LOW WATER LOSS BATTERY
BACKGROUND OF THE INVENTION
I. Field of the Invention
The invention relates in general to lead-acid storage batteries, and, more
particularly, to a low water loss battery with improved reduction in the rate of
water loss.
II. Description of the Prior Art
In automobile industry, the battery grid is formed of a lead-based alloy. Pb-
Ca-Sn alloy is used for the negative electrode of a lead-acid battery. However,
using said alloy for the positive grid of the battery makes the battery very
sensitive and reduces the cycling ability. In heavy-duty applications, it poses a
problem. To provide battery grids with sufficient mechanical strength and
hardness, as well as with longer cycle life by causing improved electrical
conductivity, a lead-antimony alloy containing from about 1 to 2% by weight of
antimony has been used for the preparation of positive grid for lead-acid
batteries. The antimony also improves the corrosion resistance of the positive
plate against acid attack, and increases the ability of the battery for recovery
from deep discharge cycles.
During the cycling of conventional batteries, which use antimony alloy grids,
the decline of the voltage at the end of a recharge is recorded with
progressing cycle life. The voltage decrease occurs mainly during the
overcharge part of the recharge, that is, when only the gassing reactions are
involved. It has been found that primarily the hydrogen evolution at the
negative electrode that becomes facilitated and the reaction takes place at a
lower voltage level. The reason for this behavior is that in the event of
corrosion of the grid of hybrid batteries, the antimony comes out while
charging. Due to corrosion, antimony releases from the alloy as antimony-
(+V)-ions and is mostly adsorbed at the lead dioxide inside the positive
electrode. Some of the antimony (+V)- ions diffuse through the separator,
used as a distance-keeping component between the positive and the negative
electrodes, and get into contact with the negative electrode, where they are
reduced to antimony-(+III)-ions, and are also finally reduced to metallic
antimony. On subsequent charging, antimony gets deposited on the negative
electrode, that is, the antimony plates out onto the negative electrode. This
metallic antimony deposition is considered to be "poisonous", because, it
allows for evolution of gaseous hydrogen to proceed more easily than what is
achieved from pure lead, and consequently, such phenomenon results in the
loss of water. It also facilitates the hydrogen evolution with all subsequent
negative effects. Excess charge develops into electrolysis of water. The
process of electrolysis starts prematurely, even at normal charging voltage.
Thus, the major problem with the use of lead-antimony alloys in grids has
been the transfer of the antimony to the negative plate during cycling where it
increases the rate of gassing. Facilitated hydrogen evolution means a lower
charging efficiency, resulting in higher water consumption, increased battery
temperature and reduced shell life.
Conventional automotive batteries using lead-antimony grids typically
containing up to 4.5% by weight of antimony, show a relatively high
magnitude of float current at the completion of charging. The electrode plates
in a maintenance-free battery, ideally, should accept only a small current
during constant voltage overcharge so that only minimum gas generation
occurs with the accompanying water loss being minimized.
It would be desirable to reduce the amount of antimony in the positive grid
alloy in order to reduce antimony poisoning and to improve the end-of-charge
voltage characteristics. Using lead-calcium-tin alloy for the positive grid helps
to make for water loss, but, in such cases, the battery becomes very sensitive,
cycling ability comes down, and in heavy-duty applications, it poses a
problem. Lead-calcium alloys containing traces of arsenic, selenium, tellurium
or manganese and tin exhibit good cycling capabilities, but cause an increase
in current and consequently result in an increase in water loss.
Antimony alloys, on the other hand, give good cycling duty. Hence, substantial
advantages being achieved from lead-antimony alloys in positive grids, there
should be some technical solution for counteracting the undesirable effect of
antimony "poisoning", to yield a "foolproof result
Studies have shown that antimony does not deposit uniformly on the negative
grid surface. Rather, it deposits in the form of clusters or peaks. It is also
found that the hydrogen evolution rate and the amount of antimony are
proportional. Antimony, which grows as dendrites or whiskers, allows for easy
hydrogen generation at the tip of the dendrites. It has, therefore, been
observed that the antimony dendrites cause higher degree of water loss.
