The current status of nickel-hydrogen (NiH2) testing ongong at NWSC, Crane In, and The Aerospace Corporation, El Segundo, Ca are described. The objective of this testing is to develop a database for NiH2 battery use in Low Earth Orbit (LEO) and support applications in Medium Altitude Orbit (MAO). Individual pressure vessel-type cells are being tested. A minimum of 200 cells (3.5 in diameter and 4.5 in diameter) are included in the test, from four U.S. vendors. As of this date (Nov. 18, 1986) approximately 60 cells have completed preliminary testing (acceptance, characterization, and environmental testing) and have gone into life cycling

Badcock, C. C.

Donley, S. W.

Felts, A. B.

Haag, R. L.

English

NASA Technical Reports Server

N88- 11028
Nickel Hydrogen Low Earth Orbit
Test Program Update and Status
Paper to be presented at the
1986 NASA/GSFC Battery Workshop
November 18-19, 1986
C. C. Badcock and S. W. Donley
The Aerospace Corporation
P. O. Box 92957
Los Angeles, CA 90009
A. B. Felts and R. L. Haag
Naval Weapons Support Center
Crane, IN 47522
_R_EDING PAGE BLANK -NOT PL_
167
https://ntrs.nasa.gov/search.jsp?R=19880001646 2020-03-20T08:51:32+00:00Z
ABSTRACT
This document describes the current status of Nickel Hydrogen (NiH 2)
testing ongoing at NWSC, Crane IN, and The Aerospace Corporation, E1 Segundo
CA. The objective of this testing is to develop a database for NiH 2 battery
use in Low Earth Orbit (LEO) and support applications in Medium Altitude Orbit
(MAO). Individual pressure vessel-type cells are being tested. A minimum of
200 cells (3 I/2 in diameter and 4 I/2 in diameter cells) are included in the
test, from four U.S. vendors. As of this date (Nov. 18, 1986) approximately
60 cells have completed preliminary testing (acceptance, characterization, and
environmental testing) and have gone into life cycling.
INTRODUCTION
In the Spring of 1984 a survey of life testing status and results for
NiH 2 cells was performed. I. Data were either available or would be available
within the next two to three years to support the use of NiH 2 batteries in
high orbits requiring up to 3000 cycles at maximum depths of discharge of up
to 80% with a high level of demonstrated reliability and confidence. Calendar
life on orbit in excess of ten years was anticipated. It was suggested that
optimum performance would be achieved when the temperature of operation was at
less than 15 deg. C and the amount of overcharge was minimized while maintain-
ing an adequate state of charge.
On the other hand, the data available to support the use of NiH 2
batteries in low earth (LEO) and mid altitude orbits (MAO) are deficient. The
extent of the data base consists of mixtures of technologies and several
generations of LEO cell designs. Cells have been tested under extreme
conditions with less regard for the limitations of these cells than is
normally applied to space-type secondary cells. However, small samples of the
most recently built cells when tested under severe conditions (90 m cycle, 80%
DOD, 1.4 C discharge, 0.8 C charge, 105% charge return ratio, 23±4 deg. C)
have consistently given 10,000 cycles before failure occurred. This suggests
that the cells have the capability to surpass the performance of present
state-of-the-art NiCd cells in LEO applications. Presently, _esign variations
among NiH 2 cells are beginning to stabilize and future changes are expected to
be incremental. Testing to establish reliability and performance appears to
be practical at this time.
168
NiH 2 cells must significantly outperform NiCd cells or they would be
disadvantageous to use because of their greater specific volume, higher
present unit cost, and the risks inherent in any new design. This increase in
performance can be in life and/or usable energy density. Present NiCd
batteries used under near-optimum conditions offer 14 - 18,000 cycles at 20 -
25% DOD and 25 - 30,000 cycles at 7 - 14% DOD depending on specific conditions
of load profile, power system requirements, and environment with high reli-
ability and confidence. NiH 2 cells must demonstrate significant increases
over these numbers if they are to be the next generation of LEO batteries.
This llfe test will demonstrate the performance capabilities of state-of-the-
art NiH 2 cells in low earth orbit, and in addition will support their use in
mid altitude orbit; and, will provide a database, when combined with other
relevant life test data and with program specific testing, that will permit an
estimate of reliability at an appropriate confidence level.
Objectives and Goals
The NiH 2 cell life test has the following objectlves2:
I •
o
3.
4.
5.
Demonstrate NIH 2 performance in LEO applications and support use in
MAO at levels superior to current NiCd capabilities.
Develop a statistically significant NIH 2 battery cell database.
Disseminate the test data and results in a timely fashion.
