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1、 Intermixing Cells in an Aircraft Nickel-Cadmium Battery Steven M. Summer November 2011 DOT/FAA/AR-TN11/16 This document is available to the U.S. public through the National Technical Information Services (NTIS), Springfield, Virginia 22161. This document is also available from the Federal Aviation
2、Administration William J. Hughes Technical Center at actlibrary.tc.faa.gov. U.S. Department of Transportation Federal Aviation Administration o ote technical note technicte technical note technica a NOTICE This document is disseminated under the sponsorship of the U.S. Department of Transportation i
3、n the interest of information exchange. The United States Government assumes no liability for the contents or use thereof. The United States Government does not endorse products or manufacturers. Trade or manufacturers names appear herein solely because they are considered essential to the objective
4、 of this report. The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the funding agency. This document does not constitute FAA policy. Consult the FAA sponsoring organization listed on the Technical Documentation page as to its use. Th
5、is report is available at the Federal Aviation Administration William J. Hughes Technical Centers Full-Text Technical Reports page: actlibrary.tc.faa.gov in Adobe Acrobat portable document format (PDF). Technical Report Documentation Page 1. Report No. DOT/FAA/AR-TN11/16 2. Government Accession No.
6、3. Recipients Catalog No. 4. Title and Subtitle INTERMIXING CELLS IN AN AIRCRAFT NICKEL-CADMIUM BATTERY 5. Report Date November 2011 6. Performing Organization Code 7. Author(s) Steven M. Summer 8. Performing Organization Report No. 9. Performing Organization Name and Address Federal Aviation Admini
7、stration William J. Hughes Technical Center 10. Work Unit No. (TRAIS) Airport and Aircraft Safety Research and Development Group Fire Safety Team Atlantic City International Airport, NJ 08405 11. Contract or Grant No. 12. Sponsoring Agency Name and Address U.S. Department of Transportation Federal A
8、viation Administration 13. Type of Report and Period Covered Technical Note Air Traffic Organization NextGen however, none of the cells exceeded the maximum voltage of 1.7 V. During some tests, individual cells showed some differences in behavior and recorded battery temperatures. The most notable d
9、ifference occurred during the induced destructive overcharge tests, in which a larger number of cells from the intermixed battery recorded increased voltage readings, indicating signs of thermal runaway. The results show no indication of any safety of flight issues arising from the intermixing of OE
10、M and PMA battery cells within a nickel-cadmium aircraft battery. 17. Key Words Nickel-cadmium battery, Battery cell, Thermal runaway, NiCd 18. Distribution Statement This document is available to the U.S. public through the National Technical Information Service (NTIS), Springfield, Virginia 22161.
11、 This document is also available from the Federal Aviation Administration William J. Hughes Technical Center at actlibrary.tc.faa.gov. 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages 19 22. Price Form DOT F 1700.7 (8-72) Reproduc
12、tion of completed page authorized TABLE OF CONTENTS Page EXECUTIVE SUMMARY vii INTRODUCTION 1 Background 1 Scope 1 EQUIPMENT AND PROCEDURES 1 Test Equipment 1 Test Procedures 3 Rated Capacity Test 4 Charge Stability Test 4 Duty Cycle Performance Test 4 Induced Destructive Overcharge Test 5 DISCUSSIO
13、N 5 SUMMARY 10 REFERENCES 11 iii iv LIST OF FIGURES Figure Page 1 Saft 4078-7 Aircraft Battery 2 2 Top View of the Saft 4078-7 Battery With Cover Removed 2 3 Average Charging Voltage of Cells During the Initial Rated Capacity Test 5 4 Recorded Battery Temperatures During the Duty Cycle Tests 7 5 Ave
14、rage Charging Voltage of Cells During the Repeated Rated Capacity Test 7 6 Charging Voltage, Current, and Battery Temperature During the Induced Destructive Overcharge Test for the OEM Battery 8 7 Charging Voltage, Current, and Battery Temperature During the Induced Destructive Overcharge Test for t
15、he Intermixed Battery 8 8 Cell Voltages for Cells Exceeding 2.0 V During the Induced Destructive Overcharge Test for the OEM Battery 9 9 Cell Voltages for Cells Exceeding 2.0 V During the Induced Destructive Overcharge Test for the Intermixed Battery 10 LIST OF ACRONYMS A Ampere Ah Ampere-hour CMM C
16、omponent Maintenance Manual EPV End point voltage FAA Federal Aviation Administration NiCd Nickel-cadmium OEM Original equipment manufacturer PMA Parts Manufacturer Approval V Volt Vdc Voltage direct current v/vi EXECUTIVE SUMMARY The Federal Aviation Administration (FAA) issues Parts Manufacturer A
17、pprovals (PMA) for aircraft replacement parts that are not manufactured by the original equipment manufacturer (OEM). To obtain a PMA, the replacement part manufacturer must meet the FAA requirements for safety regulations and standards, and it must meet the OEMs specifications and standards for the
