Brianne T. Scheidegger

Glenn Research Center, Cleveland, Ohio

Performance Assessment of Baseline Cells for the

High Effi ciency Space Power Systems Project

NASA/TM—2012-217285

January 2012
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Brianne T. Scheidegger

Glenn Research Center, Cleveland, Ohio

Performance Assessment of Baseline Cells for the

High Effi ciency Space Power Systems Project

NASA/TM—2012-217285

January 2012

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Available from

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7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

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Alexandria, VA 22312

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Space Administration.

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2012-217285 1 

Performance Assessment of Baseline Cells for the 

High Efficiency Space Power Systems Project 

Brianne T. Scheidegger 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

The Enabling Technology Development and Demonstration (ETDD) Program High Efficiency Space Power 

Systems (HESPS) Project, formerly the Exploration Technology Development Program (ETDP) Energy Storage 

Project is tasked with developing advanced lithium-ion cells for future NASA Exploration missions (Ref. 1). Under 

this project, components under development via various in-house and contracted efforts are delivered to Saft America 

for scale-up and integration into cells. Progress toward meeting project goals will be measured by comparing the 

performance to these cells with cells of a similar format with Saft’s state-of-the-art aerospace chemistry. This report 

discusses the results of testing performed on the first set of baseline cells delivered by Saft to the NASA Glenn 

Research Center. This build is a cylindrical “DD” geometry with a 10 Ah nameplate capacity. Testing is being 

performed to establish baseline cell performance at conditions relevant to ETDD HESPS Battery Key Performance 

Parameter (KPP) goals including various temperatures, rates, and cycle life conditions. 

Data obtained from these cells will serve as a performance baseline for future cell builds containing optimized ETDD 

HESPS-developed materials. A test plan for these cells was developed to measure cell performance against the high 

energy cell KPP goals. The goal for cell-level specific energy of the high energy technology is 180 Wh/kg at a C/10 

discharge rate and 0 °C. The cells should operate for at least 2000 cycles at 100 percent DOD with 80 percent capacity 

retention. Baseline DD cells delivered 152 Wh/kg at 20 °C. This number decreased to 143.9 Wh/kg with a 0 °C 

discharge. This report provides performance data and summarizes results of the testing performed on the DD cells. 

Introduction 

To address the need for improved energy storage devices with high specific energy, long cycle life, and improved 

safety for future NASA missions, the ETDD High Efficiency Space Power Systems Project (HESPS) is developing 

components for integration into high energy lithium-ion cells. This work began under the Exploration Technology 

Development Program Energy Storage Project. The Key Performance Parameters (KPP) for high specific energy cells 

include specific energy of 180 Wh/kg at 0 °C and a C/10 rate, 80 percent capacity retention after 2000 cycles at 

100 percent depth-of-discharge (DOD), and safe and reliable performance. The HESPS Battery KPP values are 

provided in Table 1. 

To support this effort, NASA teamed up with an industrial partner, Saft America, to scale-up materials and build 

evaluation and flight cells. Materials developed under multiple NASA Research Announcement contracts were 

delivered to the NASA Glenn Research Center (GRC), Johnson Space Center (JSC), and Jet Propulsion Laboratory 

(JPL) for performance screening. Once the materials were screened and met certain minimum performance 

requirements, the materials were passed on to Saft for scale-up and associated activities (Ref. 2). 

In October 2009, Saft delivered a build of cylindrical DD cells containing their baseline electrode chemistry to the 

NASA GRC. This cell was chosen because it is a flight heritage design and easily manufactured at Saft. The cell 

assessment would serve as a baseline for comparison against future cell deliveries. 

The NASA ETDD HESPS project team created the test plan to assess the performance of candidate cells against 

the KPP goals. The cells were subjected to temperature, rate, and cycling conditions relevant to the ETDD high energy 

goals. This report summarizes the results of performance characterization of Saft’s DD baseline cells. 
NASA/TM—2012-217285 2 

TABLE 1.—KEY PERFORMANCE PARAMETERS 

Customer Need Performance 

Parameter

State-of-the-Art Current Value Threshold Value Goal

Safe, reliable 

operation

No fire or flame Instrumentation/controllers used to prevent 

unsafe conditions. 

