AC 2 0-184A Appendix G compliance with SO 1 and SO 2, the emitted gases must be collected and evaluated for the volume and constituents of the gas. This would provide the ability to evaluate the dissipation and hazard level of these emissions in the location in which the End Item is to be installed.
G.3.5.4 SO 4: Meet the requirements of § 23.2325(g).
Method of Compliance with SO 4:
1. Section 23.2325(g) requires minimizing the likelihood of a fire and the resultant hazards if fire does occur. Both battery electrolyte and any coolant fluid, if present, are considered fluid systems when evaluating § 23.2325( g).
2. Perform a safety assessment to identify and evaluate associated hazards and their severity. Mitigate and minimize all hazards resulting from a battery failure.
G.3.5.5 SO 5: Not damage surrounding structure or adjacent systems, equipment, components, or electrical wiring from corrosive or any other fluids or gases that may escape in such a way as to cause a major or more-severe failure condition.
Method of Compliance with SO 5:
1. Show that if fluid escapes the battery, it is not corrosive or it is managed in a way (e.g., contained, isolated, or vented overboard) to protect the surrounding structure and adjacent systems, equipment, components, and electrical wiring.
2. Evaluate test results after conducting tests per RTCA DO-311A, including a system safety assessment for failure conditions. Use test results of SO 1 and SO 2 for SO 5 substantiations. Mitigation at the airplane level may be applied to bring the design into compliance.
3. The intent is to show that if fluid escapes the battery during the testing for compliance with SO 1 and SO 2, it is not corrosive or it is managed in a way (e.g., contained, isolated, or vented overboard) to protect the surrounding structure and adjacent systems, equipment, and electrical wiring.
G.3.5.6 SO 6: Have provisions to prevent any hazardous effect on airplane structure or systems caused by the maximum amount of heat it can generate due to any failure of it or its individual cells.
Method of Compliance with SO 6:
1. Show that the effects of heat and any related effects from conducting tests per RTCA DO-311A do not create a hazard to the structure or systems of the airplane. The maximum heat to be considered must be equal to or greater than the heat generated from the worst-case thermal G-4
AC 2 0-184A Appendix G runaway containment test agreed to in this appendix ( e.g., tests performed for SO 1 and 2).
2. If the effects of the heat or any related effects constitute a hazard to the structure or systems of the airplane, mitigation at the airplane level may be applied to bring the design into compliance.
3. The temperature of the gases and the enclosure need to be provided.
This temperature will help show that the effects of the heat, and any related effects, from the tests performed under SO 1 and SO 2 do not constitute a hazard to the structure or systems of the aircraft.
G.3.5.7 SO 7: Have a failure sensing and warning system to alert the flightcrew if its failure affects safe operation of the ai rplane.
Method of Compliance with SO 7:
1. Ensure adequate flightcrew alerting because failure effects of a battery installation to airplane level functions could result in unsafe system operating conditions.
2. RTCA DO-311A, section 2.1.4.2, Battery Warning Features, discusses warning circuits and signals.
G.3.5.8 SO 8: Have a monitoring and warning feature that alerts the flightcrew when its charge state falls below acceptable levels if its function is required for safe operation of the airplane.
Method of Compliance with SO 8:
1. Have a means for the flightcrew and maintenance personnel to determine the battery charge state if the battery’s function is required for safe operation of the airplane.
2. Use a system safety assessment to determine the alert level.
G.3.5.9 SO 9: Have a means to disconnect from its charging source in the event of an over-temperature condition, cell failure, or battery failure.
Method of Compliance with SO 9:
1. In accordance with the applicable rules listed in paragraph 2.2.2, table 2-1, the battery must be capable of disconnecting itself from the charging source to prevent failure conditions, including satisfying SO 1 and SO 2.
2. Not applicable to the cases where RTCA DO-311A has protection disabled as a prerequisite for the test.
G.4 Method of Compliance for Very Small Rechargeable Lithium Batteries Less Than 2 Wat t-Hours.
Compliance with UL 1642, UL 2054, or IEC 62133 is an acceptable method of compliance to show §23.2525 that SO 1 – S O 6, and SO 9 requirements are met for G-5
AC 20-184A Appendix G very small button/coin rechargeable lithium battery installations with less than 2 watthours of energy.
G.5 ICA Required by § 23.1529, Appendix A to Part 23.
Include the following in the ICA, to comply with § 23.1529, a ppendix A to Part 23:
G.5.1 Maintenance requirements to replace each rechargeable lithium battery within an interval o r monitoring based on state of health that will ensure there is sufficient charge to power equipment.
G.5.2 A requirement to only replace rechargeable lithium batteries with batteries from the same manufacturer with the same part number or to obtain a new FAA approval for installing a different battery. Refer to the battery Original Equipment Manufacturer maintenance manual.
G.5.3 Procedures to ensure that each rechargeable lithium battery has not:
• Experienced degraded charge retention ability or other damage during storage.
• Been damaged from environmental or physical impacts such as mechanical shock, vibration, heat, and possible abuses encountered during storage, transportation prior to their installation or maintenance activities on or around them.
G.5.4 Precautions to prevent mishandling of replacement rechargeable lithium batteries prior to their installation that could result in short-circuit or other unintentional damage.
