1 

J i NASA-TM-87415 19850012223 

; i 

, ! 

\~-------------------

" :' '::,~lDeJ:ge'ncYi.9catot,Transmitter(EL T) 

,': >: Battetles'dtJidanCeanCl,Recommendations 

'lIBRARY,(ORV:; , 

JAN: 2 Wt ',,::, :; 

': 'DOCUMENTNO.RTCAlDO-188 , . " ." .. ,.,." , " 

, ... ; :; Noveinber1984 ; ". ' 

," . ,p~~Pafed,~yi,s~1,~6, ELT' 

. ~attery Subcommittee ' , , , , ~ , 

.,;"., ,,"' 
RADIO TECHNICAL COMMISSION FOR AERONAUTICS 

One McPherson Square 

1425 K Street, N.W., Suite 500 

Washington, D.C. 20005 

Emergency Locator Transmitter (ELT) Batteries 

Guidance and Recommendations 

RTCA/DO-188 

November 13, 1984 

Prepared by: 

SC-l36 ELT 

Battery Subcommittee 
Copies of this document may be obtained from 

RTCA SECRETARIAT 

One McPherson Square 

1425 K Street, N. W. 

Suite 500 

Washington, D. C. 20005 

(202) 682-0266 

$25.00 

(50% Discount to RTCA Members & International Associates) 

NOTE: All orders for RTCA documents shall be accompanied by payment to 

include shipping and handling fees. These documents will be sent 

First Class or Priority Mail in the United States, Canada and 

Mexico. Shipments to other countries will be by International AO 

Mail. The fee to be added to the basic cost of each document is 

~3.00 for delivery in the United States, Canada and Mexico, and 

~6.00 for other countries. Members and International Associates 

are entitled to a 50% discount on documents, but the full shipping 

and handling fee is required for each document ordered. Please 

remit in U.S. funds directly to RTCA. 
FOR E W 0 R D --------

This report was prepared in response to a request from the 

Federal Aviation Administration who had indicated a concern about ELT 

battery-related problems. A subcommittee of RTCA Special Committee 

136 was tasked to investigate these problems as specified in the 

Statement of Work on page v. The RTCA Executive Committee approved 

the Report of the ELT Battery Subcommittee on November 13, 1984. 

RTCA is an association of aeronautical organizations of the 

United States from both government and industry. Dedicated to the 

advancement of aeronautics, RTCA seeks sound technical solutions to 

problems involving the application of electronics and 

telecommunications to aeronautical operations. Its objective is the 

resolution of such problems by mutual agreement of concerned 

organizations. 

The findings of RTCA are in the nature of recommendations to all 

organizations concerned. As RTCA is not an official agency of the 

United States Government, its recommendations may not be regarded as 

statements of official government policy unless so enunciated by the 

federal government organization or agency having statutory 

jurisdiction over any matters to which the recommendations relate. 

Emergency Beacon Corporation submitted a minority view and 

requested that it be distributed with the report. Accordingly, the 

Minority Report by Emergency Beacon Corporation is attached. 

i 
THIS PAGE INTENTIONALLY LEFT BLANK 

ii 
TAB L E o F CONTENTS 

FOREWORD ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• i 

TABLE OF CONTENTS ........................................................ STATEMENT OF WORK CONCERNING BATTERY PROBLEMS 

1.0 

2.0 

Scope ............................................................... 

Types of Batteries .....................•............................ 

2.1 Performance and Mechanical Considerations 

2.1.1 

2.1. 2 

Primary/Secondary Cells •.••••••••••••••••••••••••••••••• 

Real-time Activation Considerations ••••••••••••••••••••• 

iii 

v 

1 

1 

1 

1 

1 

2.2 New Battery Technology •••••••••••••••••••••••••••••••••••••• ~.. 2 

~"" 3.0 Potting or Encapsulation of Cells into a Battery Pack ••••••••••••••• "2--______ _ 

4.0 

5.0 

3.1 

3.2 

3.3 

Pos sib Ie Adv an tages .........••............•.••.•.......••••.... 

possible Disadvantages •••••••••••••.•••.•.••...•••••••••••••••• 

Recommenda t ions •••••••.•.••••••.•••••••••••••.••••••••••••••••• 

Placing of Batteries in Cold Storage to Extend Shelf Life 

Battery Qualifications 

5.1 

5.2 

General Requirements ••.•....••..•....••••...•••.••••••...•••••. 

Replacement Batteries, General Requirements •••••••••••••••••••• 

5.2.1 

5.2.2 

Qualification By Identicality 

Qualification By Demonstration of the MOPS .............. 

MEMBERSHIP 

APPENDIX A - CONSIDERATIONS FOR DESIGN AND MANUFACTURE OF BATTERIES FOR 

EMERGENCY LOCATOR TRANSMITTERS (ELTS) 

ATTACHMENT - MINORITY REPORT BY EMERGENCY BEACON CORP. 

2 

3 

3 

4 

4 

4 

5 

5 

6 

7 

iii 
THIS PAGE INTENTIONALLY LEFT BLANK 

iv 
SC-136 

STATEMENT OF WORK CONCERNING BATTERY PROBLEMS 

SC-136 will establish a subcommittee to review and recommend 

corrective actions on ELT battery-related problems. 