Several ideas have been proposed in an attempt to overcome the aforesaid
difficulty/ problem. Prior art teachings on low water loss technologies suggest
that various battery separator types retard the antimony poisoning of the
negative plate and thereby reduce the hydrogen evolution and, consequently,
water loss of lead acid batteries. The basic principle is that organic molecules
released from the separator are adsorbed on the antimony sites of the
negative electrode and thereby inhibit the catalytic effect of the antimony on
the hydrogen evolution [W. Boehnstedt, Journal of Power Sources (1993)
211-220].
It is well known that the effects of antimony poisoning can be retarded by the
use of rubber (natural rubber being a cis- 1,4-polyisoprene) separators. This is
caused due to a chemical interaction, whereby, in the presence of extracts
from rubber separators, antimony is deposited on the negative electrode in a
different modification, which is relatively less poisonous, and which in a way,
reduces the hydrogen evolution reaction. This results in comparatively less
total antimony deposition. However, rubber separators are quite brittle and
difficult to handle and also have other weak points.
In car batteries, cellulosic separators were the most commonly used battery
separators for decades. One of their advantages over other car battery
separators (e.g. sinter-PVC separators, glass fiber separators) is the
reduction of the battery water loss by retardation of the antimony poisoning
effect
Polyethylene separators, on the other hand, are superior to cellulosic
separators, in most of the aspects, and offer favorable property
characteristics, such as, minimized electrical resistance, low acid
displacement, high oxidation stability, excellent processability, excellent
mechanical properties, except lack of significant antimony poisoning
retardation. Because of the inherent limitations of cellulosic separators,
several approaches were tried in order to modify the polyethylene separators,
until a new polyethylene separator, provided with "chemical agent(s)", such as
water-soluble, non-ionic surfactants (said separators, so modified, being
hereinafter referred to as 'treated separator", and described, in detail,
hereinafter), was developed with similar effect with regard to antimony
poisoning retardation of cellulosic separators, while maintaining all other
superior performance properties of polyethylene separators. Antimony was
found to be deposited on the negative electrode in a far less dangerous form.
The afore-mentioned "treated separator" was found to exhibit the ability to
retard antimony transfer to the negative plates and to reduce the water loss to
the level of batteries assembled with cellulosic separators.
The aforesaid "treated separator" is made from filled polyolefins and is
provided with "chemical agent(s)", formed of one or more water soluble
surfactants, such as herein described. The surfactants used are non-ionic
surfactants, which consist of a non-polar and a polar part and are applied
either on the surfaces of the separators, or on the side of the separator turned
towards the negative electrode, or on the side turned towards the positive
electrode or on both the sides of the separator, or these can be added to the
mixture for the production of filled poly-olefin separators. Examples of said
surfactants, among others, are oleylaminooxethylate, stearylaminooxethylate,
tallow fatty aminoxethylate, coconut oil aminooxethylate, coconut oil acid
diethanol amidoxethylate, coconut oil acid monoethanol amidoxethylate,
dodecanedioic-acid-N,N-diethylamide, fatty alcohol oxethylate such as
decylalcohol oxethylate, octylalcohol-oxethylate, coconut oil alcohol
oxethylate, tailow fatty alcohol oxethylate, stearyl alcohol oxethylate and oleyi
alcohol oxethylate, oleic acid amideoxethyiate, fatty acid oxethylate such as
tallow fatty acid oxethylate and tall oil fatty acid oxethylate,
oxoalcohoioxethylate with 8 to 20 carbon atoms in the alcohol residue, fatty
acid glycerinesteroxethylate such as polyoxethylene glycerine monolaurate, -
stearate, oleate or palmitate and castor oil oxethylate as well as fatty acid
sorbitan ester oxethylate of the Tween type. The surfactant concentration
which is used, in reference to the accumulator electrolyte, is chosen to be
greater than 0.03 g/l, preferably greater than 0.08 g/l and in particular greater
than 0.16 g/I. In reference to the separator surface, the surfactant
concentration is chosen to be greater than 0.1 g/m2, preferably greater than
0.25 g/m2 and in particular greater than 0.5 g/m2.