18、 part it is replacing. Replacement battery cells within aircraft batteries are issued PMAs from the FAA under Order 8110.42C; however, some OEMs claim that intermixing PMA with OEM cells within an aircraft battery can have drastic effects on battery performance, thus causing a potential safety of fl
19、ight issue. Tests were performed at the FAA William J. Hughes Technical Center by the Fire Safety Team of the Airport and Aircraft Research and Development Group to determine if intermixing cells within an aircraft nickel-cadmium battery has an effect on battery performance or safety. For the purpos
20、e of these tests, two Saft 4078-7 aircraft batteries were used. This 20-cell, 43-ampere-hour (Ah) battery with a nominal voltage of 24 volts (V) is used to start the engine on the ground before onboard systems are normally supplied and in the case of faulty functioning or failure of normal power sup
21、ply while airborne. It is charged onboard using the aircrafts 28 Vdc electrical network. One of these batteries was kept in its original form with all OEM battery cells, while half the cells (10 cells) in the other battery were replaced with PMA replacement cells. A series of tests from RTCA/DO-293
22、were conducted on the two batteries, including several rated capacity tests, a charge stability test, a duty performance test, and an induced destructive overcharge test. Throughout the tests, only slight differences were observed between the OEM and intermixed batteries. The PMA cells consistently
23、charged at a higher voltage, however, none of the cells ever exceeded the OEM-specified maximum voltage of 1.7 V. The performance of both batteries was significantly diminished during the rated capacity test that was conducted at -22F, with the OEM battery having a capacity of 29.3 Ah and the interm
24、ixed battery having a capacity of 22.0 Ah. During one discharge cycle of the duty cycle test, the intermixed battery recorded a capacity of 42.1 Ah, which is below the rated capacity of the battery, but not below the test specification which requires 80% of capacity during this interval of the test.
25、 Other than these discrepancies, the recorded capacities for both batteries throughout the tests were very similar. The recorded battery temperature during the duty cycle test showed considerable differences. The OEM battery experienced significant temperature spikes of up to 138F, lasting for brief
26、 time periods. These temperature spikes occurred during the charge and discharge periods. In contrast, the intermixed battery experienced severe increases in temperature for prolonged time periods, occurring not only during the charge and discharge periods, but also during the cycling of the battery
27、. This temperature rise sometimes exceeded 168F. vii The overall performance of the two batteries during the induced destructive overcharge test was very similar, however, the individual cells showed some significant variations. Both batteries exhibited very large increases in current and battery te
28、mperature during the overcharge portion of the test. The OEM battery resulted in a maximum temperature of 257F and a maximum current of 170 amperes (A), while the intermixed battery resulted in maximum values of 274F and 164 A. The OEM battery contained 4 battery cells that exceeded 2.0 V during the
29、 test. Of those four cells, only one (cell 5) exceeded 10 V, indicating signs of thermal runaway. Other cells in the OEM battery exceeded 2.5 V. In comparison, the intermixed battery contained six battery cells exceeding 2.0 V. These cells consisted of four OEM and two PMA cells. Both PMA cells (cel
30、ls 5 and 6) exceeded 10 V. Only one OEM cell in the intermixed battery exceeded 10 V (cell 9), while all three of the other OEM cells exceeded 2.5 V (cells 4, 14, and 17). Neither battery exhibited any evidence of flames or explosions during this test; however, smoke emanated from both batteries as
31、the electrolyte within the cells evaporated due to the high temperatures. The observed smoke was similar in type and approximate volume for both batteries; following dismantling and inspection of the batteries, no evidence of any physical damage was found. The test results showed no indication of an
32、y safety of flight issues arising from the intermixing of OEM and PMA battery cells within a nickel-cadmium aircraft battery. viii INTRODUCTION BACKGROUND. The Federal Aviation Administration (FAA) issues Parts Manufacturer Approvals (PMA) under Order 8110.42C 1 for aircraft replacement parts that a
33、re not manufactured by the original equipment manufacturer (OEM). To obtain a PMA, the replacement part manufacturer must meet the FAA requirements for safety regulations and standards, and it must meet the OEMs specifications and standards for the part it is replacing. Replacement battery cells wit
