The workshop was attended by representatives from industry and government. The requirements for energy storage and the plans for battery development were reviewed. The workshop followed a debate format, with the objective of recommending improvements to the development plans presented by NASA and the Air Force. The issues addressed were: (1) significant technology deficiencies which can be identified; (2) adequacy of current and proposed programs to resolve the technology deficiencies identified; (3) additional tasks which should be undertaken, including benefits and timing; and (4) lowest priority items in the presently planned program, both in content and in timing

Ford, F. E.

Sparks, R. H.

English

NASA Technical Reports Server

BATTERY WORKSHOP 
Cochairmen: Richard  H. Sparks 
TRW Defense & Space Systems 
and Floyd E. Ford 
NASA Goddard Space F l i g h t  Center  
The b a t t e r y  workshop w a s  a t t e n d e d  by 18 people  from i n d u s t r y  and govern- 
ment. R e v i e w  o f  t h e  requi rements  f o r  energy s t o r a g e  and t h e  p l a n s  f o r  b a t t e r y  
development w a s  v i g o r o u s ,  w i t h  widespread p a r t i c i p a t i o n .  
a debate  format ,  w i t h  t h e  o b j e c t i v e  of  recommending improvements t o  t h e  develop- 
ment p l a n s  p r e s e n t e d  by NASA and t h e  A i r  Force.  The i s s u e s  a d d r e s s e d  w e r e  
The workshop fol lowed 
(1) S i g n i f i c a n t  technology d e f i c i e n c i e s  which can be i d e n t i f i e d  
(2) Adequacy of  c u r r e n t  and proposed programs t o  r e s o l v e  t h e  technology 
d e f i c i e n c i e s  i d e n t i f i e d  
( 3 )  A d d i t i o n a l  t a s k s  which should  be undertaken,  i n c l u d i n g  b e n e f i t s  and 
t i m i n g  
( 4 )  Lowest p r i o r i t y  i t e m s  i n  t h e  p r e s e n t l y  planned program, b o t h  i n  con- 
t e n t  and i n  t i m i n g  
The workshop w a s  l i m i t e d  t o  2 hours ,  which n e c e s s a r i l y  r e s t r i c t e d  t h e  depth  of  
o u r  review; however, a g e n e r a l  consensus w a s  reached  by b o t h  workshop subgroups.  
The main theme of  t h e i r  conclus ions  w a s  t h a t  t h e  power system t rade-of f  s t u d i e s  
f o r  l a r g e  power systems (25 kW and l a r g e r )  have n o t  been adequate ly  performed: 
(1) E a r l y  1970 ' s  b a t t e r y  technology i s  g e n e r a l l y  compared w i t h  p r o j e c t e d  
1980's f u e l  c e l l  c a p a b i l i t y .  
( 2 )  Smal l -ba t te ry  d a t a  are compared w i t h  a s i n g l e  la rge- fue l -ce l l - sys tem 
d a t a  base.  
( 3 )  Cost t r a d e - o f f s  do n o t  i n c l u d e  redundancy and s c a l i n g  f a c t o r s  f o r  
l a r g e r  b a t t e r y  and fuel, c e l l  systems. 
( 4 )  E f f e c t s  of  bus v o l t a g e  on t h e  energy-storage-system concept  have n o t  
been i d e n t i f i e d .  
The consensus o f  t h e  workshop was t h a t  t h e  b a t t e r y  development program is  under- 
scoped because t h e  t r a d e - o f f  s t u d i e s  have n o t  a d e q u a t e l y  cons idered  b a t t e r y  ad- 
vanced technology c a p a b i l i t y  and r e l a t i v e l y  low c o s t  a t  t h e  system l eve l ;  hence,  
t h e  p r i o r i t y  a s s o c i a t e d  w i t h  advanced b a t t e r y  development i s  t o o  low. 
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The most s i g n i f i c a n t  technology d e f i c i e n c i e s  i d e n t i f i e d  by t h e  workshop 
were as fol lows:  
(1) Ba t t e ry  l i f e  development goals  do n o t  m e e t  mission-planning goa ls  and 
ground ru l e s :  
(a) Low-Earth-orbit missions are be ing  planned based on a 10-year 
l i f e .  Bat te ry  development goa ls  i n  t h e  p re sen t  programs are 5 years .  A 10- 
