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UNIVERSITY OF ILLINOIS
LIBRARY
Class Book Volume
Je 07-lOM
f
4- f
,„1f-^ ;>i^-.. ,. 1^:
i t -f- --i-
I
TESTOF
A ZINC LEAD STORAGE BATTERY
CHARLES HUGH BETHEL
THESIS
FOR
DEGREE OF BACHELOR OF SCIENCE
IN
ELECTRICAL ENGINEERING
COLLEGE OF ENGINEERING
UNIVERSITY OF ILLINOIS
PRESENTED JUNE, 1907
^1
t
UNIVERSITY OF ILLINOIS
liay 28 , i9o7
THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY
CHARLES HUGH BETHEL
ENTITLED TE.S.T .O.F...,.A Z.IllCr.LEAD STORAGE BATTERY
IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE DEGREE
OF BACHELOR OF SCIENCE IE ELECTRICAL ENCINEERINQ..
6....<A»r««<w...
HEAD OF DEPARTMENT OF ELEGTRICAL ENGINEERING
1 jle^56
Contents
.
Page
Introduction
Description of Cells 1«
' Treatment of Cells 4.
Tests 5.
Sumraarj'' of Tests 31.
Discussion of Tests 3S.
Conclusion 55.
Digitized by the Internet Archive
in 2013
http://archive.org/details/testofzincleadstOObeth
Introduction.
The lead storago battery lias been inve'stiga^ted loy many
obser\,'-erH and data are a,vailable in najciy exhaustive ^Torks. Ir con-
trast with this is the singular lack of published matter on bimetal-
lic accumulators. In vie^ of this an attempt was made to obtain
for comparative tests, cells of iron-nickel or Edison, zi^ic-copper
or Philips-Entz and lead-zinc storage batteries. It was possible
to obtain only the latter. Two BO-ampere hour lead-zinc cells were
obtained from the United States ntorage Company of New Rochelle,
N.Y., for testing.
A
Description of Cells.
The batteries tested were two lead-zinc storage cells.
No. 6, of the United States Storage Battery Company's make. The
following table gives the dimensions and rates of the cell as giv-
en by the makers and also the weight of the parts.
Discharge for 5 hours at 12 amperes
" " 8 at 9
10 at 8
Normal Charging Rate -• 9 amperes.
(^idth 8 3/4 inches{
Outside Dimensions (Length 11 1/2 "
(
(Height 8 •»
Weight of Cell complete 36 pounds
Weight of Positive Element 14.3 "
•* of Negative " 3.93 "
(Zinc .48 pounds(
(Connector 1.45(
(Mercury 2.00 3.93
Glass Jar, Glass Supports & Cover 11,2
Electrolyte 10.0 ft
Posit ive Element :-
The positive element consists of six lead units burned
to an antimonious lead grid. Each unit is composed of a number of
a number of perforated lead plates riveted between two antimonious
lead plates with antimonious lead rivets and with an antimonious
lead post cast in the center. The unit is S** X 3" X 1" and is
burned to the grid by means of the post so as to be in a horizon-
tal position. The whole element is supported on four glass sup-
ports like pieces l** long from a angle iron. Lead perioxide
is formed, not pasted, on the lead plates.
Negative Element :-
The negative element consists of spongy zinc amalgam in
the bottom of the cell. Connection is made to the zinc amalgam by
means of copper rods which lie in grooves in the bottom of the jar
and extend up one side to a lead bar. Above the zinc the copper
rods are insulated. When the cell is discharged, the negative con-
sists mainly of mercury, the zinc having passed into solution.
Elect rolyte:-
When the cell is fully charged the electrolyte is sul-
phuric acid of 1.20 specific gravity and when the cell is dischar-
ged, there is a heavy solution of zinc sulphate in the bottom and
sulphuric acid above.
The cell in nowise resembles the ordinary plate form of
storage battery but in arrangement of parts is more like a crow-
foot or gravity battery. This form of construction, whilte it el-
imates buckling and prevents any particles getting from the nega-
tive onto the positive, results in a high internal resistance.