The following items related to ELT batteries have been identified as 

pertinent to this subject: 

1. Types of batteries 

Identify the types of batteries practical for use ln ELT 

applications. 

2. Potting of cells into a battery pack 

Identify advantages and adverse consequences of using this 

construction method and provide recommendations, with rationale, 

on its continuance or discontinuance. 

3. Placing of batteries in cold storage to extend shelf life 

Solicit and assimilate available data on the effectiveness of 

using cold storage for extending battery shelf life, and 

recommend the conditions under which such storage may be 

acceptable and to what extent. 

4. Replacement batteries 

Identify all technical parameters that must be met by a battery 

manufacturer to provide an approved (presume FAA TSO) 

replacement battery. If special requirements are recommended 

for inclusion in FAA ELT TSOs or Advisory Circulars, they shall 

be identified and suitable language recommended. 

The subcommittee shall prepare a separate report, keeping in mind its 

possible use for formal governmental action, such as an FAA Advisory 

Circular and/or a separate FAA TSO on batteries. 

v 
THIS PAGE INTENTIONALLY LEFT BLANK 

vi 
l.0 

2.0 

2.1 

2.1.1 

2.1. 2 

This document contains guidance and recommendations which, if 

uniformly applied as minimum requirements, provide reasonable 

assurance that the battery problems existing in the ELT 

environment will be resolved. 

Types of Batteries !/ 

Performance and Mechanical Considerations 

There are many types of batteries (cells) with various 

characteristics that are available for use in ELT 

applications depending upon the performance requirements of 

the ELT. Current drain, storage parameters (temperature and 

cycling) and physical configuration restrictions determine 

the actual choice of the basic cell. Mechanical design and 

marketing objectives also dictate system configuration. The 

original cell chemistry and mechanical design should be 

determined jointly by the ELT manufacturer and the cell 

manufacturer. Replacement batteries should demonstrate 

performance characteristics equal or superior to the original 

equipment. These batteries should be approved under the 

current certification system. 

Primary/Secondary Cells 

A number of battery types have been identified as practical 

for use in ELTs; however, they are all primary (non-rechargeable) types. The principal deficiency of the secondary 

(rechargeable) cell is its inability to provide sufficient 

capacity over the required range of temperatures that would 

be competitive with primary cells. . 

Real-Time Activation Considerations 

Some types of cells will cause a time delay for the cell to 

reach its rated output voltage. This time delay may not be 

tolerable for ELTs that use electronic latching circuits 

which must latch during the crashpulse (typically less than 

0.1 second). However, if the time delay can be tolerated 

(e.g., ELTs that use a mechanical latch) then the ELT 

manufacturer may select a cell that does have a time delay. 

!/ Appendix A provides additional information on this subject. 

1 
2 

2.2 

3.0 

3.1 

New Battery Technology 

Since the battery is a significant contributor to ELT 

performance, aviation electronic manufacturers are encouraged 

to recognize recent rapid advances in battery technology and 

consider these new technologies as power sources in their 

devices. In comparison to any of the battery systems 

presently in use, some new cells may offer improved 

characteristics, such as: 

a. Higher energy density (space and weight reductions). 

b. Broader temperature range (high and low temperature). 

c. Lower self-discharge (longer shelf life). 

Potting or Encapsulation of Cells into a Battery Pack 

There are both advantages and disadvantages associated with 

potting and encapsulation; some are listed below. It 

is essential that long-term effects of any interaction 

between the potting material/compound and cells, and other 

components of the ELT, be evaluated and fully understood to 

ensure mutual compatibility and avoid long-term destructive 

incompatibilities, such as corrosion effects. This 

understanding will provide some assurance that consideration 

of an advantage in one area or parameter will not obscure 

considerations of disadvantages in another area or parameter. 

For example, some potting compounds might provide enhanced 

resistance to fire and heat (relative to non-potted batteries) 

but may also permit a corrosive environment to be trapped 1n 

the package; or some compounds may provide many of the 

advantages listed below except that the selected compound may 

decrease the ELT's heat resistance. 

possible Advantages 

a. Can provide an inexpensive and convenient method of 

mechanically securing cells into a battery pack that is 

relatively vibration and shock resistant. 

b. Can protect the cells from physical and environmental 

damage, which may prevent shorting and corrosion as a 

result of condensation, particularly in the areas of seals 

and welded joints. 

c. Allows the battery pack to be shaped in a convenient form 

which uniquely mates with the ELT and can prevent reversed 

polarity connections. 
3.2 

3.3 

d. Discourages tampering with individual cells and/or 

unauthorized repair of battery packs. 

e. Can protect ELT electronics and other vital components by 

containing corrosive or otherwise harmful gaseous, solid 

or liquid discharges from the cells. 

f. May increase resistance to fire and heat. 

g. Can serve to effectively isolate and protect areas of 

differing electrovoltaic potentials. 

possible Disadvantages 

If proper precautions are not considered in the potting 

method or selection of material, the following problems may 

be encountered: 

a. Destructive interference may occur with the venting 

mechanism designed into the cell. 

b. A corrosive environment may be trapped 1n the package. 

c. Damaging mechanical stresses on the connections may be 

introduced. 

d. The fire and heat resistance of the ELT may be reduced. 

