Glossary For Energy Storage

Energy Storage and Batteries


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


Compound in a battery that promotes electro chemical reaction


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).


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.


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


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

Battery Health Management


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


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).


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


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


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

Fancy Battery Cells Development

Coulombic efficiency

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


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%)


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


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


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.

Battery Selection and BenchMarking


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


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


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

Battery Energy and Helth Prediction

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.

Battery Cell Management


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.

Battery Pack Analytics


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

Ragone chart

Plots battery performance on specific energy versus specific power.


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

Battery Data Management


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.


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


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.

Lithium-Ion Battery in the Electrical Vehicle


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


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.