The use of the mercury prevents local action on the zinc which has
J.
been one of the serious drawbacks to the use of zinc in storage
batteries
,
Cell, dincliar,'T,ed
.
1
\
I
I
Positive element, negative connector
and glass supports.
I
Treatment of Cells.
The cells were received December 20th and set up January
10th. The zinc was in strips 2'' X 4'* X l/32'' and the positives
partially charged, in setting up the cells, the mistake was made
of not thoroughly amalgamating the zinc and considerable was con-
sumed by local action at the beginning.
The cells were then charged and discharged a number of
times and had at first only a small capacity. It was some time be-
fore the zinc sponge built up t o any great extent. Several over-
charges were given the cells. They were then allowed to stand
with an occasional small discharge and charge for six weeks.
Before beginning the tests the cells were given an over-
charge, a discharge and charge. The five hour tests were the first
made
.
s
Tests.
Test No. 1:- Capacity and efficiency test at twelve am-
peres discharging and nine amperes charging.
Test No. 2:- Capacity and efficiency test at nine am-
peres discharging and charging.
Test No. 3:- Variation of specific gravity with condi-
tion of cell.
Test No. 4:» Capacity and efficiency test at eight am-
peres discharging and nine amperes charging.
Test No. 5:- Capacity and efficiency test at 19.2 am-
peres discharging and nine amperes charging.
Test No. 6:- Capacity and efficiency test at 36 amperes
discharging and nine amperes charging.
Test No. 7;- Capacity and efficiency test at nine am-
peres discharging and charging at 60** centigrade.
Test No, 8:- Short circuit test of Cell No. 2.
Tests Nos. 1, 2, 4, 5, 6 and 7 were run in a similar man-
ner. The connections were made as in Figure 1.
1
6 o 6
oV
I
Fig. I.
6.
The voltmeter leads were taken directly to the plates of each cell,
thus eliminating any I-R drops in contacts or leads. The current
i both on charge and discharge was sent through the lamp bank and ad-
justing resistance as in this way much closer adjustment and stead-
ier current were obtained. The slight variations in current, due
' to fluctuating line voltage, were ignored as it was felt that they
would practically compensate each other but in getting closed cir-
cuit readings, close adjustment of current was always made.
The tests were begun by bringing the battery up to full
gasing charge at the normal rate and readings of closed and open
Icircuit voltage was taken as soon after the circuit was opened as
the voltmeter needle came to rest. The object in getting such a
voltage was to obtain something akin to the ohmic resistance of
the cell. The fairly consistent results indicate that this meth-
od is not without merit. The discharge was then started and the
same readings of voltage were taken at the beginning and at thei
end of five, ten, fifteen and thirty minutes and every half hour
thereafter. In some of the tests it was necessary to take read-
ings more often. The charge was made in the same way. The time
to stop discharge was a difficult thing to determine. On account
of the high internal resistance, it is hardly fair to apply the
same limiting voltage at the higher as at the lower rates of dis-
\
charge. Some idea about the condition of the battery may be had
from the amount of zinc in the cell but this does not give an ac-
curate method of determining the proper time to stop the discharge.
The makers state that the discharge should be stopped at two volts
but if this rule were strictly adhered to these cells would give
7.
but a fraction of their possible capacity. Running until the open
circuit voltage had reached about 2.33 to 2.36 would perhaps have
been the most satisfactory method. To determine the time at which
the cells had become as fully charged as at the beginning of dis-
charge was about as difficult as t o determine the proper point to
end the discharge. There is no well defined maximum voltage to
which the charging cell rises as in the lead storage battery. Of
course, it is possible to tell when the positive element has become
fully charged by the free evolution of gas but there always re-
mains the question if as much zinc has been deposited during charge
as was consumed during discharge. The negative element never gases
freely as does the positive.
These points were practically guessed at on account of
the lack of definite information.