There is no nonflammable electrolyte in 

SOA

Preliminary results 

indicate a small reduction 

in performance using 

safer electrolytes and 

cathode coatings

Tolerant to electrical and 

thermal abuse such as 

over-temperature, overcharge, reversal, and 

short circuits with no fire 

or thermal runaway****

Tolerant to electrical and 

thermal abuse such as 

over-temperature, overcharge, reversal, and 

short circuits with no fire 

or thermal runaway****

Specific energy

Lander:

150 – 210 Wh/kg

10 cycles

Rover:

160-200 Wh/kg

2000 cycles

EVA:

270Wh/kg

100 cycles

Battery-level

specific energy*

[Wh/kg]

90 Wh/kg at C/10 & 30 C

83 Wh/kg at C/10 & 0 C

(MER rovers)

160 at C/10 & 30 C (HE)

170 at C/10 & 30 C (UHE)

80 Wh/kg at C/10 & 0 C

(predicted)

135 Wh/kg at C/10 & 0 C 

“High-Energy”**

150 Wh/kg at C/10 & 0 C 

“Ultra-High Energy”***

150 Wh/kg at C/10 & 0 C 

“High-Energy”

220 Wh/kg at C/10 & 0 C 

“Ultra-High Energy”

Cell-level specific 

energy

[Wh/kg]

130 Wh/kg at C/10 & 30 C

118 Wh/kg at C/10 & 0 C

199 at C/10 & 23oC (HE)

213 at C/10 & 23oC (UHE)

100 Wh/kg at C/10 & 0oC

(predicted)

165 Wh/kg at C/10 & 0 C 

“High-Energy”

180 Wh/kg at C/10 & 0 C 

“Ultra-High Energy”

180 Wh/kg at C/10 & 0 C 

“High-Energy”

260 Wh/kg at C/10 & 0 C 

“Ultra-High Energy”

Cathode-level

specific capacity

[mAh/g]

180 mAh/g 252 mAh/g at C/10 & 25oC

190 mAh/g at C/10 & 0oC

260 mAh/g at C/10 & 0 C 280 mAh/g at C/10 & 0 C 

Anode-level

specific capacity

[mAh/g]

280 mAh/g (MCMB) 330 @ C/10 & 0oC (HE)

1200 mAh/g @ C/10 & 0oC 

for 10 cycles (UHE)

600 mAh/g at C/10 & 0 C 

“Ultra-High Energy”

1000 mAh/g at C/10 0 C

“Ultra-High Energy”

Energy density

Lander: 311 Wh/l

Rover: TBD

EVA: 400 Wh/l

Battery-level

energy density

250 Wh/l n/a 270 Wh/l “High-Energy”

360 Wh/l “Ultra-High”

320 Wh/l “High-Energy”

420 Wh/l “Ultra-High”

Cell-level energy 

density

320 Wh/l n/a 385 Wh/l “High-Energy”

460 Wh/l “Ultra-High”

390 Wh/l “High-Energy”

530 Wh/l “Ultra-High”

Operating 

environment

0oC to 30oC, Vacuum

Operating 

Temperature

-20oC to +40oC 0oC to +30oC 0oC to 30oC 0oC to 30oC

Key Performance Parameters for Battery Technology Development

Revised 9/20/10

Assumes prismatic cell packaging for threshold values. Goal values include lightweight battery packaging.

* Battery values are assumed at 100% DOD, discharged at C/10 to 3.0 volts/cell, and at 00C operating conditions

** ”High-Energy” = mixed metal oxide cathode with graphite anode

*** “Ultra-High Energy” = mixed metal oxide cathode with Silicon composite anode

**** Over-temperature up to 1100C; reversal 150% excess discharge @ 1C; pass external and simulated internal 

short tests; overcharge 100% @ 1C for Goal and 80% @ C/5 for Threshold Value.
NASA/TM—2012-217285 3 

Test Articles 

The 10 Ah capacity DD cell configuration was chosen for the screening process due to its flight heritage design 

and ease of manufacturing by Saft. Ten DD cells were delivered to the NASA GRC in October 2009. The cells are 

spiral-wound cylindrical cells with a stainless steel container. Cells contain a burst disc at the negative end and came 

with tabs welded at each terminal. Table 2 lists pertinent measurements taken during the incoming physical and 

electrical inspection. Cells contain Saft’s baseline chemistry and “space” organic electrolyte. The baseline chemistry is 

a nickel alloy-based cathode and graphite-based anode. 