year  l i f e  requirement is  needed. 
(b) Geosynchronous-orbit missions are being planned wi th  l i f e s  ranging 
from 7 t o  15 years .  Bat te ry  development goals  are 10 years .  A 15-year l i f e  
requirement may be needed. 
(2) Low-cost b a t t e r i e s  are widely d iscussed;  however, mission requirements 
are based on low-cost b a t t e r y  systems which inc lude  t o t a l  system r e l i a b i l i t y ,  
l i f e ,  and maintenance cos t s .  - The low-cost b a t t e r y  concept is  no t  t o t a l l y  con- 
s i s t e n t  wi th  low-cost b a t t e r y  system concepts:  
(a)  Bat te ry  c o s t s  are a l ready  r e l a t i v e l y  low; bu t  implementation c o s t s  
w i t h i n  t h e  aerospace sof tware  and hardware systems are high. 
cos t  reduct ions  c i t e d  i n  t h e  workshop are 
Implementation 
. To inc rease  b a t t e r y  l i f e  t o  reduce replenishment c o s t s  
. To reduce b a t t e r y  redundancy weight and complexity t o  save  i n i -  
t i a l  c o s t s  and launch c o s t s  
(b) Batteries are small (less than  60 Ah), n e c e s s i t a t i n g  t h e  use of  
mul t ip l e  b a t t e r y  assemblies  and c o n t r o l  e l e c t r o n i c s  f o r  25- t o  100-kW systems. 
Cost d a t a  presented  a t  t h e  workshop show a s i g n i f i c a n t  cos t  l everage  by reducing 
the  number o f  components i n  t h e  b a t t e r y  system. A 100- t o  500-Ah b a t t e r y  s i z e  
c a p a b i l i t y  is needed. 
(c)  P a r t s  sc reening  c o s t s  have s i g n i f i c a n t  leverage  on b a t t e r y  c o s t s ;  
however, wi thout  s c reen ing  of p a r t s  made wi th  commercial p rocesses ,  r e l i a b i l i t y  
and hence maintenance c o s t  are impacted s t rong ly .  Refined screening  methods 
commensurate w i t h  t h e  maintenance cos t  models be ing  planned should be developed. 
(d) Ba t t e ry  system redundancy is  very c o s t l y  both i n  weight and i n  
e l e c t r o n i c s  complexity. A low-cost, low-weight redundancy concept i s  not  a v a i l -  
ab l e  and needs development. 
(3)  Deep-discharge, l ong- l i f e  app l i ca t ions  f o r  b a t t e r i e s  are no t  w e l l  cle- 
veloped. Operating convent ional  b a t t e r i e s  a t  deep depths of  d i scharge  (DOD) i s  
t h e  b e s t  s i n g l e  way t o  reduce energy-storage-system s p e c i f i c  weight.  Present  
nickel-cadmium b a t t e r y  s t u d i e s  are based on 15-percent DOD f o r  3.5- t o  5-year 
low-Earth-orbit missions.  Increas ing  DOD t o  60 percent  f o r  a 10-year l i f e  i s  a 
major improvement which should be developed t o  m e e t :  t h e  mission goals  presented :  
284 
(a )  Nickel-cadmium b a t t e r i e s  can be operated a t  deeper depths of dis-  
charge (up t o  85 percent  f o r  some app l i ca t ions )  by using new ope ra t ing  methods 
and newly developed p l a t e  and sepa ra to r  processes .  The nickel-cadmium b a t t e r y  
should be developed f o r  a 10-year l i f e  a t  greater than  20-percent DOD. 
(b) Nickel-hydrogen b a t t e r i e s  are being developed by t h e  A i r  Force 
f o r  a 1-year l i f e  a t  80-percent DOD and f o r  a 5-year l i f e  a t  60-percent DOD i n  
low Earth o r b i t s .  The c a p a b i l i t y  should be improved t o  60-percent DOD f o r  
10 yea r s ,  and a low-Earth-orbit f l i g h t  experiment should be flown a t  60-percent 
DOD t o  v a l i d a t e  the  system i n  space. 
( 4 )  Peak loads r equ i r ing  load-level ing b a t t e r y  systems w e r e  shown by both 
A i r  Force and NASA mission models i n  1987-1988. No technology is  a v a i l a b l e  t o  
support  load-level ing missions wi th in  reasonable  weight c o n s t r a i n t s .  This  mis- 