Recommendations 

a. Potting or encapsulating cells into a battery pack 1S 

recommended because sufficient historical data is 

available which indicates that cells can be potted 

without being detrimental to the battery's required 

performance. It can also enhance the battery's 

capability to survive and/or perform under adverse 

environmental conditions. 

b. Since there are a variety of potting methods and materials 

which can be used and since improper methods and/or 

materials may adversely affect the performance of the 

battery in an ELT, information and/or data should be 

provided to the certification authority by the ELT or 

battery manufacturer in regard to the acceptability of 

the potted or encapsulated battery. The information may 

be in the form of historical data or, in the absence of 

such information relative to the potting methods and 

material being used, test data should be provided. 

3 
4 

4.0 

5.0 

5.1 

NOTE: RTCA/DO-183, paragraph 2.1.11, "Power Supply," does 

not require tests for gas or liquid seepage, but 

the ELT or battery manufacturer is expected to 

determine if this can occur. 

c. It is also recommended that testing programs consider the 

battery ce~ls, the potting materials, the connection 

between the battery pack and the transmitter, the weight, 

strength, shock and vibration characteristics of the 

proposed total system. 

Placing of Batteries in Cold Storage to Extend Shelf Life 

From a technical standpoint there is a shelf-life benefit 

associated with the storage of batteries at controlled low 

temperatures. There are potential risks, however, which 

preclude this procedure from being a recommended practice 

for anyone but cell manufacturers. Two potential risks are: 

a. Poorly controlled low temperature conditions resulting in 

temperature cycling. 

b. Poorly controlled procedures in returning the batteries 

to ambient conditions resulting in condensation on the 

cells, terminals and insulators which could cause 

electrical shorting of the battery or cells within the 

battery package. 

Based on the risks involved, it is recommended that low 

temperature storage be used by no one other than the cell 

manufacturer. 

Battery Qualifications 

General Requirements 

The ELT manufacturer and any alternate battery replacement 

manufacturer shall provide information and/or data to the 

certification authority regarding the following: 

a. Acceptability of battery technology and potting/ 

encapsulation materials to be used for original and 

replacement batteries. This may be in the form of 

historical data or test data, as appropriate. 

b. The useful shelf life that can be expected from the 

original or replacement battery, as appropriate. This 

may include the cell self-discharge characteristics or 

per cent capacity remaining at the end of the cell's 
5.2 

5.2.1 

useful life. (Useful life is the period corresponding to 

the interim between the date of cell manufacture and the 

date that the battery must be replaced.) 

c. Assurance that future replacement batteries will 

interface with any ELT for which they were designed 

without modification to the original ELT and using no 

tooling other than that originally required for 

replacement of the battery by the ELT manufacturer. 

This shall include production tolerances and a quality 

assurance program. 

Replacement Batteries, General Requirements 

ELTs with replacement batteries shall meet RTCA/DO-183, 

"Minimum Operational Performance Standards (MOPS) for Emergency 

Locator Transmitters -- Automatic Fixed - ELT (AF), Automatic 

Portable - ELT (AP), Automatic Deployable - ELT (AD), Survival 

- ELT (S) Operating on 121.5 and 243.0 MHz." These requirements shall be met by batteries manufactured by and/or for 

the ELT manufacturer and by alternate battery sources. The 

battery package shall be replaceable only as a complete unit. 

Replacement of individual cells or a group of cells shall not 

be authorized. 

Qualification of replacement batteries shall include one of 

the following procedures: 

a. By identica1ity with the original equipment battery. 

b. By demonstration of compliance with the ELT MOPS with the 

replacement battery installed in the ELT for which it is 

designed. 

Qualification By Identicality 

If qualification is conducted on the basis of identicality 

with the original equipment battery this identica1ity shall be 

shown by either of the following methods: 

a. Conformance with the ELT manufacturer's battery 

production, process drawings and instructions. 

b. Engineering such that identica1ity is achieved in -

(1) General configuration - form, fit, and function. 

(2) Dimensional identica1ity in all aspects relating to 

construction of the battery and interface with the 

ELT. 

(3) Battery cells - identical type, voltage, capacity 

and manufacturer. 

5 
6 

5.2.2 

(4) Materials - packaging, contacts/connections, lead 

wire, solder and encapsulation. 

(5) Tolerances shall be within the ELT manufacturer's 

tolerances. 

