---
title: "ETSO-C173a — CS-ETSO · Avioverse"
description: "Nickel-Cadmium, Nickel Metal-Hydride, and Lead-Acid Batteries 1 Applicability This ETSO provides the requirements which Nickel-Cadmium, Nickel…"
url: "https://avioverse.aero/regulations/easa/cs-etso/subpart-b/etso-c173a"
---

# ETSO-C173a

European Technical Standard Orders (CS-ETSO) · CS-ETSO · EAR revision 1 Oct 2026

IR Implementing rule

## ETSO-C173a

Nickel-Cadmium, Nickel Metal-Hydride, and Lead-Acid Batteries

1 Applicability

This ETSO provides the requirements which Nickel-Cadmium, Nickel Metal-Hydride, and Lead-Acid Batteries that are designed and manufactured on or after the applicability date of this ETSO must meet in order to be identified with the applicable ETSO marking.

2 Procedures

2.1 General

Applicable procedures are detailed in CS-ETSO, Subpart A.

2.2 Specific

None.

3 Technical Conditions

3.1 Basic

3.1.1 Minimum Performance Standard

Standards set forth in the RTCA DO-293A, Minimum Operational Performance Standards (MPS) for Nickel-Cadmium, Nickel Metal-Hydride, and Lead-Acid Batteries, dated 12/2/2009, as amended according to Appendix 1 to this ETSO.

3.1.2 Environmental Standard

Nickel-Cadmium, Nickel Metal-Hydride, and Lead-Acid Batteries shall be tested according to the conditions specified in RTCA DO-293A.

Where the RTCA DO-293A quotes the RTCA DO-160 standard, the applicable DO-160 standard revision is defined in CS-ETSO, Subpart A, paragraph 2.1.

3.1.3 Computer Software

See CS-ETSO, Subpart A, paragraph 2.2.

3.1.4 Electronic Hardware Qualification

See CS-ETSO, Subpart A, paragraph 2.3.

3.2 Specific

None.

3.2.1 Failure Condition Classification

See CS-ETSO, Subpart A, paragraph 2.4.

4 Marking

4.1 General

Marking as detailed in CS-ETSO, Subpart A, paragraph 1.2.

4.2 Specific

At least one major component shall be marked permanently and legibly with all the information in RTCA DO-293A, section 1.10, as modified by Appendix 1.

5 Availability of Referenced Document

See CS-ETSO, Subpart A, paragraph 3.

\[Amdt ETSO/11]

IR · ETSO-C173a — CS-ETSO · ED Decision 2016/013/R · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026

Appendix Appendix

## Appendix 1 to ETSO-C173a Appendix 1 TO ETSO-C173a – Minimum Performance Standard for Nickel-Cadmium, Nickel Metal-Hydride, and Lead-Acid Batteries Amendment to RTCA DO-293A Requirements

| RTCA/DO-293A section and title:            | Amendment:                                                                                                                                                                                                                                             |
| ------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| 1.10.1, Battery Marking                    | It shall be added to the bottom of the list of Manufacturer’s markings: 11. End Point Voltage (EPV)                                                                                                                                                    |
| 2.3.1, Rapid Discharge Capacity at 23 °C   | It shall be deleted at the end of the paragraph and the Test Method: ‘or the manufacturer recommended cutoff voltage’                                                                                                                                  |
| 2.3.2, Rapid Discharge Capacity at – 30 °C | It shall be deleted at the end of the paragraph and the Test Method: ‘or the manufacturer recommended cutoff voltage’                                                                                                                                  |
| 3.12, Electrolyte Resistance               | It shall be applied ONLY to heater blankets of this section the following: Testing method and evaluation criteria of MIL-PRF-8565 can be utilised in lieu of the testing method and evaluation criteria stipulated in paragraph 3.12 of RTCA /DO-293A. |

\[Amdt ETSO/11]

APPENDIX · Appendix 1 to ETSO-C173a — CS-ETSO · ED Decision 2016/013/R · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026

[All rules in SUBPART B – LIST OF ETSOs](https://avioverse.aero/regulations/easa/cs-etso/subpart-b)

Consolidated from the EASA Easy Access Rules (revision 1 Oct 2026, extracted 13 Oct 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.