s i o n  requirement should be immediately t r a n s l a t e d  i n t o  energy-storage-system 
requirements f o r  f u r t h e r  development. 
(5) Large bulk-energy-storage b a t t e r y  systems are not  available €or  100-kW 
and l a r g e r  systems i n  t h e  1990's.  Work i n  sodium-sulfur ,  advanced l i t h ium,  and 
l a r g e  nickel-hydrogen systems needs t o  be  done t o  i d e n t i f y  p o t e n t i a l  capabi l i -  
t i e s  and t o  develop a l a r g e  bulk-energy-storage system f o r  t h e  l a r g e r  space 
p l a t  f o rms . 
Other technology d e f i c i e n c i e s  w e r e  c i t e d  by t h e  workshop but  had lower p r i o r i -  
t i e s  than  t h e  preceding i t e m s .  
During t h e  workshop d i scuss ions ,  t h e  group commented on cu r ren t  and pro- 
posed NASA and A i r  Force programs. The comments are summarized as follows: 
(1) Overall funding f o r  b a t t e r y  systems i s  too  low t o  m e e t  t h e  large-power- 
system program goals .  NASA has underestimated t h e  p o t e n t i a l  of b a t t e r i e s  f o r  
l a r g e  space systems by us ing  over ly  conserva t ive  b a t t e r y  performance da ta  f o r  
system trade-off  s t u d i e s ,  thus  causing a low p r i o r i t y  t o  be  given t o  advanced 
b a t t e r y  development. Emphasis on b a t t e r y  development should be increased.  
(2)  A 100-Ah c e l l  program s ta r t  i n  1978 i s  needed; however, t h e  scope of 
t he  planned f e a s i b i l i t y  program should be expanded t o  encompass a c e l l  s i z e  
range of 100 t o  1000 Ah t o  provide a more use fu l  da t a  base  f o r  large-power- 
system designs.  
( 3 )  Very l i m i t e d  s t u d i e s  of n i c k e l  e l ec t rodes  and nickel-cadmium c e l l  de- 
s igns  f o r  long l i f e  are planned and funded. A much more ex tens ive  concent ra t ion  
on e lec t rochemica l ly  impregnated and o t h e r  more phys ica l ly  s t a b l e  e l ec t rodes  
should be i n i t i a t e d  and d i r e c t e d  toward 10-year l i f e  cyc le  s e r v i c e ,  inc luding  
. b . . a  
(a) More fundamental s t u d i e s  of deep-discharge cyc le  phenomena 
(b) More i n v e s t i g a t i o n  of opera t ing  methods which do no t  o v e r s t r e s s  t h e  
e l ec t rode  s t r u c t u r e  
The payoff w i l l  be f o r  both NiCd and NiH2 b a t t e r i e s .  Other comments on e x i s t i n g  
programs w e r e  va r i ed  and, i n  genera l ,  f e l l  w i t h i n  t h e  scope of those  summarized. 
285 
The workshop worked toward a summary of a d d i t i o n a l  t a sks  needed t o  meet 
the  NASA and A i r  Force mission ob jec t ives .  Several a d d i t i o n a l  t a sks  w e r e  iden- 
t i f  i ed :  
(1) The f i r s t  recommendation w a s  t o  perform updated spacec ra f t  system-level 
trade-off s t u d i e s  comparing e x i s t i n g  and f u t u r e  b a t t e r y  systems, inc luding  f u e l  
c e l l  systems. The s t u d i e s  should use p ro jec t ed  1980-82 c a p a b i l i t y  and 1985-87 
c a p a b i l i t y  and should determine s e n s i t i v i t y  t o  d i f f e r e n t  types of b a t t e r i e s  and 
f u e l  cel ls .  Weight, c o s t ,  redundancy, l i f e ,  and control-system-complexity sen- 
s i t i v i t y  v a r i a b l e s  should be included:  
(a) System cos t  and weight t rade-of fs  should be performed f o r  candi- 
da t e  energy s t o r a g e  systems. 
(b) System redundancy and refurbishment t rade-of fs  should be performed 
f o r  candida te  energy s to rage  systems. 
The workshop noted t h a t  maintenance of heavy components i n  space through re fur -  
bishment may not  be p r a c t i c a l  and w i l l  be  very expensive.  
