single electrochemical unit which exhibits a voltage across its two terminals and is used as the elementary unit of a battery module (3.1.30) or battery system (3.1.32)      [SOURCE: EASA, Third publication of means of compliance with the Special Condition VTOL] [14]

energy content expressed in watt-hours (Wh) and defined as the nominal battery voltage (V) times the capacity in ampere-hours (Ah) (3.1.14)   [SOURCE: RTCA, RTCA DO-311A, Minimum operational performance standards for rechargeable lithium batteries and battery systems [9]

amount of energy that a battery can store per unit of volume or mass, providing an indication of the capacity of a battery to store electrical energy   NOTE 1 Energy density of a battery is typically measured in watt-hours per unit volume or mass, e.g. watt-hours per kilogram. NOTE 2 High energy density is desirable for applications that require a compact and lightweight energy storage solution with a large capacity. NOTE 3 Energy density is distinct from power density, which

electronic system designed to monitor, manage and control the individual battery cells within a battery system (3.1.32)   NOTE 1 BMS components include, but are not limited to, cell monitoring sensors, control algorithms, communication interfaces, safety features, and thermal management systems. NOTE 2 The BMS is a critical component of the energy storage system (ESS) (3.1.69). NOTE 3 While the BMS is focused on the management of individual cells within a battery system, the 

group of electrically interconnected cells in series and/or parallel arrangement contained in a single enclosure that ensures that no fluids, flames, gasses, smoke, or fragments enter other modules, and that no thermal runaway is propagated from one module to the others during normal operation or failure conditions   [SOURCE: EASA, Third publication of means of compliance with the Special Condition VTOL] [14]

amount of power that a battery can deliver per unit of volume or mass, providing an indication of how quickly a battery can be charged or discharged   NOTE 1 Power density of a battery is typically measured in watts per unit volume or mass, e.g. watts per kilogram. NOTE 2 High power density in batteries is desirable for applications that require rapid charging and discharging. NOTE 3 Power density is distinct from energy density, which is more relevant for applications that p

assembly of electrically interconnected battery modules (modularized battery) or cells in series and/or parallel, plus any protective, monitoring, alerting circuitry or hardware inside or outside of the battery, its packaging, and the designed venting provisions   [SOURCE: EASA, Third publication of means of compliance with the Special Condition VTOL] [14]

thermal runaway of two cells that thermally affect at least one common adjacent third cell within the same battery or, for modularized batteries, within the same module; or thermal runaway of any three or more cells within the same battery or, for modularized batteries, within the same module   [SOURCE: EASA, Third publication of means of compliance with the Special Condition VTOL] [14]

system designed to regulate and control the temperature of a battery, or for modularized batteries, the battery module, in order to optimize its performance, enhance safety and extend its lifespan   NOTE Components of a battery thermal management system include, but are not limited to, temperature sensing and monitoring, cooling and heating systems, thermal insulation and thermal control algorithms.

measure used to express the rate at which a battery is charged or discharged in relation to its capacity   NOTE 1 For example, if a battery has a useful capacity of 10 ampere-hours (Ah), and its C rate is 1C, it can be charged or discharged at a rate of 10 amperes. If the C rate is 2C, it can be charged or discharged at a rate of 20 amperes and so on. NOTE 2 C rates are commonly used in the context of lithium-ion batteries and other rechargeable battery technologies. NOTE 3 C

rapid self-sustained heating of a battery cell (3.1.26) driven by exothermic chemical reactions of the materials within the cell   [SOURCE: EASA, Third publication of means of compliance with the Special Condition VTOL] [14]

document issued by the aircraft’s state of registry when satisfied that an aircraft conforms to an approved design and is in a condition for safe operation   NOTE With regard to UAS (3.1.137) the complete system is required to conform to its type design and be in a condition for safe operation.

set of processes by which an aircraft, remote pilot station, engine, propeller or part conforms to the applicable airworthiness requirements and remains in a condition for safe operation throughout its operating life   NOTE 1 “Remote pilot station” is synonymous with the term “command unit”, which is more commonly used in the UK and EU. NOTE 2 In the context of airworthiness, “part” refers to any element of a product, as defined by that product’s type design, and “product” refers

aircraft where either the safe lift-off and touchdown forward speed exceeds 45 knacross the ground, or the maximum forward speed for emergency touchdown exceeds 60 kn across the ground   NOTE 1 All VTOL-capable aircraft (3.1.143) are able to take-off and land vertically. Some also have the additional capability to take-off or land as conventional aeroplanes, accelerating and/or decelerating on a runway. NOTE 2 CTOL aircraft design conditions include additional, more stringent cons

number of complete charge and discharge cycles that a rechargeable battery can undergo before its capacity significantly degrades