Qualification By Demonstration of the MOPS 

If qualification is conducted on the basis of conforming to 

the MOPS that was required for the ELT's TSO authorization, 

the following procedures shall apply: 

a. Demonstrate that the replacement battery will interface 

with the unmodified ELT for which it is designed using 

no tooling other than that required for replacement of 

the original ELT battery. 

b. Unmodified ELTs mated with unused replacement batteries 

shall be subjected to and meet the requirements of the 

tests specified in DO-183, Section 2.0. 
CHAIRMAN 

S. Sokol 

SECRETARY 

R. Jago 

W. Fuchs 

MEMBERS 

L. Adams 

P. Akers 

G. Allvey 

W. Altman 

H. Alward 

J. Andres 

D. Baer 

H. Barr 

J. Bene 

L. Bessette 

K. Bierach 

R. Boer 

G. Boyle 

D. Broere 

M. Brookman 

M. Brookman 

H. Carden 

B. Chambers 

R. Climie 

J. Cline 

R. Davies 

M. de Gironville 

J. De Lorenzo 

M. DeWalt 

D. Ehrenreich 

C. Evans 

w. Fanning 

W. Felagyahazi 

J. Flavin 

J. Flood 

S. Glatzer 

J. Goodhue 

J. Goodman 

C. E. Green 

M E M B E R S HIP 

SC-I36 

ELT BATTERY SUBCOMMITTEE 

NASA Langley Research Center 

Radio Technical Commission for 

Aeronautics 

Radio Technical Commission for 

Aeronautics 

Tadiran, Inc. 

Federal Aviation Administration 

Saft America 

Dorne and Margolin, Inc. 

Union Carbide Battery 

ASD/ENACI Wright Patterson AFB 

NASA Goddard Space Flight Center 

Emergency Beacon Corporation 

NASA Langley Research Center 

Federal Aviation Administration 

Federal Aviation Administration 

NARCO Avionics, Inc. 

GTE Power Systems 

Dorne & Margolin, Inc. 

Electrochem Industries 

Saft America 

NASA Langley Research Center 

ARTEX Aircraft Supplies, Inc. 

Aeronautical Radio, Inc. 

Dayton-Granger, Inc. 

Union Carbide Corporation 

EUROCAE 

Emergency Beacon Corporation 

Federal Aviation Administration 

Tadiran, Inc. 

Southern Avionics Company 

National Business Aircraft Association 

Union Carbide Battery 

Federal Aviation Administration 

ACR Electronics, Inc. 

Emergency Beacon Corporation 

Southern Avionics Company 

Emergency Beacon Corporation 

ACR Electronics, Inc. 

7 
8 

S. Green 

G. Griffin 

D. Gutman 

D. Hall 

D. Haykin 

B. Huret 

F. Kissel 

L. Langdon 

G. Leegate 

J. Lepage 

D. Linden 

B. Loeb 

J. Longshore 

G. Lynn 

N. Marincic 

D. Marling 

T. Martin 

D. McSmith 

M. H. Merliss 

M. R. Merliss 

L. Miller 

R. Monroe 

T. Moody 

A. Murfin 

C. Naab 

A. Norwood 

T. Oneto 

C. Phipps 

G. Robinson 

D. Schacher 

D. Sieminski 

C. Sturm 

R. Taylor 

T. Telzrow 

R. Thomson 

B. Trudell 

J. Turkiewicz 

R. Va go 

J. Van Houten 

M. Vermij 

D. Wassom 

H. Waterman 

D. Wilberg 

F. Williams 

R. Wissoker 

R. Wrenn 

C. Wright 

D. Yates 

J. Young 

General Aviation Manufacturers 

Association 

NASA Goddard Space Flight Center 

NARCO Avionics, Inc. 

Robertson Research, Inc. 

NASA Goddard Space Flight Center 

Panasonic Industrial Company 

Westinghouse Electric Co. 

U. S. Department of Interior 

DME Corporation 

Canadian Marconi Company 

Duracell U. S. A. 

National Transportation Safety Board 

McDonnell Douglas Corporation 

Van Dusen Aircraft Supply Company 

Battery Engineering, Inc. 

Orion Electronics Limited 

Battelle Columbus Laboratories 

NASA Langley Research Center 

MERL, Inc. 

MERL, Inc. 

Aviation Consumer Magazine 

Aircraft Owners & pilots Association 

Cessna Aircraft Company 

Canadian Marconi Company 

Conax Corporation 

Consultant 

Aircraft Owners and pilots Association 

Aeronautical Radio, Inc. 

NASA Goddard Space Flight Center 

Tel-Instrument Electronics 

Electrochem Industries 

Federal Aviation Administration 

Beech Aircraft 

Union Carbide Corporation 

NASA Langley Research Center 

NASA Goddard Space Flight Center 

NASA Goddard Space Flight Center 

Deft Laboratories, Inc. 

Duracell U. S. A. 

Aviation Safety Bureau (Canada) 

Van Dusen Aircraft Supply Company 

Federal Aviation Administration 

Ray-o-Vac Corporation 

Servo Corporation of America 

GTE Power Systems 

Federal Aviation Administration 

Aircraft Owners & pilots Association 

Federal Communications Commission 

Federal Communications Commission 
A P PEN D I X A 

CONSIDERATIONS FOR DESIGN AND MANUFACTURE OF 

BATTERIES FOR EMERGENCY LOCATOR TRANSMITTERS (ELTS) 
THIS PAGE INTENTIONALLY LEFT BLANK 
1.0 

2.0 

2.1 

INTRODUCTION 

APPENDIX A 

Page 1 

This appendix provides reference information which may be 

applied in the design and manufacture of batteries and battery 

packs for emergency locator transmitters. The information 

provided herein was gathered in a 1983 survey of a number of 

battery cell manufacturers, domestic and foreign, under the 

auspices of RTCA Special Committee 136. This information is 

not represented as being inclusive of all significant design 

and fabrication considerations relating to ELT batteries, nor 

does this information necessarily represent a consensus 

industry opinion. 

