The effects of four different charge methods on the energy conversion efficiency of 300 ampere hour lead acid traction cells were investigated. Three of the methods were positive pulse charge waveforms; the fourth, a constant current method, was used as a baseline of comparison. The positive pulse charge waveforms were: 120 Hz full wave rectified sinusoidal; 120 Hz silicon controlled rectified; and 1 kHz square wave. The constant current charger was set at the time average pulse current of each pulse waveform, which was 150 amps. The energy efficiency does not include charger losses. The lead acid traction cells were charged to 70 percent of rated ampere hour capacity in each case. The results of charging the cells using the three different pulse charge waveforms indicate there was no significant difference in energy conversion efficiency when compared to constant current charging at the time average pulse current value

Smithrick, J. J.

English

NASA Technical Reports Server

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DOE/NASA/51 044-22 
NASA TM-82709 
I 
AS A-TM-82709 19820002630 
i Effect of Positive Pulse Charge Waveforms 
.. ---
on the Energy Efficiency of Lead·Acid 
Traction Cells 
John J. Smith rick 
National Aeronautics and Space Administration 
Lewis Research Center 
September 1981 
Prepared for 
U.S. DEPARTMENT OF ENERGY 
Conservation and Renewable Energy 
Office of Vehicle and Engine R&D 
NOV 12 1981 
LANGLEY Rrsr:-A.R~ -, ~ENT£R 
L:SP-G.RY. NASA 
HMi?TCN. VIRGINIA 
I 
I 
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https://ntrs.nasa.gov/search.jsp?R=19820002630 2020-03-21T11:54:29+00:00Z
NOTICE 
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- - --- --- - - -~-- - -
- - --- - --- - - ~ 
DOE/NASA/51 044-22 
NASA TM-82709 
Effect of Positive Pulse Charge Waveforms on the Energy 
Efficiency of Lead·Acid Traction Cells 
John J. Smith rick 
National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland, Ohio 44135 
September 1981 
Work pe rformed for 
U.S. DEPARTMENT OF ENERGY 
Conservation and Renewable Energy 
Office of Vehicle and Engine R&D 
Washington, D.C. 20545 
Under Interagency Agreement DE-AI01-77CS51 044 
I 
, 
EFFECT OF POSITIVE PULSE CHARGE WAVEFORMS ON THE ENERGY 
EFFICIENCY OF LEAD-ACID TRACTION CELLS 
by John J. Smithrick 
National Aeronautics and Space Administration 
Lewis Researach Center 
Cleveland, Ohio 44135 
ABSTRACT 
The effects of four different charge methods on the energy conversion 
efficiency of 300 ampere-hour lead-acid traction cells were investigated. 
Three of the methods were positive pulse charge waveforms; the fourth, a con-
~ stant current method, was used as a baseline of comparison. The positive 
0\ 
0\ pulse charge waveforms were; 120 Hz full wave rectified sinusoidal (FWSR), 120 
I ~ Hz silicon controlled rectified (SCR); and 1 kHz square wave (SW). The con-
stant current charger was set at the time average pulse current of each pulse 
wave form, which was 150 amperes. The energy efficiency does not include 
charger losses. 
The lead-acid traction cells were charged to 70% of rated ampere-hour 
capacity in each case. The results of charging the cells using the three dif-
ferent pulse charge waveforms indicate there was no significant difference in 
energy conversion efficiency when compared to constant current charging at the 
time average pulse current value. 
INTRODUCTION 
Charging methods could effect battery energy conversion efficiency, and 
should be a consideration in evaluating possible applications of secondary 
batteries . The energy conversion efficiency, for instance, of traction bat-
teries for an electric vehicle is a parameter which could impact vehicle oper-
ating cost. Various methods of charging batteries have been proposed and re-
viewed. (1, 2, 3, 4, 5 , 6 , 7, 8). However, only limited information about 
the effect of these charging methods on the energy conversion efficiency of 
secondary batteries exists. Some authors indicate that excessive gassing dur-
ing charge is detrimental to energy conversion efficiency and suggest that 
charge control should be based on gas evolution. Others suggest that pulse 
charging c ould improve battery energy conversion efficiency. 