For Test No. 3 t he cells were discharged and a measure
of the discharge made. After each five ampere hours had been re-
moved, the elect olyte was stirred and the density and temperature
taken.
For Test No. 7 one of the cells only was used. It was
placed in a tub of water which was made into a water rheostat. By
heating the water, the cell was raised to 65*> centigrade and the
voltage and temperature noted at frequent intervals. During this
part of the test, the cell was discharged about ten ampere hours
from full charge. The cell was then fully charged and a regular
capacity and efficiency test at nine amperes discharging and charg-
ing made. During this test the temperature of the cell was main-
tained as near 60' centigrade as possible.
?or Test No. 8 one of the cells was short circuited
through a large ammeter and readings of current taken every thirt
seconds for five minutes. The recovery of the cell from polari-
zation was then observed.
9.
Test No. 1:- Discharge at 12 amperes and Charge at 9 amperes.
This capacity and efficiency test was the first one made.
The cells had been slightly overcharged and then discharged at 12
amperes and recharged just before this test.
The cells were discharged at 12 amperes through a rheo-
stat but such variations in current occurred that the method of
discharging with the lamp bank in series across the line was re-
sorted to in later tests. Immediately after the end of discharge
the cells were charged at 9 amperes.
The poor regulation of current on discharge v/hich may
have resulted in a somewhat lower average rate of discharge than
12 amperes may account for the high ampere hour efficiency.
Though the cells fell below the limit of two volts per
cell, the full rated capacity of 60 ampere hours was taken out.
10.
Time L\rcuitClosed
CtrcoitOpen
AppoveiivRe5i5tqiice Re ma yks
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Ampere Hours Output •
Ampere Hours Input -
Atnpete Hour EfficiencyWatt Hour-^ Output ~
Watt tiour^s Input ~ ~
Wott hour Eff/c/encyVo ft Effi c /ency
- 60,0e5~x
- 3Z.0%- IZ5,I
181.1
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12,
Test No. 2:- Discharge and Charge at 9 Amperes.
This capacity and efficiency test at 9 ampere rate was
made five days after Test No. 1. At the beginning the cells were
given a good gasing charge.
The cells were rated to give 72 ampere hours at this rate
but when 67 1/2 had been removed the voltage fell so low that the
test was stopped.
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13.
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/5.
Test No. 3:- Variation in Specific Gravity of the Electrolyte with
Amount of Charge.
Cell No. 2 was filled to the usual height with distilled
water and 60 ampere hours discharged at 15 and 10 amperes. After
each five ampere hours of discharge, the electrolyte was stirred
and the specific gravity measured by means of a syringe hydrometer
and the temperature taken.
Prom considerations of the chemical actions in the cell,
the specific gravity should slightly decrease on discharge. Assum-
ing no change in volume of the electrolyte, the net result of dis-
charging the cell is to take from the cell one ion of sulphuric
acid S 0^ (weight 96 atoms of hydrogen) for each atom of zinc
(weight 65 atoms of hydrogen. i The action, however, may not be
as simple as this and instead of the lead peroxide being changed
to lead sulphate, it m.ay be simply reduced to lead and water form-
ed, in which case the net result would be the addition of zinc
to the solution and an increase in the specific gravity would in-
crease slightly. In any case, however, the change should be very
small, as there is less than 1/2 pound of zinc t 10 pounds of acid.
The action in the cell when undisturbed on discharge is
to have formed at the bottom a heavy solution of zinc sulphate and
to have a dilution of the solution at the top. On discharge the
solution at the bottom sometimes becomes so concentrated that zinc
sulphate is thrown down as a white precipitate.
Any change in density shown by the data may easily have
resulted from imperfect manipulat ion,.
16.
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tancc
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n.
Test No. 4:- Discharge at 8 Amperes and Charge at 9 Amperes.
This capacity and efficiency test at 8 amperes discharg-
ing and 9 amperes charging was made a week after Test No. 3. Just
before the test the cells were given a large overcharge at a low
rat e
.