COLD STORAGE FOR SHELF LIFE EXTENSION 

It is generally agreed that cold storage retards cell 

deterioration by impeding (1) self-discharge and (2) chemical 

reactions that tend to debilitate the cells over time. 

Industry feeling is mixed regarding the use of cold storage to 

prolong cell shelf life due to a combination of one or both of 

the following: (1) Risks associated with cold storage itself, 

(2) net economic value of cold storage costs versus shelf life 

saved. 

Risks of Cold Storage 

The risks associated with cold storage are (1) dangers 

relating to the freezing of the electrolyte, (2) short 

circuits due to moisture/condensation, (3) growth of a 

"passivation" layer in certain lithium chemistries, (4) 

mechanical expansion/contraction of the cell associated with 

cycling from high to low temperatures. 

The risk of freezing of the electrolyte was suggested by a 

lithium cell manufacturer. 

The risk associated with condensation relates to moisture 

formed internally or externally to the cell or battery pack 

while the unit is cycled between a cold and warmer 

temperature. Such moisture could result in an electrically 

conductive path or corrosion, particularly within an 

encapsulation medium. This is not thought to be a problem in 

cells that are hermetically sealed. 

Lithium-thionyl chloride systems generate a passivation layer; 

too much growth of the passivation layer is not desirable 
APPENDIX A 

Page 2 

2.2 

because it can affect the "time delay" of the ce11 in reaching 

rated voltage (this may not be an important consideration in 

some ELT systems). The worst condition for growth of the 

passivation layer in one system is around 50 degrees C. A 

temperature above or below is a better storage condition. 

Cells with excessive growth of the passivation layer can be 

recovered through partial discharge under load; such recovery 

process would result only in a loss of approximately 1% of 

capacity. 

While there exists a potential for mechanical problems 

associated with expansion/contraction under temperature 

cycles, most manufacturers felt that their products were 

essentially impervious to such problems. 

Economic Considerations of Cold Storage 

There is general consensus that the economic costs of 

maintaining cold storage for cells and batteries would not 

justify the associated shelf life extension. One manufacturer 

indicated that cold storage in the six to twelve month range 

was certainly not worth the cost. Although it is understood 

that shelf loss rates vary within chemistries among 

manufacturers, the following were offered as general rules 

that apply to specific types of chemistries. 

a. One manufacturer indicates that tests with alkaline cells 

have shown capacity retention rates of 89% after four 

years at room ambient conditions, and states that a 

reasonable shelf life under those conditions is five 

years. Shelf loss rates increase dramatically at the 

60-80% capacity level. 

b. One manufacturer of alkaline cells indicates that such 

systems can lose 7-10% of capacity per year at ambient 

room temperatures, with each increase or decrease of 10 

degrees C speeding or retarding, respectively, the shelf 

loss rate by 50%. This same manufacturer indicated that 

storage of akaline cells at 0 degrees C would result in 

an insignificant shelf loss over a six to twelve month 

period. 

c. Another alkaline cell manufacturer's published data 

indicates a 5% capacity loss per year over four years at 

ambient room temperatures. 

d. Lithium-thionyl chloride system manufacturers variously 

indicated that shelf loss rates vary from 1-2% per year 

at ambient room conditions with a total shelf life of 10 

years. Cold storage for such systems for less than a 

year would thus have marginal economic benefit. 
3.0 

3.1 

3.2 

PACKAGING/POTTING CONSIDERATIONS 

Potting/Encapsulation 

APPENDIX A 

Page 3 

It is consensus opinion that potting materials should be 

electrical insulators. In some cases, it is important that 

such materials not have high exotherm characteristics, to 

minimize heat generation during the curing process. In some 

cases, it was recommended that the potting materials either 

react chemically with cell effluent in such a way that volume 

of effluent is reduced chemically, or that such potting 

materials be permeable to hydrogen. 

It is generally agreed that the package design and any 

encapsulation materials should allow for expansion of internal 

cells. 

Most manufacturers favor full encapsulation, but one alkaline 

manufacturer specifically recommends against it in published 

literature. This manufacturer informally acknowledges that 

its cells are used regularly with full encapsulation with few 

if any detrimental effects. 

Another alkaline cell manufacturer recommends full 

encapsulation as a prevention for external leakage and cites 

no known problems with this type of packaging. 

Provisions for Venting and Out-Gassing 

Internal accommodation for venting with "free volume" which 

could be provided with open cell foams is not practical in 

some chemistries. For instance, 50-100 cc of free volume 

would be required to contain effluent gases when one existing 

type of lithium-sulfur dioxide "D" cell vented. 

Some lithium systems are designed with hermetic seals and are 

not designed to vent or out-gas under normal operating 

conditions. Some manufacturers of those systems do not see 

the need for venting or outgassing provisions. Another 

lithium cell manufacturer specifically recommends against 

external venting provisions because the effluent, if any, is 

toxic and harmful to electronic components. This 

manufacturer holds that the internal design of the cells and 

the packaging should obviate the need for external venting. 