Demonstrate NiH 2 cell performance in pulse applications.
Demonstrate that the Manufacturing Technology Program (MANTECH)
cells are capable of performing in high orbit as well as LEO.
It is the intent to test cells from all viable vendors in sufficient
numbers to provide a comparison and to establish a statistically significant
database with a sufficiently high confidence level. A minimum of 155 3.5 in
diameter and 45 4.5 in diameter cells are included in the test plan. Addi-
tional cells will be added as the need is demonstrated• Approximately equal
numbers of cells from four U.S. vendors (GEBBD, Eagle Picher, Yardney, and
HAC) are to be tested in so far as schedule and funding permit.
The goals of these tests are to demonstrate at least 30,000 cycles at 40%
DOD and at least 20,000 cycles at 60% DOD in LEO and at least 5000 cycles at
169
80% DOD in MAO or high orbit. The 40% DOD cycle goal is greater than present
NiCd cells can expect to achieve at three years of planned life. A small
number of cells (5 from each vendor) will be tested at 25% DOD to provide
correlation with present NiCd testing and life data bases. It must be empha-
sized that cells could fail to reach desired goals, e.g. 60% DOD and 5 years,
and still perform significantly better than present state-of-the-art NiCd
cells.
A second goal is to establish a minimum reliability of 90% with a con-
fidence level of at least 80% for the goals stated above. This goal requires
an additional year of testing beyond the goal periods, if one assumes the
improbable condition that none of the groups of ten cells can be statistically
combined.
Reports are issued when significant milestones are reached and at regular
periods. Each major milestone, e.g. completion of acceptance testing, results
in a brief report. The progress of the test shall be reported in an "Annual
Report of Cycle Life Testing" from NWSC Crane and will, in additlon, be
summarized at least once a year and presented in an appropriate forum (of
which this is the second). The detailed data will remain available after
completion of the test for access by qualified organizations.
Test Plan
The test plan consists of acceptance and pre-life testing (including
environmental testing), characterization testing, life testing, and failure
and end-of-test analyses. Cell manufacturing specifications, testing pro-
cedures, and failure analysis procedure have been fully documented, except for
end-of-test analysis which is in preparation.
All the packs in the test will be 10-cell packs except for those (LEO 25%
DOD and some 4.5 in. packs) that are meant mainly to correlate with other data
bases. The standard sample size of 10 was chosen by a method based on the
two-parameter Weibull failure distribution function as a compromise between
the high cost of a large sample size and the statistical uncertainties of a
small sample size.
170
Acceptance Testing: Acceptance testing is conducted at NWSC. All cells
of the same type and from the same vendor are tested in a single series string
whenever practicable. The following tests are performed on all cells:
I •
2.
3.
5.
6.
7.
Visual inspection, weight, and dimensions (diameter and length).
Indicator leak test (at beginning and end of testing).
Conditioning capacity (I0°C, repeat until two cycles agree within 2%
in capacity).
Standard Capacities at -5 ° , 10 ° , and 20°C.
Impedance at 50% state of charge and 20°C.
Overcharge voltage and pressure stability (when available) at O°C.
Capacity loss upon charged stand at I0°C for 72 hours.
The ampere-hour and watt-hour capacities of the cells are reported to 1.20,
1.15, 1.10, 1.05, 1.00, and 0.5 V. at the standard discharge rate (a C rate is
used to correlate with the rates used in testing). All temperatures refer to
the midpoint along the cell cylinder on the thermal flange.
A 20% sample of the cells of each type (at least two cells) and from each
vendor are subjected to random vibration testing at levels 6 dB higher than
the highest level anticipated in any application. The cells that are vibrated
will be distributed throughout the test packs to determine any long-term
effects of vibration.
Characterization Testing: These tests are performed to determine the
required charge characteristics. A group of 5 are cells of each type and from
each vendor are tested to determine charge efficiencies at selected rates and
temperatures. These data along with acceptance data are used to initiate
charge control for life testing.
Life Testing: Life testing will be performed using a nominal 90 minute
orbit with a 30 min. eclipse period and a 60 rain. sun period• Testing will be
performed at -5 ° and I0°C with the latter temperature being baseline. In a
corporate program-oriented test at Martin-Marietta Aerospace, 20oC is being
used for a group of cells. 3 We choose not to duplicate this condition. The
charge control method is ampere-hour integration (recharge fraction