The cells were rated to give 80 ampere hours and easily
gave full capacity. Cell No. 2 was in especially good condition
and judging from the amount of zinc and the voltage, the cell wouldli
have given considerably more than rated capacity.
I
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Watt Hours Input - - ZSSOWott Hour E/^:f tcfency - 77. I %Volt E/:7lc/ency - - ~ 30,1 %
la
Test No. 5:- Discharge at 19.2 Amperes and Charge at 9 Amperes.
This capacity and efficiency test at 19.2 amperes dis-
charging and 9 amperes charging was made five days after Test No.
4. The cells v/ere given a small overcharge just before the test
began
.
The cells were not rated at as high a rate as this but
the duty of storage batteries under some conditions is t o safeguard
against breakdowns and under such conditions are likely t o be dis-
charged at high rates.
Though the voltage fell off rapidly and the capacity was
small, the cells showed that they would be of use at this rate.
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4 • 44 Z60 Z-81 Z^4 Z64 .0161 ,0/18
>f ; ^4 Z6I ISt^ IGG Z6C .0/66 .0163 30.3
o> 44 1
'
I3z Z(o7 ZU .0156 .0183 y^ /\
6-74 ^6^S ZS^ Zlo3 tio .0161 .0/67O XI x»7)0.0
x ^ /I /I
6 Zdl ^83 Z.14 Z-7S ,0/4j- ,0144y\ -J60-3
b 1 J Z63 Z.^l 1,1 Z-7G .0/60 .0/66 ^1 Ay30Z7,74 Zdi i9Z ZIQ zis .0144 .0166 3a 3
7.' ^4 Z9Z .0144 .0144 30.3 Chayge Bhded
too? lOlB OZOG .OZOO A Ve. an PISCha i^^e
1663 .0/19 .0/6^ A ye. Oh Cha \rge
Ampeh-e Hours Output - J(5-
^
Amp&re Hours Input ~ ' 1-^
Ampere Hour Efficiency - 31.5 %Watt Hours Output - - 77JWott Hours Input - ' '119.0
Wait Hour Efficiency - " 6S.0 7^
Volt Efficiency 7/ 7o
Test No. 6:- Discharge at 36 Amperes and Charge at 9 Amperes.
This capacity and efficiency test at 36 amperes discharg-
ing and 9 amperes charging was made immediately after the comple-
tion of Test No. 5.
No rating was given the cells at this rate of discharge
but lead storage batteries are rated at four times the normal
charging rate for one hour and these cells were given a similar
test. The time to stop the discharge was judged by the open cir-
cuit voltage.
The rate was evidently too high for the cells though
no injury was apparent. The voltage fell off so rapidly that the
use of the cells under such conditions would be very unsatisfac-
tory. It is probable that the low ampere hour efficiency was due
to error in judging the time of complete charge.
Time
\)
/EMr
Circu itClosecl
EMFCi^^co it-
Open
Apparent
R, Rz
v:>^
^
Remai'ks
1 IddPM Z 00 zoo O i ^Ohci i^g& Sega
n
•1 94 I-3S- Z44- ZH .0139 013^ 3/
7-4^ '• ids 187 Z4I Z4Z .6IS3
7' 47 1 < 180 I-8Z Z4I .0/6$ ,6/63
7:S7 1 • I-7S 177 Z3^ Z39 .on8 3>ZS
e: 7 1-66 US Z37 Z37 ,0180 ,0180
8:1^ *<1 G4 Z.37 Z37 ,om .ozo^