The effect of said organic chemical compounds provided on the separator, as
surfactants, on the performance of the lead-acid battery was assessed by
means of a water-loss test, in which, automotive batteries were fully charged
before an overcharge at a constant voltage of 14.4 V, started for several
weeks. The current was recorded, as shown in Fig. 1 of the accompanying
drawings, which illustrates a graph showing the water loss test carried out on
a lead-acid battery having a "treated separator", when compared to a
standard polyethylene (PE) separator. The higher current level at the start is
due to residual lead conversion, that is, as compensation for some prior self-
discharge. The current increases slightly with time due to poisoning of the
negative plates by antimony or other elements that are more noble than lead.
In the case of lead-calcium alloys, traces of nickel, selenium, tellurium or
manganese and tin can cause an increase in current. When using the
aforesaid treated separator", made of porous polyethylene containing the
aforesaid "chemical agent(s)", the current flow was found to be reduced, as
illustrated by the lower curve in Fig. 1.
The weight loss that these batteries exhibit, due to decomposition of water by
electrolysis, is proportional to the total overcharge, that is, the integral of
current over time, in accordance with Faraday's law. The said "chemical
agent(s)", provided on/ in the "treated separator" cause(s) to reduce the water
loss to an extent of 30- 40%. However, this reduction is not good enough.
The details of the aforesaid "treated separator" have been provided in U.S.
Patent specification No. 5,246,798, which is mentioned herein by way of
reference.
Water loss reducing effect is also known to be caused by additives in the
battery. One such additive and its use for the purpose of minimizing water
dissipation in an electrolytic cell has been described in U.S. Patent
specification No. 3,928,066A. The additive used is a. quaternary ammonium
compound wherein there has been substituted for all the hydrogen atoms an
aliphatic and/or aromatic group. As a genera! reference, such or other
additives, described hereinafter, are denoted as "additive".
Zinc has been shown to be a beneficial element as "additive" in reducing the
float current of lead acid batteries. U.S. Patent No. 4,086,392 issued to Mao
and Rao, discloses that the addition of elemental zinc or a zinc affording
compound to Pb-Ca-Sn and Pb-Cd-Sb batteries in certain levels, diminishes
the required float current. Mao and Rao have shown that the addition of a
small amount of zinc to the electrolyte (for example, 6 grams of ZnS04.7H20
per battery) decreases the float current of SLI batteries by almost 50% when
floated at 51.60 C and 2.35 V. Addition of zinc to the electrolyte diminished
the required float current, and consequently the water consumption in voltage
regulated charging modes. In another example, zinc was added to the positive
and negative active material in an amount of 340 ppm. The float current at
51.60° C was reduced by 49% at the hgh float voltage of 2.76 V per cell.
Smaller amounts were less effective but still reduced the oxygen and
hydrogen evolution float currents.
Zinc has been shown to reduce gassing, and, thus, the zinc leached into the
electrolyte reduces gassing and enhances stability of the potentials. Zinc is
the only element other than bismuth, which is effective in reducing both the
positive and negative gassing currents. Based on the amount of zinc added to
the active material in the Mao and Rao work, the reduction in gassing currents
is achieved. Zinc stabilizes the plate potentials upon float and reduces the
effects of other impurities which might be present particularly on the negative
active material. Zinc can stabilize the potential of the active material, and
reduce the float currents, which cause gassing, and reduce water usage when
added to the active material in amounts of 350 ppm or more. The stabilized
currents permit improved recharge and ultimately higher capacity and longer
life. The addition of zinc as an additive can give the maintenance-free battery
a low water usage than that which could be attained with lead-calcium-tln
alloy grids. Zinc was believed to deposit on or plate out on the negative
electrodes during voltage regulated overcharge.