With the above components, each cell should nominally deliver 10 Ah of capacity, or 140 Wh/kg based on a 

nominal discharge voltage of 3.5 V and cell mass of 0.25 kg. The cell-level specific energy during testing was 

calculated using the individual cell masses listed in Table 2, which included welded tabs, and capacity taken as the 

average Ah delivered for all cells. Figure 1 depicts a DD cell with tabs and an attached thermocouple. 

TABLE 2.—SAFT DD CELL INSPECTION DATA 

Figure 1.—DD design. 

Inspection Date: Oct 16, 2009 BATTERY CELL PHYSICAL AND ELECTRICAL

Inspected by: BTS & DEY

MANUFACTURER: Saft PART/LOT # 1054

DATE OF MANUFACTURE: DATE RCV'D: 6-Oct-09

Serial Weight Dimensions (cm)

Number (grams)

Bare Cell Height w' OCV

with tabs Diameter Height Terminals Neg. to Pos. Pos. to Case

21 251.2 3.35 12.38 12.53 3.610 3.610

30 250.2 3.34 12.35 12.55 3.602 3.602

32 251.2 3.36 12.32 12.46 3.602 3.602

33 249.4 3.34 12.32 12.51 3.601 3.601

37 249.3 3.36 12.33 12.42 3.603 3.603

39 249.9 3.33 12.26 12.43 3.603 3.603

41 250.3 3.34 12.36 12.51 3.604 3.604

43 250.1 3.35 12.31 12.44 3.603 3.603

48 250.4 3.34 12.29 12.44 3.602 3.602

49 251.7 3.34 12.37 12.45 3.603 3.603

INSPECTION DATA

Voltage 
NASA/TM—2012-217285 4 

Experimental 

The test program initiated for developmental and commercial lithium-ion cells includes characterization and cycle 

life testing. Test plans were developed to evaluate performance against KPP metrics. 

Characterization tests were performed on all ten cells to assess their performance at several temperature and 

discharge rate conditions. Table 3 outlines the test conditions the cells were subjected to during characterization. Cycle 

life testing is also currently in progress. 

TABLE 3.—CELL TESTING OUTLINE 

Test (in order) Charge ratea Charge 

temperature, 

°C 

Discharge ratea Discharge temperature, 

°C 

Conditioning C/5 20 C/2 20 

Temperature 

characterization 

C/5 20 C/10 30, 20, 10, 0 

20 °C rate 

characterization 

C/5 20 C/10, C/5, C/2 20 

20 °C/0 °C rate 

characterization 

C/5 20 C/10, C/5, C/2 0 

0 °C rate 

characterization 

C/5 0 C/10, C/5, C/2 0 

Cycle Life (bulk w/out 

diagnostics) 

C/5 20 9 cycles C/10, 1 cycle C/2 

repeated 

20 and 0 in parallel 

a

The cells were cycled between voltage limits of 3.00 and 4.10 V. KPP goals for cell-level specific energy are stated at 

100 percent Depth of Discharge (DOD) to 3.00 V and data is presented to that cutoff voltage. 

Cell Conditioning 

Conditioning cycles were performed to ensure the cells had consistent, stable performance and to provide an actual 

capacity for each cell. Conditioning consisted of a minimum of five cycles at 20 °C. Cells were charged at constant 

current (CC) at C/5 to 4.10 V with a “C” of 10 Ah followed by a constant voltage (CV) charge until the current tapered 

to C/50. Following a 1-hr open circuit rest the cells were then discharged at a C/2 rate to 3.00 V. This cycle was 

repeated until the cells reached at least five cycles and the change in capacity between cycles was less than ±1 percent. 

Values for charge and discharge current of all subsequent testing used the average of the cells’ actual capacities 

determined from this conditioning as “C”. 

Temperature Characterization 

Temperature characterization was performed to evaluate capacity as a function of discharge temperature. The cells 

were charged at room temperature (20 °C) for all cycles and discharged at temperatures of 0, 10, 20, and 30 °C. Cells 

were allowed to soak for 2 hr between charge and discharge to allow for temperature equilibration. The cells were 

charged at a CC C/5 rate to 4.10 V followed by a CV taper to C/50. Discharges were performed at a CC C/10 rate to 

3.00 V at all temperatures. 

Rate Characterization 

Rate characterization was performed to determine the performance of the cells when discharged at different rates at 

room temperature and 0 °C conditions. The cells were charged at a CC C/5 rate to 4.10 V and CV taper to C/50 for all 

tests. Discharge was performed at C/10, C/5, and C/2 discharge rates for three cycles each. This rate characterization was 

performed at room temperature for both charge and discharge (“20 °C”), a 20 °C charge followed by 0 °C discharge 