6:17 < 1 / 60 7- GO Z.3G Zdh O'Zli ,oZI1 Q/schay'ge En tied
8 • s tGG Zfl Z47 .ozn ,OZIl Cha Ki7^ on
Z7f Z77 ZSf zs^ .ozse 34-/)
Z7? zdo ZS7 ZS7 .OZ^Z
8:S-/ •• Z.76 zse 2S3 .out M44 33P
d:ZI 1 f Z-78 Z 6/ ,0118 .om ZZ O
3:S/ 27S t&l ZG4 .0(61 ,0189 3/Q/o :z( r r Zbl Z8f Zb(o ZGG .0161 ozoo ZZO
• 1 Z8^ Z87 Z6S .0161 .0118 31 9
11 \ZI 1 » tS9 ZBZ Z77 .om .OlSl 31 3
II '.:5i • Z30 ZS3 Zll Z78 .on 8 d/9
II ''41 f 1 Z3I ze3 Z78 Z.7B ,6l'6l 3/9II ' SI "1 zei Z93 Z78 Z7S ,0IH .0IS6 319
IZ:ol 1 • ZS3 Z76 Z13 .om .diss 313
mi mi t^$4 ,0/78 .0176 AvP.on Disrhar^^
Z661 Z^b6 .OlhS mo Ave. on Cha r^<e
Ampey^e Hours Output - - Z€AAmpet^c /iours Input - ~ ^0,0
Ampeire h o u r ff/cien cy - 88-0 Va
Watt Hour^ Output ~ - 46^Wait HOUR'S Input - - ~ QS-^\A/at7t hou\r Efficiency ' ' 54-^%Vo/t E ffi cien cy 6/. 7%
Test No. 7:- Discharge at 9 Amperes and Charge at 9 Amperes. Cell
Maintained at 60" Centigrade, (140** Pahr .
)
This capacity and efficiency test at 9 amperes was made
with the cell at 60** centigrade with the object of determining as
far as possible the effect of high temperature.
A comparison of the results of this test with those of
No. 2 is shown in the following table of averages:-
E. M. ?. E. M. P. ApparentTemperature Circuit Closed Circuit Open Resistance
30** 2.145 2.400 .0285 ( Cell( Discharging
60** 2.189 2.402 , .0237 (
30** 2.858 2.721 .0152 ( Cell( Charging
60** 2.796 2.611 .0206 (
These results when compared with the effects of a rise
in temperature on a lead cell indicate that there was less polar-
ization at the high temperature, due to a more active positive el-
ement .
The fact that the apparent resistance was lower on dis-
charge and higher on charge at the high temperature is apparently
inconsistent but it must be remembered that this is not true re-
sistance. It is probable that the true resistance was lowered by
increased temperature.
7~/ ni e tuve i7
Top Ce-nt
Te frt pera-
tio-t V oin
E M F F^e ima ^ks
7:43-AM %4 3 Ce// /ackec/ /O Ofnp.
3 :oo Z9 7 Z9A h i^- <py- ±ull CharQe
8: /o -d 6 d6S ; /6 40 z. rzr3 : ^7 4-S 6 ^ rzaid? 6~/
8 : SS-'O z.rz8 ' vT^ 60-0 60/S : 03 6^ S zsz Ih-solatfoh a-f- neg
a//<?cti6'c/ by hcot.
/
27
EM FC\Ycu itCIo^ed
EMFC\YCOI tOpen
Apposeht/ c 1 r?pC- Y ~
oiyore
10 :tOAM z sz e .0/33 ss DIsc ha \rQe Beqan10 ; t 36 Z4-e> ••
10 :d6~ Zds~ Z4-7 • .0/33 6/s10 ; so Z.4b •
•
.0/44
// : ^0 Zdo Z ^4S •• .01^6
II ; so zz&s- •• ,0/7J
iZiiopM Z Z3 Z4-dS .0/73
It ' 40 zz^r It .018^ SS8it- so ii .0139 6-/^-7
1 : Zo Zt4 Z4t (i ,OZoo sg. h
1 : SO Z-4Z •« .oz/i 6-3zZIBS- %40 f r .0Z34 Gz d
ZlSo Z IG Zdd G/.8
Jior Z- 14 ZdSS 1 1 .0U7j:zo ZI3 2d8 • Uc?
3!dS Z IIC «
.6Z94 (^0.8
J ISO z ZJ7 1 ft .03a ^0-6
i:oS ZJ6S 03/7
Z 07 Z J6 •• 03ZZ ^/^4:3S ZO^ Zd4 .0333
Zo/s Z-^dS J3S(, Gl.6 '3pon<7e Consi/tnnd
.