Another Lithium cell manufacturer allows that venting 

provisions should be built in to accommodate extreme conditions 

beyond the expected operating environment. 
APPENDIX A 

Page 4 

4.0 

4.1 

4.2 

One alkaline manufacturer feels that external venting 

provisions are not necessary for alkaline battery packs. 

Lithium-thionyl chloride and alkaline cells are not fabricated 

with an internal pressure whereas lithium-sulfur dioxide 

systems do have a positive internal pressure at ambient room 

conditions. 

HAZARDS 

The types of hazards with which battery assemblers and 

operators must concern themselves in ELT batteries vary 

considerably with the chemistry involved. The following 

paragraphs contain the main areas of concern as provided by 

the cell manufacturers. 

Leakage 

Leakage can be a problem with virtually any cell chemistry, if 

the cell, by the nature of its construction or by mechanical 

deformation, is allowed to leak. Most lithium systems are 

hermetically sealed and the manufacturers discount the leakage 

problem because the integrity of the cell casing and seals are 

said to be essentially inviolate under normal operating 

conditions within the operating temperature limits established 

by the manufacturer. Most alkaline systems are crimp sealed 

and susceptible to leakage under adverse operating conditions. 

Hazards from leakage include toxic effluent which can be 

harmful to persons and equipment. 

Short Circuit Conditions 

External or internal short circuits are of particular concern 

in the lithium system in general. External shorts can be 

obviated with the use of fusing, and this is recommended by 

most manufacturers for lithium battery packs. One 

manufacturer recommends that fusing should be designed at 

double the maximum current requirement with slow-blow type 

fuses. 

One lithium cell manufacturer discourages the use of fuses 

because (1) they are not usually replaceable (2) a battery 

pack with a blown fuse could be mistaken as a "dud" or depleted 

unit and discarded as such with potential disposal-associated 

• problems. This manufacturer suggests the use of conductive 

plastics that increase in resistance as temperature rises. 

Short circuits internal to a battery pack can be obviated with 

careful attention to internal construction, isolation of lead 

wires, careful selection of the potting medium, and protection 
4.3 

4.4 

from the introduction of moisture or other conductive 

materials inside the battery pack. 

APPENDIX A 

Page 5 

In some high rate discharge cells, such as one manufacturer's 

"D" and "DD" size lithium systems, the leads will burn out 

under short circuit conditions, effectively stopping the 

short circuit condition. 

One manufacturer of high-rate lithium systems cautions that 

care should be taken to preclude the internal contact of 

cathode leads and the anode, such as could happen under 

shock/vibration -- volatile reaction could ensue. 

One alkaline cell manufacturer indicated that fusing 

circuit protection is not necessary for such systems. 

involving dead shorts at full capacity at 200 degrees 

not resulted in ignition or explosive venting. 

Polarity Reversal/Reverse Charging 

and short 

Tests 

F have 

These hazards relate generally only to lithium systems and can 

be obviated with diode protection for the battery pack and 

individual cells'. One manufacturer of lithium-thionyl 

chloride cells indicates that though diode protection is 

recommended as a fail-safe measure, its design precludes the 

problem because excess electrolyte is built into the system to 

ensure full depletion of the lithium, rendering the cell inert 

following full discharge. Low rate cells are less susceptible 

to problems in this area than high rate cells. 

Physical Abuse 

The primary concern with abuse of alkaline cells relates to 

leakage. 

Some lithium systems are sensitive to physical abuse. As 

previously indicated, shock/vibration may result in internal 

shorts in poor designs. 

Most lithium cell manufacturers put their cells through 

exhaustive mechanical testing and indicate that their designs 

are essentially impervious to physical abuse. 

One manufacturer indicates that some lithium-sulfur dioxide 

cells have shown evidence of shock sensitivity when subjected 

to significant temperature fluctuations. According to this 

respondent, the passivation layer formed on the lithium anode, 

which helps retard shelf loss, can be volatile under conditions 

where first a thick passivation layer is formed at higher 

temperatures, the cell is then held at extreme low storage 
APPENDIX A 

Page 6 

4.5 

5.0 

6.0 

temperatures (-40 degrees C) and then subsequently returned 

to ambient conditions. 

Other Hazards 

Hazards relating to venting, out-gassing, and encapsulation 

are covered in previous sections. 

All manufacturers stressed the importance of remaining within 

the manufacturer's specified operating temperature ranges. 

All manufacturers warned against the hazards of cell 

incineration. 

one manufacturer of lithium systems indicated that heat build 

up within the cell should be considered, and that battery 

packs should provide a heat sink or heat conductive path to 

obviate this type of problem. 

TESTING 

One of the questions presented in the survey related to 

testing methods to determine the efficacy of venting or 

out-gassing provisions in extreme conditions. The worst test 

conditions for venting would include an unfused short circuit 

condition at elevated temperatures, such testing being 

conducted at various capacity levels from full charge to full 

depletion. Another artificial test that would likely not be 

duplicated in real usage would be a forced overdischarge at 

elevated voltages. One lithium manufacturer indicated that 

cells should not vent within the specified operating 

temperature range, and if they vented beyond that range, the 

venting should be safely contained. Standard Department of 

Transportation tests are required. Most manufacturers go 

well beyond the requirement of these tests. 