However, the above prior art approach of reducing the float currents in
batteries by addition of zinc and its compound(s) does not cover the normal
hybrid batteries (1.6% Sb, Positive electrode, and Pb-Ca, Negative electrode),
where its effect is minimal due to the morphology of antimony deposition on
the negative plate surface.
Water loss is a concern area in tropical countries. Life of lead-acid batteries in
tropical zones is appreciably lower than that obtained in the cold temperature
climates. In the tropical countries, the challenge is to make the battery last
under severe operating conditions which may include In addition to high
ambient temperatures, sluggish vehicle movement in the city centers, frequent
stops/ starts, rough road conditions, excessive running of the utility vehicles
and less dependable charging system. These operating conditions do entail
an element of cycling together with occasional deep discharges as well as
high propensity of positive grid corrosion.and more importantly, greater water
loss. This seems to be an area of genuine concern for those operating in the
tropical part of the world.
Despite the advances made in the art for dealing with the problem of reducing
the water loss in the batteries, there is a continued need to address the said
problem of further minimizing water loss in batteries, particularly for use in the
tropical climates.
The principal object of the present invention is to achieve a substantial
reduction in the rate of water loss in a battery of the type as herein described,
which had not yet been possible by adopting various means/ techniques, as
mentioned hereinbefore.
SUMMARY OF THE INVENTION
To achieve the object of the invention, it Is proposed to provide a low water
loss battery having a "treated separator" and an "additive" in conjunction with
the treated separator.
Accordingly, in one embodiment, the invention provides a low water loss
battery such as a lead-acid storage battery, with improved reduction in the
rate of water loss, characterized in that a separator, treated to retard antimony
poisioning of the negative plate is used, in conjunction with an additive in the
said battery.
Preferably, the separator used in the above low water loss battery is a
polyethylene separator containing "chemical agent(s)", e.g. water-soluble,
non-ionic surfactants, while the additive used in conjunction with the treated
separator is zinc and its compound(s), and in particular, zinc sulphate
ZnSO4.7H20.
According to the invention, the objects are achieved by the features of the low
water loss batery, as described hereinafter. Advantageous refinements of the
invention are specified in the following detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The above features of an embodiment of the present invention and their
relative advantages will be apparent to those having ordinary skill in the art
upon reading the following detailed description of the preferred embodiment of
the invention with reference to the accompanying drawings, in which :
Fig. 1 is a graph showing the float current for the water loss test carried out tin
a lead-acid battery having a "treated separator",, when compared to a
standard PE separator, according to prior art;
Figures 2A, 2B and 2C are graphs respectively showing the equilibrium float
currents of hybrid batter/ with "additive" only (Battery A), hybrid battery with
"treated separator" (Battery B) and hybrid battery with both "additive" and
"treated separator" according to an embodiment of the invention (Battery C),
when compared to a (reference) normal hybrid battery (X1), each of the
batteries being floated at a temperature of 60o C for a period of first 21 days ;
Figures 3A, 3B and 3C are graphs respectively showing the equilibrium float
currents of the aforesaid Battery A, Battery B and Battery C, when compared
to the (reference) normal hybrid battery (X1), each of the batteries being
floated at a temperature of 60o C, subsequently, for a period of second 21
days;
Fig. 4 is a graph comprising histograms showing the comparative water loss
characteristics of the aforesaid Battery A, Battery B and Battery C, with
reference to the (reference) normal hybrid battery (X1);
Figures 5A and 5B are graphs showing the relationships between water loss
and the "additive" concentration, in the Battery C, according to the present
invention, the battery being floated at a temperature of 60o C, for periods of
first 21 days and the following second 21 days, respectively ;
Fig. 6 is a graph showing the relationship between water loss and the
"additive" concentration, in the Battery C, according to the present invention,
the battery being floated at a temperature of 80o C;
Fig. 7 is a graph comprising histograms showing the comparative water loss
characteristics of the hybrid Battery C according to one embodiment of the
present invention, a lead-calcium battery (Y) with both "additive" and "treated
separator", according to another embodiment of the invention, as compared to
a (reference) norma! hybrid battery (X1); and
Fig. 8 is a graph comprising histograms showing the water loss characteristics
of a lead-calcium battery (Y) with both "additive" and "treated separator",
according to an embodiment of the present invention as compared to a
(reference) normal calcium battery (X2).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
To achieve the objective of the invention, a low water loss lead/ sulphuric acid
storage battery is disclosed. In the said embodiment of the low water loss
battery, according to the invention, a combination of a polyethylene separator
containing "chemical agent(s)" formed of one or more of water-soluble, non-
ionic surfactants (referred to as a "treated separator") and an "additive" in
conjunction with the treated separator are provided.