4 1 SI Z-00 Z 33 •i ,03^7 bo-s- DiSO ho i^c/e Fnded.
4:sd Z73 Z S^ .0U4- Choi^QC Begun.
ZS4 .0Zd3
s: 1 3 ^•77 ^.S3 ./)ZS4> SOBs:ts Z17 z •• SQOS'.SQ 113 zs^ .0Z44- S-8&g:z8 2 8Z %S1 1 .0Z44 G/0(o'.SS Z-84 ZS6 1 r
.0Z39 S<8
7!Z8 Z8^ . ozb'C SB'S-
I'Sd Z 8Z. Z60 .0Z44
Z 60 Z ^0 ' < SS86iS6 Z7SS Z 60 Go./
B8.
Tim e
E MF
c losed
J— AW f~~
Civco it
OpenB
Cuvt^ent4ppo rent
H
Teenpey-
3 :Z8 PM Z GO 3 • 0/34
3:S8 Z77S % 6IS- .6173 S8Jzn^ .01 7t SS 4
10 : SB Z78 ' * .0/67 60/II :Z^8 Z7S / 63 1 0167 60-S^
II / SB Z79 • \ .0167
IZ:Z8 Z80 •» 6o3f%\S8 Z8I «i .0/4"^ S-G-Z.
J : Z8 Z7/ 1
1
Chci vg^e Comp/ete
1: 40 .0/33Z.I 63 Z40Z .0Z37
Z6li ,OZ06
Ampere Mour^ Output - 63 6Ampere Hours Inp ut ' ' ~76 -5'
Ampere Hour E ///'c/ency76.0 Va^
Wat/^ Mourns Outp ut - -/30.S\
Wait Hours Input - - eid-3
Wott Hou r £f/'/c/ency - 61 oy^\
Volt Efficiency - - - 16^^7o\
Test No. 8:- Short Circuit Test of Cell No. 2.
Cell No. 2 was fully charged and short circuited through
an ammeter for five minutes. There was appreciable drop in the
leads and ammeter as shown by the voltmeter attached to the ele-
ments directly. The current was noted every thirty seconds for
five minutes and the terminal voltage several times. At the end
of five minutes the circuit was opened and the voltage read im-
mediately and at the end of thirty and sixty seconds.
The cell suffered no apparent ill effects from this
rough treatment. The amount of current was not far from what could
have been predicted by dividing the voltage by the apparent resist-
ance.
JO
Elapsed EM rC{ \rC u it-
Closed
C~ A-? C~t- 1 1 r
Ci rcu 1 1-
Ope ii
(5 ; 00 113 Z. 70 QwcUit:' Closed
; / / 6 S/ ; II % o,a /
1 : dO /OOZ \
6 ISJ :
^^'^ 64-0 0-7S
634 : 004:^0 30.-5- 0.11^:oo 33.9 Circuit Opened
G' oo ^. f 7
J/.
Sunrniai-y of Tests.
The result n of these tests are partially su^^raarizecl in
the following curve sheets,
Plate IX shows the discharge curves at the various
rates. From, it a fair idea may be had, of what is to be expected
of the battery.
Plate X shows the variation of apparent resistance on
discharp,e with the condition of the cell. It shows that the
internal resistance depends more upon the amount of charge than
upon the rate of discharge.
Plate X shows the variation of volt efficiency and
capacitjj with the rate of discharge. The data on capacity are
not conclusive.
EUGENE DIETZGEN CO., CHICAGO.
Discussion of Tests.
The makers called attantion to the fact that this type
of storage battery has a higher efficiency and gives more satis-
factory service on low rates. On account of the long duration of
tests at low rates and the fact that the work was performed by one
man, no test was made at lower than the 8 ampere rate. Only one
test was made at each rate and this even under the best conditions
is unsatisfactory as a basis for judging the cells.