(“20/0 °C”), and 0 °C for both charge and discharge (“0 °C”). This allowed an evaluation of the effect of a 0 °C charge on 

the performance of the cell compared to 20 °C charging conditions. Some of the tests from “Temperature 

Characterization” were repeated with this method, including the C/10 rate discharge at 20 °C and 20/0 °C. 
NASA/TM—2012-217285 5 

For tests with alternating temperature conditions between charge and discharge, such as the 20/0 °C rate 

characterization and temperature characterizations, a 2-hr soak period was used to allow for stabilization of the cell 

core temperature. All other tests included 1-hr rests following charge and discharge to allow the cells to equilibrate 

within the environmental chamber. 

Cycle Life Testing 

The cycle life test regime assesses the KPP high energy requirement of 2000 cycles at 100 percent DOD with at 

least 80 percent capacity retention. The test regime includes periodic diagnostic cycles to assess the current state of the 

cell every 200 cycles. The diagnostics are performed at 0, 20, and 30 °C. The cells are cycled with a CC C/5 charge 

rate to 4.10 V followed by a CV taper to C/100 and discharged at C/10 except for a C/2 discharge every tenth cycle, to 

a 3.00 V cutoff. This step is meant to periodically gauge the C/2 performance. 

Cycle life testing is performed at two different temperature conditions. Five cells are held at 20 °C (excluding 

diagnostics every 200 cycles) and the remaining cells are charged at 20 °C and discharged at 0 °C. Other than the 

temperature difference and temperature dwell times, the test procedures remain identical for all cells. 

Test Equipment 

All cells are housed in environmental chambers for temperature control with a nitrogen purge to provide an inert 

environment. An Arbin BT2000 Battery Testing System is used to provide current control during testing. The MITS 

Pro companion software is used to control the charge and discharge profiles, monitor safety limits, and collect data. 

The Arbin’s auxiliary temperature channels are used to monitor the cell and ambient temperatures during testing.

Results and Discussion 

Cell Conditioning 

The cells completed five conditioning cycles, although the capacity stabilized to less than ±1 percent in the second 

cycle. “C” was determined by averaging the discharge capacity of all cells in the fifth cycle and determined to be 

10.0 Ah. The capacity amongst cells was uniform, varying by no more than ±1 percent of the average “C.” The cells 

delivered 10.3 Ah during similar testing at Saft; however the tests were performed at 30 °C as opposed to 20 °C at 

NASA GRC. Data shows a capacity increase of 2.1 percent when the temperature is increased from 20 to 30 °C, which 

may partially explain the differences in these data. 

Temperature Characterization 

Temperature characterization provided baseline performance data for the cells at a C/10 discharge rate at several 

temperature conditions. Figure 2 shows the discharge curves for each DD cell at 20 °C only, illustrating that there is 

very little variability amongst the ten cells. The variability can also be seen in data from Table 4, which lists the 

specific energy delivered for each cell at 20 °C and also provides the 0, 10, and 30 °C specific energies as both values 

and percentages of the 20 °C performance. The cells delivered 157.2 Wh/kg at 20 °C. The cells showed a slight 

improvement at 30 °C, delivering 160.6 Wh/kg. Cells delivered 150.4 and 143.1 Wh/kg at 10 and 0 °C, respectively. 

Figure 3 shows the C/10 performance for a representative cell over the 0 to 30 °C temperature range. Baseline 

performance was taken at 20 °C at which point the cells delivered 157.2 Wh/kg. The impact of discharge temperature 

on the specific energy can be easily seen in the plot. Specific energy decreased by 9.0 percent when the cells were 

discharged at 0 °C. Discharge temperature did not affect the coulombic efficiency, but the energy efficiency decreased 

with decreasing temperature, falling from 97.3 percent at 30 °C to 96.8 percent at 0 °C. Table 5 lists the coulombic and 

energy efficiency of each cell. 
NASA/TM—2012-217285 6 

Figure 2.—The 20 C C/10 discharge voltage versus specific energy for ten DD cells. 