BATTERY DESIGN AND FABRICATION HINTS 

The following hints for the design and fabrication of ELT 

batteries were gleaned from the survey. This is not intended 

to be an exhaustive listing of all considerations. 

a. Carefully consider the need for venting or out-gassing 

provisions and design to accommodate these needs. 

b. Allow for the expansion of cells within the battery pack. 

c. Consider the implications of leakage to ELT components and 

inter-cell solder connections. 
7.0 

APPENDIX A 

Page 7 

d. Potting materials, if used, should be electrical 

insulators. Consideration should be given to their 

permeability to effluent gases and the chemical reactions 

that could occur with effluent material. 

e. Use fusing and circuit protection where required. 

f. Properly isolate and insulate lead wires to preclude short 

circuits. 

g. Carefully design inter-cell and battery connections. 

Preference is to use weld tabs rather than solder straight 

to cell casings. Preferred materials for connections 

include brass, beryllium copper, or steel plated with 

nickel, silver or gold. 

h. Avoid storage of cells and batteries at high temperatures. 

i. Handle cells carefully to avoid inadvertent short circuit 

and discharge. 

j. Avoid use of heat gun and high exotherm epoxies 1n 

fabrication. 

DISPOSAL CONSIDERATIONS 

The survey included questions regarding disposal 

considerations for cells, especially those of a potentially 

toxic or volatile nature. This is considered a problem area 

by most manufacturers, particularly from a logistics point of 

view. 

As ELTs are for the most part a consumer product, the question 

of disposal logistics becomes more complex. It is possible 

that lithium battery packs in various states of depletion and 

condition will be disposed of locally by consumers, with a 

possibility of hazards that could be associated with other 

than special handling of these cells. 

Consideration should be given for battery replacement programs 

that would provide incentives for consumers to return depleted 

battery packs to manufacturers or distributors for credit 

against the purchase of replacement units. With such a 

program, there would necessarily have to be a system for 

returning depleted battery packs to the manufacturer or to 

disposal centers for processing. Battery disposal centers do 

exist at this time. 
THIS PAGE INTENTIONALLY LEFT BLANK 
MINORITY REPORT 

by 

EMERGENCY BEACON CORP. 

on 

RTCA SC-136 ELT BATTERY SUBCOMMITTEE REPORT 

ATTACHMENT 

As an active participant on SC-136 and its subcommittee on batteries, 

Emergency Beacon Corporation wishes to have a minority report included in the 

report of the SC-136 Subcommittee on Battery Problems. This minority report is 

deemed necessary because Emergency Beacon Corporation believes the majority 

report fails to adequately address the considerations in the STATEMENT OF WORK, 

paragraph 4., namely: 

"Replacement batteries: Identify all technical parameters that must be met 

by a battery manufacturer to provide an approved (presumed FAA TSO) 

replacement battery. If special requirements are recommended for 

inclusion in FAA ELT TSOs or Advisory Circulars, they shall be identified 

and suitable language recommended." 

The subject is covered in Section 5, where two methods are proposed - (1) 

Qualification by Identicality and (2) Qualification by Demonstration of the 

MOPS. The qualification by identicality section is complete and the minority 

agrees with it. Its intent is clear, i.e., that the replacement battery pack 

be identical and within the same tolerances as the original manufacturer's 

battery. Emergency Beacon Corporation, however, considers the report to be 

deficient in the area of "Qualification by Demonstration of the MOPS" because 

it does not identify all technical parameters that must be met. 

The inclusion of additional sub-paragraphs in Section 5, paragraph 5.2.2 

would, in the opinion of the minority, correct these deficiencies. The 

recommended language for each of the additional sub-paragraphs with brief 

rationale statements, follows: 

Add to 5.2.2: (c) The FAA shall furnish to the ELT manufacturer the data 

on the performance of his ELT and the applicant battery pack. The ELT 

manufacturer may inform the FAA of any areas it thinks warrant more 

detailed testing and the FAA shall determine whether such critique 1S 

valid and require such further testing, if any, as it believes is 

necessary after reviewing the ELT manufacturer's critique. 

Rationale: It is evident from readily available statistical information 

(presented to SC-136) that the major problem with replacement ELT 

batteries stems from manufacturers' attempting to do so-called "backward 

engineering" to produce a battery pack that will perform compatibly with 

an ELT. This "backward engineering" is done without knowledge of all the 

tolerances involved in the ELT and all of its eccentricities. By 

providing the ELT manufacturer with a copy of the test data of the 

proposed replacement battery pack, the ELT manufacturer can review the 

data and if some of the data is not accurate or may be in error, he can 

advise the FAA of this fact, which may place the FAA in a better position 

to closely scrutinize the tests of the applicant. We feel that the 

absence of such a provision at the present time is one of the major 
-2-

reasons for the battery problems that we have had and the 40:1 ratio of 

battery failures between those manufactured by battery-pack manufacturers 

and those manufactured by the ELT manufacturer. 