A test program was ini tiated to expand the data base on the effect of 
charge methods on battery energy conversion efficiency. This program was 
sponsored by the U.S. Department of Energy, in response to the need to develop 
a viable electric vehicle for urban transportation. Four charge methods were 
selected and their effect on the energy conversion efficiency of 300 Ampere-
hour lead acid traction cells was investigated. Three of the charge methods 
were different positive pulse charge waveforms; 120 Hz full wave rectified 
sinusoidal (FWRS), 120 Hz silicon controlled rectified (SCR), and 1 kHz square 
wave (SW) . The fourth was a standard constant current method use d as a base-
line of comparison. These charge methods were considered realistic options 
for charging electric vehicle batteries. The energy efficiency does not in-
clude charger losses. 
In this paper, the results of positive pulse charge waveforms on the en-
ergy conver sion efficiency of 300 ampere-hour lead-ac id tractio n cells are 
prese nted and discussed. 
EXPERIMENTAL 
Cell Chargers 
The positive pulse chargers and their specifications were: 120 Hz full 
wave rectified chargers sinusoidal (FWRS), voltage range 0 to 8 Volts (PEAK) 
current range, 0 to 1000 amperes, adjustable peak to average current and ad-
j ustable firing angle; 1 kHz square waveform (SW), voltage range 0 to 8 volts, 
current range 0 to 1000 amperes adjustable ratio of peak to average current; 
and adjustable duty cycle; and a constant current charger, voltage range 0 to 
8 volts and a current range 0 to 1000 amperes. Representative charge current 
waveforms, calculated from oscilloscope voltage traces measured across a shunt 
during charge, are illustrated in figures 1 to 4. Zero charge current oc-
curred when charger power supply voltage equals the cell voltage. . 
The FWRS charger was selected on the basis of low cost potential relative 
to a constant voltage charger which requires close voltage regulation (9). 
Similarly, the FWRS charger would be inexpensive compared to a constant cur-
r e nt charger. Simple circuitry should also result in greater reliability, and 
l ighter weight which could be a factor in selecting a charger for on-board 
electric vehicle use. SCR and constant current chargers were selected as rep-
r esentative of present charge methods. The 1 kHz SW charger was selected be-
cause the circuitry was similar to existing electric vehicle chopper control-
ler circuitry, which could be utilized for an on-board charger. The FWRS and 
SCR chargers were designed and fabricated at the NASA-Lewis Research Center. 
The 1 kHz and constant current chargers were designed and fabricated by the 
General Electric Company (10) . 
MEASUREMENT AND PROCEDURES 
For this set of experiments, the quantities measured and their accuracies 
were: average charge current (+ 0.3 %), peak charge current (+ 3%), peak to 
average charge current ratio (+-3%), discharge current (+ 0.3%), ampere-hours 
(+ 0 .5 %), and cell voltage (+ 0 . 3%). -
- The average charge current was calculated from the average voltage mea-
sured with an integrating digital voltmeter across a non- inductive current 
shunt. The peak charge current was calculated from peak voltage measured 
across a non-inductive shunt with an oscilloscope. From thes e values, the 
peak to average currrent ratio was calculated. The discharge current was also 
calculated from the voltage measured across a non-inductive shunt. A current 
integrator (ampere-hour meter) was used to measure the charge integral 
(ampere-hours) put into a cell during charge and taken out of a cell during 
discharge. The cell voltage during charge and discharge was recorded on a 
strip chart recorder and also monitored using an integrating digital voltmeter. 
The coulombic efficiency was obtained as follows. First the cells were 
charged to 70 % of rated ampere-hour capacity. This was followed by a dis-
charge at 100 amperes to a 1.75 volt cutoff at which point t h e current was 
reduc e d to 75 amperes and the discharge resumed. When the c e ll again reached 
the 1.75 volt cutoff, the current was reduced to 50 amperes . At the point 
where the cell voltage dropped to 1.75 volt while at the 50 a mp discharge 
rate, the discharge was terminated and the capacities delive~ed during the 
2 
three segments of the discharge were noted . A typical set of results for a 
discharge sequence as described here are listed in table 1. Similarly, the 
total capacity delivered to the cell during the cycle was obtained from the 
cu rrent integrator. Coulombi c efficiency was calculated as a ratio of total 
ampere-hours out of a cell during discharge to the total ampere-hours into the 
cell during charge. 