TABLE 4.—THE C/10 TEMPERATURE CHARACTERIZATION DATA FOR DD CELLS 

 

3

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3.4

3.6

3.8

4

4.2

0 20 40 60 80 100 120 140 160 180

CellVoltage

V

Specific Energy Wh/kg

21 30

32 33

37 39

41 43

48 49

Cell

20°C

Wh/kg Wh/kg

% of 20°C

energy Wh/kg

% of 20°C

energy Wh/kg

% of 20°C

energy

21 156.7 160.1 102.2% 149.9 95.7% 142.8 91.1%

30 157.3 160.6 102.1% 150.4 95.6% 143.0 91.0%

32 156.7 159.9 102.1% 149.8 95.6% 142.5 91.0%

33 157.6 161.0 102.1% 150.7 95.6% 143.3 90.9%

37 157.0 160.7 102.3% 150.3 95.8% 143.1 91.2%

39 157.7 161.1 102.2% 150.9 95.7% 143.6 91.1%

41 156.6 160.3 102.3% 149.8 95.7% 142.6 91.1%

43 156.8 160.4 102.3% 150.0 95.7% 142.8 91.1%

48 157.5 160.8 102.1% 150.7 95.7% 143.4 91.1%

49 158.2 161.0 101.8% 151.3 95.6% 144.0 91.0%

Average 157.2 160.6 102.1% 150.4 95.7% 143.1 91.0%

Coeff of Var 0.34% 0.25% 0.16% 0.33% 0.04% 0.33% 0.09%

30°C 10°C 0°C
NASA/TM—2012-217285 7 

Figure 3.—The C/10 temperature characterization for DD cell 32. 

TABLE 5.—EFFICIENCY DATA FOR TEMPERATURE 

CHARACTERIZATION AT C/10 

Rate Characterization 

Next, cells were assessed for 20 °C rate performance. Similar to results from temperature characterization at C/10, 

the cells delivered 157.2 Wh/kg (10.82 Ah) at a C/10 rate. All showed decreasing energy with increasing discharge 

rate. The tests were run from the lowest (C/10) discharge rate to the highest (C/2) with the C/10 discharge repeated 

after the higher rate characterization cycles. There was no observable difference in specific energy after the 12 rate 

capability cycles and the coulombic efficiency remained 99.9 percent at all rates. The cells experienced a 9 percent 

reduction in capacity at a C/2 discharge rate when compared to C/10, delivering 143.1 Wh/kg at C/2. Table 6 and 

Figure 4 show the performance of the cells at various rates at 20 °C and each discharge curve in Figure 4 is an average 

of all ten cells on test. Specific energy values are presented as percentages of the C/10 specific energy. Additionally, 

little variability among cell performance was observed. 

Rate characterization at lower temperatures was performed to determine the ability of the cells to discharge at 

lower temperatures. Cells were charged and discharged under the 20/0 °C rate conditions. These tests were meant to 

simulate actual temperature conditions a cell may experience while in use by any of the ETDD’s customers where 

charging would occur in a controlled environment and batteries would be exposed to ambient conditions during 

discharge. 

3

3.2

3.4

3.6

3.8

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0 20 40 60 80 100 120 140 160 180

CellVoltage

V

Specific Energy Wh/kg

30°C discharge

20°C discharge

10°C discharge

0°C discharge

Temperature

Coulombic

Efficiency

Energy

Efficiency

30°C 99.8% 97.3%

20°C 99.9% 97.2%

10°C 99.8% 97.1%

0°C 99.8% 96.8%
NASA/TM—2012-217285 8 

TABLE 6.—DD RATE CHARACTERIZATION AT 20 °C 

Figure 4.—The 20 °C DD rate characterization discharge curves. 

 

Cell

C/10

Wh/kg

C/5 as %

of C/10

Wh/kg

C/2 as %

of C/10

Wh/kg

final C/10

as % of

C/10 Wh/kg

21 156.8 96.7% 91.0% 99.8%

30 157.2 96.7% 91.0% 99.8%

32 156.7 96.7% 90.9% 99.8%

33 157.7 96.7% 91.1% 99.8%

37 157.1 96.7% 91.0% 99.8%

39 157.7 96.7% 91.2% 99.8%

41 156.6 96.7% 91.1% 99.8%

43 156.8 96.7% 91.0% 99.8%

48 157.5 96.8% 91.2% 99.8%

49 158.2 96.7% 90.9% 99.8%

Avg 157.2 96.7% 91.0% 99.8%

Coeff of Var 0.3% 0.0% 0.1% 0.0%

3

3.2

3.4

3.6

3.8

4

4.2

0 20 40 60 80 100 120 140 160 180

CellVoltage

V

Specific Energy Wh/kg

C/10

C/5

C/2

final C/10
NASA/TM—2012-217285 9 

Cells were tested under these conditions for comparison with 20 °C performance. The cells delivered an average of 