The nature of the "chemical agent(s)" of the "treated separator" has been
described in U.S. Patent No. 5,246,798, as mentioned hereinbefore. Provision
of the "chemical agent(s)", e.g. organic surfactant(s) on/ in the "treated
separator" effectively changes the morphology of antimony deposition on the
negative plate. It helps in Finer distribution by making the antimony distribution
more uniform by suppressing the antimony peaks [W. Boehnstedt, The
Battery Man, June 2005].
The "additive" which is used in conjunction with the "treated separator" is,
preferably, ZnSO4.7H20, which is known from the prior art described in the
U.S. Patent No. 4,086,392, as mentioned hereinbefore, and which is also
incorporated herein by reference. Although the effect of reducing the float
current by addition of zinc and its compound in a hybrid battery is minimal due
to the morphology of antimony deposition on the negative plate surface, but,
in presence of the treated separator", the morphology of antimony deposition
is appreciably altered and hence this additive becomes very effective. On the
contrary, common additives when used alone, are found to be less effective
due to the presence of antimony peaks.
Both the "treated separator" with the specific "chemical agent(s)", as
aforesaid, and the particular additive of ZnSO4.7H2O are known per se, and
further detailed explanations of these are therefore not necessary in view of
the disclosures made in U.S. Patent specifications Nos. 5,246,798 and
4,086,392 respectively.
It has been surprisingly found that the low water loss battery of the present
invention having the aforementioned combination of the "treated separator"
and the particular "additive", such as herein described, provides, due to a
synergistic effect, a substantial improvement in the suppression of the
evolution of gaseous hydrogen and the retention of water, as compared to a
similar battery not having the said "combination". A convenient method of
measuring water loss is to measure the quantity of gas emitted at the anode
due to the breakdown of water.
To evaluate the effectiveness of using the combination of the "treated
separator" and the "additive" in the lead-acid storage battery, according to the
invention, water-loss tests were carried out on the battery. The sample
(reference) battery used in the tests is a Normal Hybrid Battery. Hybrid battery
is constructed to comprise a positive electrode having a grid made of a lead-
antimony alloy containing anywhere from about 1 to 2.5 per cent by weight
antimony and more preferably 1.6 to 1.7 per cent by weight antimony and a
negative electrode having a grid made of a lead-based alloy comprising lead-
calcium/ lead-calcium-tin.
One such normal Hybrid battery was taken for reference purpose (referred to
herein as 'Battery X1'). Also, three more Hybrid Batteries were arranged with
the following combinations:
(A) Hybrid Battery having an "additive" only (hereinafter referred to as 'Battery
A');
(B) Hybrid Battery having "treated separator" (hereinafter referred to as
'Battery B') and
(C) Hybrid Battery having both "additive" and "treated separator" (hereinafter
referred to as 'Battery C').
To prepare the Hybrid Battery of (A) type, containing the zinc additive, the free
electrolyte from the Hybrid battery was removed by inverting and draining and
then adding a measured amount of the zinc additive of ZnSO4.7H20 to the
drained electrolyte and then refilling the battery with the modified electrolyte to .
the same level and charging to ensure thorough electrolyte mixing.