control). This method is flexible and particularly easy to integrate into a
digital control system. In the LEO testing, control is accomplished by
171
changing the charge returned under a fixed depth of discharge until the
following parameters are minimized:
I •
2.
3.
The decrease in the end of discharge voltage.
The increase in the end of charge voltage (high rate and trickle).
The recharge fraction (both watt-hour and ampere-hour).
A limit of a 112% charge return is established to permit the setting of
charge rate capability (charge returns of this size are not anticipated during
testing.) The charge sequence for LEO will be to return 100% of the charge at
the required rate followed by C/5 charging for the remember of the charge
period. The high charge rate is adjusted to set the charge control
parameters. A similar approach will be used in MAO but the high charge rate
and the final charge rates will be lower. Trickle charge, which is used only
in emergencies, will be at C/80 or lower.
Reconditioning is not planned for the cells in LEO testing. MAO testing
may require reconditioning to maintain adequate efficiency. No capacity
discharges will be performed.
Failure is defined as a voltage of less than 0.50 V at the end of the
prescribed discharge or a voltage greater than 1.75 V during any portion of
the charge. Data for other end-of-useful-life criteria will be available.
Upon being declared a failure, the affected cell will be removed from the test
pack and subjected to a repeat of at least part of the acceptance test within
180 days of failure. The cell will then be dispositioned for further failure
analysis.
The schedule given on Figure I shows the proposed plan. It is hoped that
the test will continue until the majority of the cells in each pack have
failed.
Special Testing: The general test will employ continuous constant dis-
charges. However, the applications requiring pulsed high rate discharge
within the envelope of the planned DODs are sufficiently prevalent to make the
correlation of such results with the general llfe test important. A small
group of cells will be placed on llfe test in a pulse discharge regime at
maximum rates of approximately 5C. Cells will be acceptance tested at the
172
testing organization and sent to The Aerospace Corporation Battery Evaluation
Laboratory for the special testing.
RESULTS AND STATUS
The full test matrix of cells expected to be tested is shown in Table
I. The total number of cells of all types and from all vendors is 275, of
which 210 are 3.5 in diameter cells and 65 are 4.5 in diameter. Numbers and
types of cells currently on hand or committed are shown in Table 2. Some
cells manufactured in or prior to 1985 were found initially to have
insufficient capacity. These have been subjected to a LEO cycling regime in
order to increase their capacities to the mlnim_ level required, namely 50 Ah
for 3.5 in diameter cells. In all cases the capacities of affected cells have
been recovered in this way, although requiring more than 400 LEO cycles in
some cases. Newly manufactured cells have not exhibited this characteristic.
It is estimated that by the date of delivery of this paper 57 3.5 in
diameter cells will be undergoing life cycling. The remainder of the 3.5 in
cells on hand at this time, numbering 46 cells, will be undergoing pre-life
testing for a total of 103 3.5 in diameter cells. Also, by this date 21 4.5
in diameter cells will have been received and will be in preparation for
testing. Additionally, 45-3.5 in diameter cells, and 20-4.5 in diameter cells
are on order and are to be received during FY 1987, so that by the end of FY
1987 189 cells should be undergoing testing in both LEO and MAO regimes.
We expect to have completed acceptance, characterization, and
environmental testing on all 103 cells that are on hand at Crane by the end of
January 1987. These cells will enter llfe testing as soon as pack assignments
can be made but no later than the completion of all pre-llfe testing. Twenty-
one high rate 4.5 inch diameter cells are expected in the last quarter of
1986. These will enter prelife testing as soon as the equipment is available
(January 1987).
173
REFERENCES
I • C. C. Badcock and M. J. Milden, Nickel Hydrosen Battery Cell Testing Data
Base: An Industry and Government Survey, Space Division/Air Force
Systems Command, No. SD-TR-85-88, Dec. 31, 1985.
1 C. C. Badcock, Nickel-Hydrogen Low Earth Orbit Test Prosram, paper pre-
sented the 1985 NASA/GSFC Battery Workshop, Greenbelt, MD, Nov. 29, 1985.
• J. K. McDermott, Low-Earth-Orbit TestinB of Nickel-Hydrogen Cells, paper
presented at the 21st Intersociety Energy Conversion Engineering
Conference, Aug. 25-29,1986.
174
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Nickel hydrogen low Earth orbit test program update and status

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