143.9 Wh/kg at a C/10 rate and 0 °C; this is approximately 91.6 percent of the 20 °C performance. The cells delivered 

128.8 Wh/kg at C/2, 89.5 percent of the C/10 energy under these temperature conditions. The performance hit between 

C/10 and C/2 for these conditions is slightly worse than at 20 °C (91.0 percent from C/10 to C/2). Figure 5 and Table 7 

illustrate the data collected for 20/0 °C testing. The average voltage during discharge was comparable to 20 °C at C/10 

and C/5 discharge rates; however the average voltage for the C/2 discharge rate was roughly 20 mV lower for the 

20/0 °C condition. The energy efficiency at every discharge rate was lower for this testing than 20 °C, and the energy 

efficiency experienced a larger decline between C/10 and C/2. The general observation is the 0 °C discharge has a 

greater effect on the cell performance as discharge rate is increased. 

Figure 5.—The 20/0 °C rate characterization. 

TABLE 7.—THE 0 °C DD RATE CHARACTERIZATION 

3

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3.6

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4

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0 20 40 60 80 100 120 140 160 180

CellVoltage

V

Specific Energy Wh/kg

C/10

C/5

C/2

Cell

C/10

Wh/kg

C/5 as %

of C/10

Wh/kg

C/2 as %

of C/10

Wh/kg

21 143.5 95.6% 89.7%

30 143.8 95.5% 89.5%

32 143.3 95.5% 89.4%

33 144.3 95.5% 89.6%

37 144.0 95.5% 89.4%

39 144.3 95.6% 89.7%

41 143.5 95.5% 89.4%

43 143.7 95.5% 89.4%

48 144.3 95.6% 89.5%

49 144.8 95.5% 89.2%

Avg 143.9 95.5% 89.5%

Coeff of Var 0.3% 0.1% 0.2%
NASA/TM—2012-217285 10 

Figure 6.—DD rate characterization at 0 °C. 

Rate characterization was also performed while both charging and discharging the cells at 0 °C. Performance at 

C/10 was similar to results obtained with 20/0 °C characterization. An average of 141.3 Wh/kg (9.68 Ah), or 

89.9 percent of the 20 °C specific energy, was observed and the cells did not experience a severe drop in performance 

at higher rates. A capacity drop of 10 percent from C/10 to C/2, similar to the drop at 20 °C, was also seen at this 

temperature as seen in Figure 6. Note that the discharge curves in Figure 6 corresponding to “C/10” and “final C/10” 

discharge rates overlap, resulting in the original “C/10” curve disappearing in the plot. In comparison, the average 

voltage during charge for 0 and 20/0 °C testing was 3.74 V, versus 3.70 V for 20 °C testing. The 0 and 20/0 °C tests 

reached the 4.10 V charge cutoff more quickly than the testing at 20 °C, and accumulated less capacity during charge 

as a result. These tests also resulted in the most significant voltage recovery during the hour-long open circuit rest 

following discharge. The voltage recovered from 3.00 V at the end of discharge and ranged from 3.34 to 3.42 V at the 

beginning of the following charge. Voltage recovery for 20 °C tests ranged from 3.23 to 3.29 V after discharging to 

3.00 V. These cells then had a larger charge voltage window and accumulated more capacity during charge than tests 

incorporating the 0 °C discharge. Figure 7 shows the voltage profile of a representative cell during charge at each 

condition. While the charge profiles appear similar at the 0 and 20/0 °C conditions, the data also leads to the 

conclusion that the act of performing discharging at 0 °C had a more significant effect on the performance of the cell 

than the charge condition, whether it was 0 or 20 °C. 

To make an overall performance comparison, Figure 8 compares the C/10 performance during rate characterization 

of the cells at each of the three temperature condition described above and shows little difference in the results of tests 

performed at low temperatures. 

 

3

3.2

3.4

3.6

3.8

4

4.2

0 20 40 60 80 100 120 140 160 180

CellVoltage

V

Specific Energy Wh/kg

C/10

C/5

C/2

final C/10
NASA/TM—2012-217285 11 

Figure 7.—Cell 33 C/5 charge profiles. 

Figure 8.—DD Cells at C/10 in rate characterization. 