( 2 )  The second recommendation w a s  t o  i n i t i a t e  development of s u b s t a n t i a l l y  
l a r g e r  b a t t e r y  c e l l s  wi th  a c t i v e  cool ing  provis ions  which can be adapted t o  
l a r g e  space systems. Development should be centered  on a 250- t o  500-Ah c e l l  
o r  b a t t e r y  des ign ,  s c a l a b l e  from 100 t o  1000 Ah f o r  system design f l e x i b i l i t y .  
( 3 )  The t h i r d  recommendation w a s  t o  i n i t i a t e  a near-term NASA program t o  
implement t h e  nickel-hydrogen b a t t e r y  system i n t o  NASA systems s t u d i e s .  An 
e a r l y  low-Earth-orbit f l i g h t  experiment should be performed a t  deep depths of 
d i scharge  (40 t o  60 percent )  t o  assess t h e  technology c a p a b i l i t y  and t o  de te r -  
mine ref inements  needed f o r  l a r g e r  space c e l l  development. 
( 4 )  The f o u r t h  recommendation w a s  t o  i n c r e a s e  funding t o  cover a broader  
b a t t e r y  technology program f o r  l a r g e  long- l i f e  systems, inc luding  
(a) 10-year Low-Earth- and geosynchronous-orbit system l i f e  
(b) Lower system c o s t s  by e l imina t ing  system complexity: 
Fewer b a t t e r i e s  
Low-cost redundancy concept 
Minimum replenishment 
( c )  Increased  monitor ing of DOE technology developments t o  select  
t imely technology sp inou t s  f o r  space app l i ca t ions  (Lithium, so- 
dium, and o t h e r  h igh  s p e c i f i c  energy system developments should 
be monitored c lose ly . )  
(d) I n v e s t i g a t i o n  of technology requi red  t o  support  high-voltage 
power systems 
286 
The workshop encountered d i f f i c u l t y  i n  i d e n t i f y i n g  t h e  t h r e e  lowest 
p r i o r i t y  technology items i n  t h e  NASA plan.  The work planned is narrow and 
needs t o  be widened. However, p r i o r i t y  recommendations w e r e  developed t o  be 
o f f e red  i n  a s s i s t i n g  f u t u r e  plans as fol lows:  
(1) Increas ing  t h e  s p e c i f i c  energy of NiCd ce l l s  should receive much lower 
p r i o r i t y  than  inc reas ing  t h e  l i f e  and u t i l i z a t i o n  of s t o r e d  energy a t  deeper 
depths of discharge.  The l a r g e s t  o v e r a l l  system c o s t  and weight savings f o r  
t he  l a r g e r  space  systems planned w i l l  r e s u l t  from doubling t h e  b a t t e r y  l i f e  and 
inc reas ing  depth of d ischarge  t o  40 t o  60 percent .  Small i nc reases  i n  s p e c i f i c  
energy are of l i t t l e  o v e r a l l  system value.  
(2)  Higher p r i o r i t y  should be placed on fol lowing DOE high-energy-density 
systems work, i nc lud ing  
(a)  Close s u r v e i l l a n c e  
(b) I d e n t i f y i n g  e a r l y  sp inout  f o r  space t o  m e e t  1990-2000 goals  
A low p r i o r i t y  should be placed on s t a r t i n g  new developments p a r a l l e l i n g  DOE 
work u n t i l  a good b a s i s  f o r  sp inout  is  e s t ab l i shed .  
(3) Highest p r i o r i t i e s  should be appl ied  t o  long- l i fe  b a t t e r y  systems 
which can d e l i v e r  a high percentage of s t o r e d  energy t o  t h e  power system, i n  
con t r a s t  t o  s h o r t - l i f e  s c i e n t i f i c  system b a t t e r y  requirements.  Space system 
cos t -e f fec t iveness  models presented  show t h a t  s h o r t - l i f e  energy s t o r a g e  systems 
are extremely expensive.  
These workshop conclusions and recommendations w e r e  p resented  before  t h e  
e n t i r e  symposium. No disagreement w a s  rece ived  from t h e  f l o o r .  The workshop 
surmparies w e r e  t h e r e f o r e  documented i n  t h i s  r e p o r t  w i th  minimum changes f o r  
c l a r i f i c a t i o n .  
287 


Battery workshop

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