longer at a lower current. Typically used for nickel-based batteries. Voltage delay: During open circuit storage, some battery systems develop a passivation film on the surface of the active material. On the initial discharge, these batteries demonstrate a momentarily lower than normal voltage until this film is removed by the discharge. Voltage limit: The voltage value beyond which a battery is not permitted to rise on charge or fall on discharge. Voltage-limiting charger: A charger that limits the maximum voltage to a battery but allows the current to drop towards the end of charge. A voltage-limiting charge may also include current-limiting. (Typically used on lead acid and Li?ion battery chargers). Zapping: The process of applying a momentary high current pulse to a battery to improve performance. Zapping is said to improve new NiCd batteries but does not restore weak packs. _________________________ Created: March 2003, Last edited: March 2005 About the Author Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. Award winning author of many articles and books on batteries, Mr. Buchmann has delivered technical papers around the world. Cadex Electronics is a manufacturer of advanced battery chargers, battery analyzers and PC software. For product information please visit www.cadex.com. Click here for a printer-friendly version © Copyright 2003 - 2005 Isidor Buchmann
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