3

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3.4

3.6

3.8

4

4.2

0 2 4 6 8 10 12

CellVoltage

V

Charge Capacity Ah

20°C

20/0°C

0°C

3

3.2

3.4

3.6

3.8

4

4.2

0 20 40 60 80 100 120 140 160 180

CellVoltage

V

Specific Energy Wh/kg

20°C

20/0°C

0°C
NASA/TM—2012-217285 12 

Cycle Life Performance 

Cycle life testing was initiated in October 2010 and as of April 2011, the DD cells cycling at 20 °C had completed 

205 cycles. Figure 9 compares the capacity of the five cells being cycled. The noticeable decrease in capacity every 

tenth cycle corresponds to a C/2 discharge. Although the cells have demonstrated consistent performance with a low 

capacity fade rate, the cells that began with a slightly higher capacity have shown slightly less fade than the remaining 

cells. Table 8 shows the original capacity and capacity retention to 205 cycles as a percentage of the initial capacity. 

Initial capacity for the cells is taken as cycle 2 on the plot, which does not include diagnostics performed prior to 

cycling. On average, the cells have retained 96.2 percent of the initial capacity after 205 cycles under life testing 

conditions. Cells 41 and 48, the cells with the highest initial capacities, also have slightly higher capacity retention 

after 205 cycles. Assuming the capacity continues to fade at the same rate, the cells will reduce to 80 percent capacity 

retention after 946 cycles. The cells will continue to cycle until this point has been reached. 

Figure 9.—Cycle life capacity of DD cells at 20 °C. 

TABLE 8.—20 °C CYCLE LIFE CAPACITY 

RETENTION TO 205 CYCLES 

 

8.5

9

9.5

10

10.5

11

11.5

18

15222936435057647178859299

106113120127134141148155162169176183190197204

Capacity Ah

Cycle Number

Cell 21

Cell 30

Cell 32

Cell 41

Cell 48

Room TempAvg

Cell Initial Ah

% of initial

capacity

retained

21 10.89 95.2%

30 10.85 96.0%

32 10.89 95.6%

41 10.90 97.0%

48 10.98 97.0%

Average 10.90 96.2%
NASA/TM—2012-217285 13 

As of March 2011, four cells cycling with a 0 °C discharge have completed 99 cycles (Fig. 10). As noted on the 

plot, there were several occasions during which the temperatures were not correctly matched to charge or discharge 

states. For example, during the period marked “temperature mismatch,” cycles 12 through 19, the cells began to 

discharge while the chamber temperature was still at 20 °C, leading to a higher capacity than expected at 0 °C. From 

cycles 30 to 63 the environmental chamber was experiencing icing issues. Several cells experienced colder 

temperatures due to their proximity to the ice formation, and some were further away and were not as greatly affected. 

Charge data for cell 37, which experienced the most severe temperature drop due to its location in the chamber, is in 

Figure 11. Cycles 9 and 118 in the plot represent cycles before and after the icing occurred. It is obvious from the 

charge curve of Cycle 57 that the average charge voltage was higher than the other cycles by roughly 1 percent during 

the icing period. The charge curve for Cycle 118, well after the temperature conditions were brought back to normal, 

returned to the original profile. The cells experienced brief periods of rest time intermittently while various attempts 

were made to repair the chamber, however, the issue was solved after cycle 63 and the cells have been cycling 

continuously since. Figure 10 clearly shows the difference in capacity during the period described above. 

Figure 10.—Cycle life discharge capacity with 0 °C discharge. 

Figure 11.—Cell 37 charge curves. 

8.5

9

9.5

10

10.5

11

11.5

159

13172125293337414549535761656973778185899397

101105

Capacity Ah

Cycle Number

Cell 33

Cell 37

Cell 39

Cell 43

Low Temp Avg

Chambericing

Temperature mismatch

3

3.2

3.4

3.6

3.8

4

4.2

0 2 4 6 8 10 12

CellVoltage

V

Charge Capacity Ah

Cycle 9

Cycle 57

Cycle 118
NASA/TM—2012-217285 14 

Table 9 lists capacity retention for individual cells, including that after 99 cycles the cells have retained an average 

of 98.4 percent. Cell 49 is not listed in Table 9 as testing was halted early in cycling due to failure for unknown 

reasons. In comparison, the cells cycling at 20 °C retained 98.3 percent of their initial capacity after 99 cycles. 