The energy efficiency was calculated as a ratio of the total energy out 
of a cell during discharge to the total energy into a cell during charge. Th e 
total energy out of a cell during discharge was calculated by summing the pro-
duct of measured charge integral and average cell voltage at each current 
level. The average cell voltage was obtained from a strip chart recording of 
cell voltage as a function of time. A typical energy output determination 1S 
shown in table 1. The total energy into a cell during charge was obtained as 
follows: The power into the cell as a function of time was measured and re-
c orded using a conventional watt meter. From this data, a curve of 
as a function of time was made, and the integrated value of this curve was the 
total energy into the cell . The energy efficiency does not take into account 
the charger losses. 
For each charge method, the charge was terminated when the cell was 
charged to 70% of its rated ampere-hour capacity. This charge termination was 
selected due to the onset of excessive gassing which could produce an "aging 
ef fe ct" during the duration of the test, masking the influence of charge 
method on the cell energy efficiency. 
RESULTS AND DISCUSSION 
Representative waveforms used in this experiment are illustrated in fig-
ures 1-4 . The waveforms are substantially different. However, the time aver-
age pulse charge current for each waveform was the same (150 amperes, cia 
ra te) . This enabled a comparison of the effectivenes of the four charge wave-
form methods. 
The results of charging 300 ampere-hour lead- acid traction cells, using 
the four different charge methods, are summarized in table 2. A statistical 
analysis of the energy efficiency data was performed. Confidence intervals 
were calculated based on T-test at the 95 % confidence level using a pooled 
standard deviation (11). 
Figure 5 summarizes the average cell energy conversion efficiency and 
confidence intervals for each of the charge methods. The spread in the data 
indicate no significant difference in the average cell energy conversion effi-
ciency using the 120 Hz FWRS charger, the SCR charger, the 1 kHz SW charger, 
or the constant current charger . The energy efficiency did not include 
charger losses. 
Results of this investigation suggest that a relatively inexpensive full 
wave rectified sinusoidal charger could be used to charge 300 ampere- hour 
lead-acid traction cells with no significant loss in cell energy conversion 
efficiency when compared to more expensive charge methods. A 1 kHz square 
wave charger could also be used with no loss in cell energy conversion effi-
ciency and this suggests the possibility of utilizing existing electric vehi-
cle chopper controller circuitry for an on-board charger. Pulse charging, of 
the type investigated, did not lead to an increase in energy efficiency over 
that of the constant current charge method. 
3 
I 
The effect of pulse charg ing on the charge/discharge cycle life of 300 
ampere-hour lead- acid t raction cells is unknown at this time. However, previ-
ously reported work (12), using the same charge methods, but small (5 ampere-
hour) nickel - zinc cells sugges t there may not be as effect on cycle life. 
CONCLUDING REMARKS 
A rela t ively inexpensive full wave rectified sinusoidal charges could be 
u se d to charge 300 ampere- hour lead-acid traction cells with no significant 
lo ss in cell energy conversion efficiency when compared to more expensiv e 
charge methods. The SCR and 1kHz SW chargers also could be used with no sig-
ni fican t loss in cell energy conversion efficiency. The 1kHz charger is a 
contende r for an on board electric vehicle charger because it could utilize 
existing electric vehicle chopper controller circuitry. 
REFERENCES 
1. Smithrick, J. J.: Rapid, Efficient Char ging of Lead- Acid and Nickel-
Zinc Traction Cells. NASA TM-78901, 19 78 . 
2. Gros s, S.: Rapid Charging of Lead-Acid Batteries. IEEE Conference 
Record of the 1973 Eighth Annual Meeting of the IEEE Industry Applica-
t ions Society, Institute of Electrical and Electronics Engineering, Inc. 
pp. 905 - 912. 
3. Mas, J . A.: The Charging Process . 
tional Electric Vehicl e Symposium. 
228-246. 
Proceedings of the Second Interna-
Electric Vehicle Council, 1971, pp. 