Add to 5.2.2: (d) Number of samples for qualification. A m1n1mum of two 

new fresh ELTs and ELT replacement battery packs certified by the ELT 

manufacturer will be required for testing. Where tolerances are 

involved, such as the size of the battery compartment, the batteries 

will be designed to have a tolerance to fit within the maximum difference 

between the samples. If a replacement battery manufacturer wishes larger 

tolerances he must then produce additional samples and demonstrate that 

the tolerances he has chosen fall between the limits of the smallest and 

largest of his sample population. 

Rationale: The subject of ELT battery testing is treated in the report 

only in a general way. The current report requires only that when the 

manufacturer's information is not available, the applicant must purchase 

an ELT and make tests. Since ELTs may vary in efficiency by as much as 2 

or 3 to 1, such tests using a single ELT are inadequate to qualify a 

replacement battery pack. This issue was discussed at length in various 

committee meetings and finally agreed that a minimum of two ELTs be used 

and that a tolerance be derived from those 2 ELTs and that all battery 

packs manufactured shall be required to fall within that tolerance. It 

was discussed and recognized that if a battery pack manufacturer felt 

that the tolerance was too tight he could purchase additional ELTs which 

presumably would increase that tolerance band but still assure acceptable 

performance with all ELTs in the field. 

The language proposed is simply the inclusion of a requirement agreed to 

in principle during the last subcommittee meeting. 

Add to 5.2.2: (e) Voltage and current tests. To insure proper ELT 

operation and avoid over-stressing critical components the applicant 

battery pack shall have an open circuit voltage within 5% of that of the 

manufacturer's battery pack and shall cause a current to be drawn within 

5% of that drawn by the manufacturer's battery pack. During the discharge 

test the voltage of the replacement battery pack will remain within 5% of 

the highest voltage reading and above the lowest voltage reading of the 

ELT manufacturer's battery pack. The current drawn by the ELT will be 

within 1% of the current drawn for an identical voltage when comparing the 

ELT manufacturer's battery pack to the replacement battery pack. In 

addition, the output spectrum will be within 1% of that observed with the 

ELT manufacturer's battery pack. This helps insure that there's no 

detuning or other electrical effect of the battery pack due to non-static 

conditions, such as impedance changes and proximity effects. 

Rationale: This requirement is needed to add specificity to the battery 

test and insure that the ELT is powered by the voltage it was designed for. 

Add to 5.2.2: (f) Marking. If the performance of the ELT with the 

replacement battery pack is different from the original battery pack, the 

change in performance shall be marked on the applicant's battery pack or 

expressed in a data sheet that accompanies the battery pack. This shall 
-3-

be required whether the performance is increased or decreased. 

Additionally, if limits are not known they shall be expressed as a 

qualification for the battery pack. (NOTE: If the testing is done with 

ELTs and the maximum current required ~t the starting voltage and room 

temperature is, for example, 35 milliamperes the battery shall be 

suitably marked to indicate that it may only be used on ELTs that draw 35 

milliamperes or less and the method of measuring the current or other 

parameter shall be clearly and succinctly stated in the data sheet 

accompanying the battery so that the user or installer may quickly and 

easily confirm whether the battery pack is compatible with his ELT. 

Further, if the consumer's ELT draws, for example, 55 milliamperes the 

battery pack would not be suitable for use, but if his ELT draws 35 

milliamperes or less he would be assured that the battery pack would have 

enough energy.] 

Rationale: The consumer needs some way to make an informed choice as to 

what type battery he wishes to buy. He needs to be able to look at the 

available choices and be able to weigh the price against performance. The 

consumer needs to know if the battery is not "identical" and if it may 

change the performance of the ELT. This information should be on the 

battery label or attached to the battery to permit the consumer to make an 

informed choice of a battery that would give less, equal or better 

performance for his ELT. The label will also warn the consumer if a 

particular battery pack is not compatible with his particular ELT. 

Add to 5.2.2: (g) Use of old batteries for qualification tests. One 

complete set of tests as required in RTCA/DO-l83 shall be performed with a 

battery pack made of cells that are as old as the maximum rated shelf life 

(these can usually be obtained from the cell manufacturer). 

Rationale: This would insure that there are no adverse time storage 

effects on ELT performance and prevent a repeat of the situation that 

developed with the early lithium cells which were not tested using old 

cells and developed corrosion and explosion characteristics after a 

period of several years in storage in the ELTs, resulting in numerous 

Airworthiness Directives. 

Add to 5.2.2: (h) Prominent marking labels. Prominent marking labels for 

the ELT shall be provided indicating any important parameters that have 

been changed by the new battery pack where it is significantly different 

from the old battery pack. If a description is too lengthy to be placed 

on the battery pack, a label should be conspicuously placed on the battery 

pack and the ELT stating, "Important characteristics have been changed on 

this ELT. It is mandatory to review them on the accompanying data sheet." 

Examples of conditions that would require prominent marking labels are: 

(a) A replacement battery pack that would change the flotation 

characteristics of the ELT; (b) a change in weight that could affect the 

ELT mounting locati~; (c) a change .in the operating life of the ELT, 

particularly if it is reduced; and/or (d) a change which could give false 

or inaccurate self-test readings. 

Rationale: This procedure is needed to assure the integrity of ELT 

performance with non-identical replacement batteries. 
End of Document