For conducting the comparative water-loss tests, the aforementioned batteries
(A, B, C and X1) were fully charged before an overcharge at a constant
voltage of 14.4 V. Each of the batteries (A, B and C) alongwith the reference
battery (X1) was floated at a temperature of 60o C for a period of first 21 days,
and subsequently, for a period of following second 21 days. The current was
recorded for each case. The current was found to increase slightly with time
due to poisoning of the negative plates by antimony. After carrying out the
tests, the results were evaluated. The average values of these evaluations
were then compared with each other. The comparative analysis of the float
current and water loss characteristics of the tree types of batteries, namely,
Battery A, Battery B and Battery C, in relation to the reference Battery X1, are
presented in Figures 2A, 2B, 2C, 3A, 3B, 3C and 4 of the accompanying
drawings.
As shown, when floated at the temperature of 60o C, at the end of the second
21 days, the equilibrium float current, as recorded, was found to be reduced
significantly for the Hybrid Battery C, which was provided with both "additive"
and "treated separator". Clearly, the Battery C, with the combination of the
particular "additive" and the "treated separator" yields substantially improved
efficacy due to the synergistic effect of the combination, that being
significantly better than the Hybrid Battery A having "additive" only or the
Hybrid Battery B, having the "treated separator" only. This is also evident from
Figure 4, which illustrates a schematic comparison of the water loss tests,
based on Battery X1 {reference Hybrid battery) vis-a-vis Battery A with
"additive" in electrolyte vis-a-vis Battery B with treated separator" vis-a-vis
Battery C (according to the invention) wfth combination of "treated separator"
and "additive" being provided in the electrolyte. From the comparative
analysis data, as presented, lead-acid performance is found to have been
improved substantially by the use of the combination of the "treated separator"
and the "additive", that being significantly better than what is achieved from
the reference Hybrid battery (Xi).
It is clear that provision of the said combination of the "treated separator" and
the "additive" in the low water loss battery, according to the invention, gives
the battery significantly lower water usage. The said combination has been
found to inhibit the evolution of gaseous hydrogen effectively and thereby
attenuating the loss of water significantly. Thus, important synergistic effects
are found in using the said combination in the lead-acid batteries.
The amount of the additive of ZnSO4.7H20 used in the battery of the
invention should be such that it is sufficient to decrease the float current
during constant voltage overcharge and result in lower water losses. The
reduction in water loss as a function of zinc sulphate added to the electrolyte,
is shown in figures 5A and 5b, where the battery is floated at a temperature of
60s C, and in Fig. 6, where the battery is floated at a temperature of 80s C.
While the amount of zinc sulphate required may vary depending upon the
manner in which it is added to the battery, it has been found suitable to use
the additive concentration in the range of from about 0.3 to about 2.0 gm/1 in
electrolyte. However, for optimization of the concentration of the "additive" and
for achieving the desired result of the invention, it is preferable to use the
amount of zinc sulphate in the range of 0.5 to 1.1 gm/l in electrolyte, and more
preferably 0.6 to 0.9 gm/l in electrolyte.
According to preferred embodiments of the invention, although it Is desirable
to add the additive of ZnSO4.7H20 into the battery electrolyte, it can also be .
applied on the electrode, or it can be added to the active material paste used
for the electrodes.
It is to be understood that, apart from using the combination of the "treated
separator" and the "additive", the low water loss battery according to the
invention, also encompasses ordinary lead sulphuric acid storage battery with
conventional electrodes and sulphuric acid as electrolyte. Preferably, the
battery is a starter battery for motor vehicles.
The low water loss battery according to the invention works successfully in
case of Lead Acid batteries used in cars. However, the battery according to
the invention, as described herein, is not limited to the battery for a vehicle,
but, it is general. Hence, the invention can be used in varying operating
conditions and for different types of batteries.
