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Glossary For Energy Storage

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AC

Alternating current; current flows in both directions. Household current is AC. 

Acid

Compound in a battery that promotes electro chemical reaction

Ampere-hours

Symbol Ah is a unit of charge. Example: Drawing a current of one ampere (1A) from a battery for one hour (1h) equates in one ampere-hour (1Ah).

Anode

Electrode on which oxidation occurs; releases electrons on discharge. When applying power to a device (vacuum tube, diode, battery on charge), the anode is positive; taking power away on discharge turns the anode to negative.

Barrel

Measuring unit for liquids (oil); 1 barrel has 42 US gallons, 35 Imperial gallons, 159 liters.

Battery

Electrochemical cell, or cells, connected in series (some in parallel); composed of the anode (negative electrode), cathode (positive electrode), separator and electrolyte as catalyst

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BMC

Battery management system used inside or outside a battery to manage charge, discharge and provide SoC; forms an essential part to assure battery longevity and safety

Battery Cycle

Charge followed by a discharge and recharge. No standard exists as to level of charge and discharge to constitute a cycle, but Energsoft is treating it as one Charge and Discharge

Capacitor

Component consisting of two conductive surfaces separated by an insulator. Passes AC; indefinite resistance for DC; voltage lags behind the current (opposite of a coil).

Capacity

Electrical charge of battery in ampere-hours (Ah). The stored energy is measured by observing the elapsed time while discharging at a constant current to the end-of-discharge voltage. The capacity is the leading health indicator of a battery

Cathode

Electrode in an electrochemical cell in which reduction takes place by absorbing electrons. During discharge, the cathode is positive; reverse on charge.

Coulomb

Unit of electric charge. One coulomb (1C) equals one ampere (1A) per second.

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Coulombic efficiency

also called faradaic efficiency or current efficiency describes the charge efficiency by which electrons are transferred in a batteries

C-rate

Unit by which charge and discharge times are scaled. At 1C, the battery charges and discharges at a current that is at par with the marked Ah.

Cycle life

Number of cycles a battery can deliver (End of battery life for portable devices is commonly set to 80%)

DC

Direct current; current flows in one direction. A battery delivers a DC current.

DoD

Depth of discharge; 100% is full discharge; 80% commonly used for specification.

EIS

Electrochemical impedance spectroscopy (EIS), also known as impedance spectroscopy; method to test electrochemical characteristics of a battery; EIS injects AC signals at different frequencies and analyzes the response.

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Electrode

Conductor or plate in a cell in which an electrochemical reaction occurs

Electrolyte

Non-metallic conductor of electricity (typically liquid) placed between positive and negative electrodes of a battery. Ion movement enables current flow.

Energy

Work measures over time. Multiplying voltage * current * time = Watt-hour (Wh). Energy is also given in joules (J); 1000 joules are 0.277 Wh. 

Energy density

Also known as volumetric energy density; specifies the amount of energy a cell can hold in volume (WH/1). Energy density is synonymous with the runtime of a battery.

Energy Star

Organization promoting energy efficiency.

Fuel gauage

State of charge (SOC) indicator to estimate the charge level of a battery

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IEC 60079

Intrinsically safe standards to prevent explosion in areas of flammable gas and dust.

EIC 60086

Safety standard for primary batteries

EIC 62133

Safety requirements for sealed secondary cells/batteries for portable use

IEEE 1625

Standard for rechargeable batteries for mobile computing devices

IEEE 1725

Standard for rechargeable cells/batteries for mobile phones.

Imaginary impedance

Also known as complex impedance; characterizes the electrical resistance of reactive components as a function of frequency. Rising frequency lowers the capacitve resistance and increases the inductance resistance.

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Impedance

Combination of capacitive, inductive and ohmic resistance; measured in ohms (R) frequency dependent.

Internal resistance

Electrical resistance of a battery pack in milliohmths. A good battery has low resistance; corrosion raises it.

Lead acid battery

Oldest rechargeable battery; used as starter battery wheeled mobility, UPS etc.

Lithium-ion battery

Rechargeable battery with cobalt, manganese, nickel and/or other metals as cathode and graphite anode.

Lithium (Li)

Soft, silver-white metal belonging to the alkali metal group, lightest and least dense metal in the element family; discovered by Johan August Arfwedson in 1817; metal is named after the Greek word "lithos" meaning "stone".

Pouch cell

Packaged into a flexible, heat-sealable foil pouch similar to wrapping food products.

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Power

Voltage * current = power in watts (W). Also in horsepower (1hp = 746W)

Ragone chart

Plots battery performance on specific energy versus specific power.

Resistance

Restriction to current flow; high resistance generates voltage drop and heat.

SAE J537

Test standard for 12V automotive starter batteries

SAE J1634

Test standard for electric vehicle; energy consumption, range.

SAE J1772

North American standard for electrical connectors for electric vehicles

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Separator

Isolates cathode and anode in a battery; acts as catalyst to promote ion movement from cathode to anode on charge and in reverse on discharge.

SMBus

System management Bus is a two-wire interface based on I2C; communicates with the battery and device by accepting control parameters and providing battery status, such as state-of-charge, manufacturer information, cycle count and error messages

Spectroscopy

Analysis of a compound or a battery when scanned with a frequency.

State of charge (SOC)

Indicates charge level of a battery; normally measured in percent. SoC has no relationsihip with capacity

State of function (SoF)

Reflects battery readiness that verifies capacity, current delivery, voltage, SoC, self-discharge and more; measured in %. Capacity, current delivery and SoC are most basic.)

State of health (SOH)

Reflects battery performance that verifies capacity, current delivery, voltage and self-discharge; measured in %. SoH exludes SoC.

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Sulfation

Formation of lead sulfate crystal in a lead acid battery that inhibits current flow; storage at low state of charge causes this.

Super-capacitor

Electrochemical capacitor also known as an ultracapacitor or double-layer capacitor; specific energy is a fraction of Li-ion. Has high cycle life; offers good cold temperature performances.

UL 1642

Safety acceptance test for lithium-based batteries by underwriters Laboratories. Other agencies are IEC 62133, EIII 1625, IEEE 1725, BAJ (Japan), UN. In 2010, UL 1642 transitioned to EIC 62133, made fully effective on 1 May 2012.

UN 38.3

Safety norms for shipping battery products

Voltage (V)

Electric energy potential per unit charge. 1V = 1 J / Coulomb. (1000 joules = 0.277 Wh). Watt (W) unit of power, ampere (A) * volt (V) equals watts (W).

Watt hour (Wh)

Unit of electrical energy equivalent to a power consuption of one watt for one hour. (One watt-hour = 3600 Joules). Multyplying a battery voltage (V) by the rated capacity (Ah) gives the battery energy in Wh. Example: 14.4V * 2.5 Ah = 36 Wh.