34、hin aircraft batteries are issued PMAs from the FAA; however, there have been claims from OEMs that intermixing PMA with OEM cells in an aircraft battery can have drastic effects on battery performance and may cause a safety of flight issue. There is also some confusion within the FAA regulations as
35、 to what practices are acceptable relative to PMA cells. Technical Standard Order C173 2 is the document that specifies the minimum performance standards required for nickel-cadmium (NiCd) and lead-acid batteries. This document specifies that these batteries must adhere to the conditions specified i
36、n RTCA/DO-293 3. DO-293 states in paragraph 1.5.1.2, subparagraph b that, “mixing of cells or batteries is not an acceptable practice.” It further states that, “Cells or batteries may have different capacities because they have different designs, manufacturing processes or storage, use or age histor
37、ies. Therefore, mixing cells or batteries with different part numbers, made by different manufacturers or from different sources, is a non acceptable practice.” These statements, referenced by the applicable Technical Standard Order 2, clearly advise against the intermixing of cells, yet based on Ch
38、apter 1, section 5b of Order 8110.42C, PMA replacement cells are permissible. SCOPE. Tests were performed at the FAA William J. Hughes Technical Center by the Fire Safety Team of the Airport and Aircraft Safety Research and Development Group to determine if intermixing cells within an aircraft NiCd
39、battery has an effect on battery performance, and if any such effect results in a safety of flight issue. EQUIPMENT AND PROCEDURES TEST EQUIPMENT. Two Saft 4078-7 aircraft batteries were used for these tests (figure 1). This 20-cell, 43-ampere- hour (Ah) battery with a nominal voltage of 24 volts (V
40、) is used to start the aircraft engine on the ground before onboard systems are supplied normally and in the case of faulty functioning or failure of normal power supply while airborne. It is charged onboard using the aircrafts 28-Vdc electrical network. One battery was kept in its original form wit
41、h all OEM battery cells, while half the cells in the other battery were replaced with PMA replacement cells. Throughout this report, these will be referred to as the OEM battery and the intermixed battery, respectively. Figure 2 shows a top view of the battery with the top cover removed. The cells a
42、re numbered 1 through 20 based on their order of interconnection within the battery. Cells 1, 3, 5, 6, 8, 10, 1 12, 15, 18, and 20 were replaced with PMA cells in the intermixed battery and are denoted in figure 2 by a red square around the cells number. Figure 1. Saft 4078-7 Aircraft Battery 12 14
43、13 15 10 11 8 16 4 5 6 9 17 7 18 3 19 2 20 1 Figure 2. Top View of the Saft 4078-7 Battery With Cover Removed (The cells are numbered with the PMA cells denoted by the red squares around the numbers.) 2 The two batteries were initially serviced as though they were being commissioned for service onbo
44、ard an aircraft. This included the following procedures: 1. Battery case and cells are visually inspected for signs of damage. 2. Battery cover is removed for internal inspection of cells and verification of correct cell polarity. 3. Cell vents are inspected. 4. Check cell-to-case insulation. 5. Tor
45、que is checked on all hardware. 6. Temperature sensor blanket is inspected for signs of wear. 7. Cannon plug pins are checked. 8. Condition of connector is inspected. 9. Cells are charged per instructions in the Component Maintenance Manual (CMM). 10. Electrolyte levels are adjusted. 11. Any spilled
46、/bubbled electrolyte is cleaned. 12. Case cover is closed. An Arbin Instruments BT2000 battery analyzer was used to conduct the required tests on the batteries, which included various forms of charging, discharging, and cycling of the batteries. This analyzer had a voltage range of 0-50 V and a curr
47、ent range of 0-400 ampere (A). It also provided the ability to monitor and record voltage data from each of the 20 cells, with a range of 0-10 V, and up to 12 temperature measurements by means of externally connected K-type thermocouples. Supplied software on a computer connected to the BT2000 contr
48、olled the analyzer charging and discharging rates and allowed for any number of test steps or cycles to be programmed by the user. TEST PROCEDURES. A series of tests from DO-293 were conducted on each battery to evaluate any effect that the intermixing of cells may have on battery performance. The t
49、est sequence was as follows: 1. Rated Capacity (DO-293, test 2.2.2) 2. Rated Capacity at -22F (DO-293, test 2.2.4) 3. Rated Capacity at 122F (DO-293, test 2.2.5) 4. Charge Stability (DO-293, test 2.6) 5. Duty Cycle Performance (DO-293, test 2.10) 3 6. Rated Capacity (DO-293, test 2.2.2) 7. Induced Destructive Overcharge (DO-293, test 2.14) Each test is discussed in the following sections. The complete test specifications are found in DO-293. The charging or discharging rate is referred to as the C-rate. For a battery with a capacity of 43 Ah, such
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