G.6 Uncontained Engine or APU Rotor Failures: §§ 23.2410 and 23.2510 at Amendment 23-64.
G.6.1 In general, as part of showing compliance with §§ 23.2410 a nd 23.2510, the FAA expects the applicant to demonstrate that a foreseeable event o riginating from outside of a rechargeable lithium battery, such as an uncontained rotor burst, will not compromise continued safe flight and l anding. You may use fail-safe design features that encase and safely vent the hazardous byproducts of a failure originated from within the battery to show compliance with the rechargeable lithium battery SOs. Depending on the location of the battery installation, a rotor failure could defeat such safety features. If a rechargeable lithium battery is installed in a rotor burst zone, ensure the means of compliance with the SOs remains effective considering potential rotor failures that could damage the battery.
G.6.2 Regarding compliance with § 23.2410 for turbine engine rotor failures, AC 20-128A provides guidance on fragmentation characteristics and the boundaries of the locations in which applicants are expected to evaluate the effects of impact damage following an uncontained rotor burst. For a rechargeable lithium battery—except for very small button/coin cells with less than 2 watt-hours of energy that meet UL 1642, U L 2054, or IEC 62133—assess the r otor-burst-induced damage to the battery in a plan for showing G-6
AC 20-184A Appendix G compliance with § 23.2410 in conjunction with complying with the rechargeable lithium battery SOs. Clearly state the method of compliance in your response to this section of the AC.
G.7 Lithium Battery Installed in a Designated Fire Zone (DFZ) (§§ 23.244 0 and
23.2510).
G.7.1 Installation in a DFZ should be avoided, but may be acceptable if the battery location does not create an additional hazard. The external fire threat to the battery when it is located in a DFZ is a 2000°F flame for 15 minutes per AC 20-135, Powerplant Installation and Propulsion System Component Fire Protection Test Methods, Standards, and Criteria. The heat generated by this flame may cause multiple cells to enter thermal runaway along with damage to the battery containment system resulting in uncontrolled fire or explosion.
G.7.2 In accordance with § 23.2440(c)(1) and any other applicable airworthiness regulation references in table 2-1 of AC 20-184A, the battery must contain or vent any thermal runaway and pr event introduction of additional hazards when exposed to a 2000°F flame for 15 minutes. Test by exposing the battery installation design (including any vents) to a 2000°F flame for 15 minutes per AC 20-135. Ensure no additional hazards are introduced. For all batteries installed in a DFZ, minimize the risk of fire in the DFZ.
Some examples are:
G.7.2.1 Directing and venting (if the design includes a vent) any potential flames or flammable material from the battery out of the fire zone. Any vent system included in the design must continue to function in the event of a thermal runaway of the battery, otherwise it must not create an additional hazard from its failure.
G.7.2.2 Using fireproof materials in the construction of the battery installation design.
G.7.2.3 Providing adequate shielding to protect the battery and vent, if any, from direct flames to ensure the battery remains below a temperature that could compromise the thermal runaway containment integrity when exposed to a powerplant fire condition.
G.8 Hazard Mitigations for Large Battery System Thermal Runaway Conditions.
Airplanes requiring high-capacity batteries may increase the severity level and adverse effects resulting from a battery thermal runaway condition or any other hazards. Using RTCA DO-311A, including articles approved under TSO-C179b, is an accepted approach for addressing the thermal runaway aspects of rechargeable lithium battery installations. All applicable airworthiness regulations must be addressed and complied with. RTCA DO-311A, as well as TSO-C179b, provide a testing standard and articlelevel approval that requires additional integration and mitigation strategies in order to G-7
AC 20-184A Appendix G fully comply with the applicable airworthiness regulations on the aircraft. The level of acceptable risk will be commensurate with the Part 23 level 1, 2, 3, or 4 aircraft. In addition, the FAA outlines guidance in paragraph G.8.1 to address verification aspects of lithium battery thermal runaway conditions for the RTCA DO-311A, s ection 2.4.5.5.
All other tests within RTCA DO-311A are applicable as stated in the industry consensus standard.
Note: Due to the significance of technical and regulatory issues, coordinate as soon as possible with the FAA.
G.8.1 Battery Thermal Runaway Containment Test (RTCA DO-311A, Section 2.4.5.5).
G.8.1.1 RTCA DO-311A, section 2.4.5.5, describes the test methods for battery thermal runaway containment that are designed to force the entire battery into a thermal runaway state. This may not be feasible for very large highcapacity systems. To address the feasibility of very large high-capacity battery system testing, this section of the AC defines a module or sub-pack as a battery system divided into smaller configurations to help in testing and validating the safety implication of the battery system. The battery and battery system can be designed into several smaller modules or sub-packs.
Each module has an assembly of cells electrically connected and enclosed in a single enclosure. Each sub-pack has an assembly of electrically connected modules that is enclosed by a single enclosure. The venting design of the sub-pack, module, and cells need to be considered in the mitigation strategy.
G.8.1.2 To successfully comply with the requirement of the RTCA DO-311A, section 2.4.5.5, test, it is acceptable to use a modularized/sub-pack battery system design.
Note: Coordinate as soon as possible with the FAA on the proposed design methodology (i.e., modularized/sub-pack battery system design).
G-8
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