Figure 12 illustrates the trends of both cycle life tests and shows that capacity fade does not seem to be affected by 

discharge temperature. 

TABLE 9.—0 °C DISCHARGE CYCLE LIFE 

CAPACITY RETENTION TO 99 CYCLES 

Figure 12.—Comparison of 20 °C vs. 20/0 C cycle life. 

Cell Initial Ah

% of initial

capacity

retained

33 9.93 98.7%

37 9.95 99.3%

39 10.04 97.6%

43 9.99 97.9%

Average 9.98 98.4%

8.5

9

9.5

10

10.5

11

11.5

18

15222936435057647178859299

106113120127134141148155162169176183190197204

Capacity Ah

Cycle Number

Room Temp Avg

Low Temp Avg

Temperature

mismatch

Chambericing

for Low Temp

tests
NASA/TM—2012-217285 15 

Conclusions 

The Saft DD baseline cells delivered 157.2 Wh/kg at 20 and 0 °C testing yielded roughly 90 percent of the energy 

at 20 °C, while increasing the discharge current to a C/2 rate decreased the energy of the cell by roughly 10 percent. 

Minor differences in performance were observed when the cells were tested with a 0 °C discharge only versus 20/0 °C 

charge and discharge conditions. Cycle life tests revealed that the capacity fade rate to 205 cycles has not been affected 

by a 0 °C discharge versus tests run completely at 20 °C. Although these cells serve as a baseline and are not designed 

to meet the KPP metrics for capacity and cycle life, it is encouraging that the capacity and cycle life performance are 

not greatly affected by lower temperatures listed as the KPP metrics. Data collected for these cells will serve as a basis 

for comparison with future cell builds to track the progress of cell development for the High Efficiency Space Power 

Systems Project. 

References 

1. Mercer, Carolyn R., Amy L. Jankovsky, Concha M. Reid, Thomas B. Miller, and Mark A. Hoberecht , “Energy 

Storage Technology Development for Space Exploration,” NASA Glenn Research Center, Cleveland, OH, 

NASA/TM—2011-216964, prepared for the Space 2010 Conference and Exposition sponsored by the American 

Institute of Aeronautics and Astronautics Anaheim, CA, August 30 - September 2, 2010. 

2. Miller, Thomas B., Dr. Robert Staniewicz, Dr. Chengsong Ma, and Steve Hafner, “Integrating Novel Lithium-ion 

Cell Components Into Saft America’s Aerospace Manufacturing Process,” National Aeronautics and Space 

Administration Glenn Research Center, Cleveland, OH, to be published. 
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Performance Assessment of Baseline Cells for the High Efficiency Space Power Systems 

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13. SUPPLEMENTARY NOTES

14. ABSTRACT

Abstract The Enabling Technology Development and Demonstration (ETDD) Program High Efficiency Space Power Systems (HESPS) 

Project, formerly the Exploration Technology Development Program (ETDP) Energy Storage Project is tasked with developing advanced 

lithium-ion cells for future NASA Exploration missions. Under this project, components under development via various in-house and 

contracted efforts are delivered to Saft America for scale-up and integration into cells. Progress toward meeting project goals will be 

measured by comparing the performance to these cells with cells of a similar format with Saft’s state-of-the-art aerospace chemistry. This 

report discusses the results of testing performed on the first set of baseline cells delivered by Saft to the NASA Glenn Research Center. This 

build is a cylindrical “DD” geometry with a 10 Ah nameplate capacity. Testing is being performed to establish baseline cell performance at 

conditions relevant to ETDD HESPS Battery Key Performance Parameter (KPP) goals including various temperatures, rates, and cycle life 

conditions. Data obtained from these cells will serve as a performance baseline for future cell builds containing optimized ETDD HESPSdeveloped materials. A test plan for these cells was developed to measure cell performance against the high energy cell KPP goals. The goal 

for cell-level specific energy of the high energy technology is 180 Wh/kg at a C/10 discharge rate and 0 °C. The cells should operate for at 

least 2000 cycles at 100 percent DOD with 80 percent capacity retention. Baseline DD cells delivered 152 Wh/kg at 20 °C. This number 

decreased to 143.9 Wh/kg with a 0 °C discharge. This report provides performance data and summarizes results of the testing performed on 

the DD cells. 

15. SUBJECT TERMS

Lithium batteries; Strong batteries; Electric batteries; Electrochemical cells; Energy storage; Space missions; Spacecraft power 

supplies; Electric power supplies 

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