In view of the fact that it requires 185 ampere hours
to deposit 220 grams of zinc, the amount in each cell, the fail-
ure of the supply of zinc after 40 or 50 ampere hours* discharge
would seem to indicate either that the ampere hour efficiency of
the zinc electrode v/as low or that there was some local action.
The highest capacity shown by the cell was on the 8 ampere dis-
charge and previous to that test the cells had been given a long
slow overcharge. Some of the tests made after the cells had stood
for a time showed a small capacity in the negative element despite
the fact that the cells were charged at the normal rate until they
I
gased freely from the positive plate. This would lead to a sus-
picion of local action. Some tests to determine the amount of lo-
cal action would be instructive.
The only method used to determine the resistance of the
I
cells was the one described of taking the voltage with the current
;
flowing and opening the circuit, reading the open-circuit voltage
I
as soon after opening the circuit as possible, then dividing the
the difference of those two readings by the current. This method
is not very satisfactory and the results are not altogether con-
sistent. Much of the effects of polarization enter into the data.
An attempt was made to determine the internal ohraic re-
sistance by a method given by Lyndon in his '•Storage Battery En-
gineering," Page 183. Connections were made as in "Pigure 2:-
E was a source of alternating current of 60 to 150 frequency. B
was the battery whose resistance was t o be measured. X was a piece
of No. 14 German- silver wire about e** long. MN was a No. 2 5 Ger-
man-silver bridge wire 200 centimeters long. C was a condenser of
several M. ?. and R a telephone receiver. The connections are
simply those of an ordinary Wheat st on bridge.
Difficulty was encountered in finding a balance for K
on the wire. The cell was carefully insulated and two cells were
connected in opposition but it was impossible to locate a point on
MN at which no sound in R was audible and the minimum could not be
located with any certainty within ten centimeters. With a piece
of German-silver wire substituted for the cell, almost a perfect
balance would be obtained. The point on MN of zero sound could be
located within one-half centimeter.
No other methods of determining the resistance were
tried.
Only one test at any other temperature than 30** centi-
grade was attempted, one at 60*. Prom it some interesting things
developed but they would have been much more conclusive could sev-
eral tests have been made at that temperature. A more important
test would have be«n one at 5* or 10® centigrade as batteries in
signalling and such work are likely to meet such conditions.
The short circuit test showed the ruggedness of the con-
struction of the cells though they would fare better under such
conditions than the lead storage battery on account of higher in-
ternal resistance. Such an accident apparently cannot cause buck-
ling or other immediate serious injury to the cell.
These are by no means complete tests of this storage bat-
tery, as it is probable that no tests of storage batteries are com-
plete until a life record has been made. On account of the diffi-
culties encountered in determining the points of complete charge,
the tests are not conclusive as t o ampere hour efficiency. They
do, however, give a good idea of the volt efficiency and a fairly
good idea of what the cell will do at the different rates.
Conclusion.
This lead-zinc storage battery is somewhat lighter than
the ordinary stationary types of like capacity, weighing 36 pounds
to from 48 to 63 pounds as given by various makers for 80 ampere-
hour cells. The comparison on a watt -hour basis is even more fav-
orable, owing to the high voltage. On the 8 ampere discharge,
this cell gave 5.04 watt hours per pound of cell while lead stor-
age batteries give from 2.4 to 3.2 watt hours per pound.
The uses of this battery are probably confined to such
things as telegraphy, fire alarm signaling, block signaling, gas
engine ignition, cautery and similar purposes. Its high internal
resistance renders it unfit for central energy telephone uses.
It might find a place in the small isolated lighting plant where
the generator is run occasionally to charge the battery which then
carries the load at a low rate.
The high internal resistance of this battery and conse-
quent low efficiency on high rates of discharge are its character-
istics. However, for some purposes this type of cell has a few de-
cided advantages. The fact that the state of charge can be told
approximately by mere inspection and the ability of the cell to
withstand such rough usage as short circuiting should recommend
it for use where inexperienced men must handle it
.
4 -+
.* - ^
* - * -4-
--4 .4-