4. Sparks, R. H.: Rapid Charging Batteries for Electric Propulsion Systems. 
SAE Paper 720109, Jan. 1972 . 
5. Romanov, V. v.: Improvement of certain operational characteristics of 
Silver- Zinc Storage Batteries. FSTC-HT-23 - 1563-71, Army Foreign Sciences 
and Technology Center, 1972. (AD-742887, Translation of Vestn. Elektro-
prom . (Moscow), Vol. 31 no . 9, 1966, pp. 26 - 29 . ) 
6. Wagner, o. C . ; Williams, D. D. : Investigation of Charging Methods of 
Nickel- Cadmium Batteries. 26th Annual Power Sources Conference, PSC Pub-
lications Committee, 1974, pp. 96 - 99 . 
7. Rippel , W. E.: Charge Acceptance Characteristics of the Lead-Acid Cell. 
Proceedings of the Second International Electric Vehicle Symposium, Elec-
tric Vehicle Council, 1971, pp. 247- 274. 
8. Wagner, o. C.; Williams, D. D.: Investigation of Charging Methods for 
Nickel-Cadmium Batteries. ECOM-4355 U. S. Army Electronics Command, 
1975 . (AD-A016132). 
9. Muel ler, G. A.: The Gould Battery Handbook. Gould, Inc., Mendota 
Heigh ts, Minn., 197 3 . 
10. Steige rwald, R. L.: Pulse Battery Charger Employing 1000 Ampere Transis-
tor Switches. IEEE Conference Record of the 1977 Twelfth Annual Meeting 
of the IEEE Industry Applications Society, Institute of Electrical and 
Elec tronics Engineers, Inc., 1977, pp. 1127-1132. 
11. Dixon, W. J . ; and Massey, F. J . , Jr.: Introduction to ,S tat istical Anal-
YSlS . Third Ed . , McGraw Hill Book Co . , Inc. 1969. 
4 
-~ ----------
TABLE I . - CHARGE ( AMPERE-HOUR) AND ENERGY (WATT-
HOUR) DETERMINATION OF A REPRESENTATIVE 300 
A~WERE-HOUR LEAD-ACID TRACTION CELL 
Dis charge Charge Average Energy Cutoff 
current, ou tput , cell output, vo1tage,* 
amp, amp-hr voltage, watt- hr V 
V 
100 139 . 5 1.87 260.9 1. 7 5 
75 27 .4 1.81 49.6 1. 75 
50 30 . 4 1.82 55.3 1. 75 
19 7. 3 365.8 
*Vo1tage at which discharge was terminated. 
5 I 
I 
I 
TABLE II. - RESULTS OF CHARGING 300 AMPERE-HOUR LEAD-ACID TRACTION CELLS 
USING REPRESENTATIVE WAVEFORMS 
Ce 11 Charge waveform AH1 AH2 Cou1ombic WH3 WH4 Energy Percent 1 0 1 0 
efficiency efficiency charged 
AHO/ AH1 ) WHO/WH1 ) AJ 1/300 
percent percent 
2 Constant current (fig. 1) 210 204 97 527 381 72 70 
2 120 Hz FWRS (fig . 2) 210 199 95 529 371 70 70 
2 120 Hz SCR (fig . 3) 210 202 96 543 378 70 70 
2 1 kHz SW (fig. 4) 210 194 92 543 363 67 70 
3 Constant current (fig . 1) 210 197 97 525 366 70 70 
3 120 Hz FWRS (fig . 2) 210 200 95 545 372 68 70 
3 120 Hz SCR (fig . 3) 210 199 95 561 370 66 70 
3 1 kHz SW (fig . 4) 210 196 93 544 364 67 70 
1. Total amp-hrs into cell at charge . 
2 . Total amp-hrs out of cell at discharge . 
3 . Total watt-hrs into cel l at charge . 
4. Total watt-hrs out of cell at discharge . 
5. Temperature of cell electrolyte at start of charge. 
6 . Temperature of cell electrolyte at end of charge. 
6 
-------
T5 1 
T6 
2 
(OF) (0 F) 
-- 104 
72 100 
76 111 
73 107 
73 98 
73 102 
-- 107 
-- 110 
f--
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cr 
400 
cr Vl 
G E 200 
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400 
200 
0 
4 8 12 16 
CHARGE TIME, sec, x103 
18 
Figure 1. - Charge cu rren t as a function of charge time for 
constant current cha rger. 
4 8 12 16 20 
CHARGE TIME, sec, xl03 
Figure 2. - Charge current as a function of cha rge time 
for 120 Hz full wave rectified sinusoidal charger. 
400 
200 
0 4 8 12 16 20 
CHARGE TIME. sec, x1Q3 
Figure 3. - Charge current as a function of charge time 
for a 120 Hz sil icon controlled rectified cha rge r. 
400-
f--
~ - -~ 
~V> 
=>0.. 
U E 200-
L.U '" t.:> 
~ 
« 
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u 
o 123 
CHARGE TIME, sec, x 103 
Figure 4. - Charge current as a function of 
I 
4 
c ha rge ti me for 1 k Hz sq ua re wave cha rge r. 
CHARGE METHOD 
CONSTANT CURRENT 
120 Hz FULL WAVE 
RECTIFIED 
120 Hz SILICON CON -
TROLLED RECTIFIED 
POOLED STANDARD 
DEVIATION 95% 
CONFIDENCE INTERVAL 
1 k Hz SQUARE WAV E ~ 
60 70 
ENERGY EFFICIENCY 
80 
Figure 5. - Average energy efficiency for charge methods. 
_ __ ---1 
~. 
-
]2. Governmen t Accessoon No . 
--- - . - - -- -
I . Report No . 3 . ReC IpIen t 's Ca taloy No 
NASA TM-82709 
._-
- - - -1---'--
4. T,tle and Subti tl e 5. Repo rt Date 
EFFECT OF POSITIVE PULSE CHARGE WAVEFORMS ON THE September 1981 
ENERGY EFFICIENCY OF LEAD-ACID TRACTION CELLS 6. Perfo rm ing Orga nil atlOn Code 
778-36-06 
7. Author!s) B. Performing Organ iza tion Report No . 
John J. Smithrick E-991 
10. Work Unit No . 
9. Performing Organ izat ion Name and Address 
National Aeronautics and Space Administration 
Lewis Research Center 
11 . Contrac t o r Grant No . 
Cle veland, Ohio 44135 
13. Type 01 Report and Per iod Covered 
t 2. Spo nsori ng Agency Name and Address Technical Memorandum 
U. S. Department of Energy 
14. Sponsoring Agency ~Report No . Office 0 f Vehicle and Engine R&D 
Washington D.C. 20545 DOE!NASA!51 044- 22 
15. Supplementary Notes 
Final report . Prepared under Interagency Agreement DE-AI01-77CS51044. 
16. Abstract 
The effects of four different charge methods on the energy conversion efficiency of 300 ampere-
hour l ead-acid traction cells were investigated. Three of the methods were positive pulse charge 
waveforms; the fourth, a constant current method, was used as a baseline of comparison . The 
positive pulse charge waveforms were; 120 Hz full wave rectified sinusoidal (FWRS), 120 Hz 
silicon controlled rectified (SCR); and 1 kHz square wave (SW). The constant current charger 
was set at the time average pulse current of each pulse waveform, which was 150 amps. The 
energy efficiency does· not include charger losses. The lead-acid traction cells were charged to 
70 percent of rated ampere-hour capacity in each case. The results of charging the cells using 
the three different pulse charge waveforms indicate there was no significant difference in energy 
conversion efficiency when compared to constant current charging at the time average pulse cur-
rent value. 
17. Key Words (Suggested by Author(sli lB . Distribution Statement 
Batteries Unclassified - unlimited 
Charges STAR Category 44 
Electric vehicl es DOE Category UC-96 
Electrochemistry 
19. Securit y Classil . (01 this repor t) 20. Secur ity Classil . (01 this page) 21 . No . 0 1 Pages 22 . Price 
Unclassified Un classified. 
. For sale by the National Technical Information Service , Spri ngfie ld. Virginia 22161 


Effect of positive pulse charge waveforms on the energy efficiency of lead-acid traction cells

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