Accordingly, while the invention has been described using a hybrid battery for
reference, those skilled in the art will appreciate that the experiment can be
conducted with a lead calcium battery, or a lead antimony battery (e.g. with 1
to 2.5 % by weight of antimony in the grids of the positive and negative
electrodes), even though a less significant reduction in water loss may be
obtained. This can be better understood from Figure 7, which shows the
comparative analysis of the water loss test carried on the low water loss
battery according to the invention (Battery C), vis-a-vis lead calcium battery
with both "additive" and "treated separator" (Battery Y), when compared to the
reference Hybrid battery (Battery X1). All the batteries, namely, Battery C,
Battery Y and Battery X1 were floated at a temperature of 60o C and at a
constant voltage of 14.4 V for a period of first 21 days, and subsequently, for
a period of following second 21 days. Clearly, Hybrid battery having the
"additive" and the "treated separator" (Battery C) was found to exhibit a
greater reduction in water loss, compared to that of the lead-calcium battery
having the "additive" and the "treated separator" (Battery Y).
Figure 8 illustrates a comparative analysis of the water loss test carried on the
lead-calcium battery with both Additive and treated separator (Battery Y), as
compared to a reference calcium battery C Battery X2' ), and the corresponding
experimental result obtained thereby.
Several battery applications demand superior and better cycle-life
characteristics, particularly at medium and higher depth of discharge as well
as battery ability to withstand higher operating temperatures, that is high
temperature endurance. For heavy-duty applications, lead-calcium grid is not
preferred. The calcium presents difficulties in the manufacture of lead acid
batteries because of the attendant need for precise control of impurities and
the tendency of calcium to oxidize on contact with air. As a consequence, the
manufacture of lead acid batteries utilizing calcium is more difficult and more
costly than the manufacture of the aforementioned antimony lead batteries.
Addition of calcium also results in an increase in the corrosion rate of the
. positive grid and deformation by elongation of the grid, that is, generation of
"growth". The growth tends to impair the electrical connection between the
grid and the active material so as to give rise to serious defects such as a
decrease in the battery capacity and short-circuiting caused by the
deformation Df the plate. Lead-Antimony batteries give good cycle life.
The foregoing is to be considered as illustrative only of the principles of the
present invention. Depending on the battery under test, the value of
equilibrium float current and the water loss, as measured, will vary and can be
experimented with. Further, since numerous modifications and changes will
readily occur to those skilled in the art, it is not desired to limit the invention to
the exact embodiment shown and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within the true spirit
and scope of the invention in the appended claims, and their equivalents.
AMENDED CLAIMS
received by the International Bureau on 15 October 2009 (15.10.2009)
1. A lead-add storage battery, with improved reduction in the rate of water
loss, characterized in that a polyethylene separator, treated with one or more
water-solubles non-ionic surfactants) is used in the said battery to retard
antimony poisioning of the negative plate, in conjunction with zinc sulphate
ZnSO4.7H2O as additive.
2. The lead-acid storage battery as claimed in clam 1, wherein the separator
is treated to retard the antimony poisoning of the negative plate with water
soluble non-ionic surfactant (s) either on the surfaces of the separator or on
the side of the separator turned towards the negative electrode or on the side
of the separator turned towards the positive electrode or on both sides of the
separator.
3. The lead acid storage battery as claimed in claim 1 or 2, wherein said water
soluble non-ionic surfactant(s) is/are selected from the group consisting of
oleylaminooxethylate, stearylaminooxethylaie, tallow fatty aminoxethylate,
coconut oil aminooxethylaie, coconut oil acid diethanol amidoxethyiaie,
coconut oil acid monoethanol amidoxethylate, dodecanedioic-acid-N,N-
diethylamide, decyialcohol oxethylate, octylalcohol-oxethylate, coconut oil
alcohol oxethylate, tallow fatty alcohol oxethylate, stearyl alcohol oxethylate,
oleyl alcohol oxethylate, oleic acid amideoxethylate, tallow fatty acid
oxethylate and tall oil fatty acid oxethylate, oxoalcoholoxethylate with 8 to 20
carbon atoms in the alcohol residue, fatty acid glycerinesteroxethylate such as
polyoxethylene glycerine monolaurate, -stearate, oleate or palmitate, castor
oil oxethylate and fatty acid sorbitan ester oxethylate of the Tween type.
4. The lead add storage battery, according to claim 1 wherein the
concentration of the zinc sulphate used in the battery is in the range of 0.3 to
2.0 gm/l in electrolyte.
5. The lead acid storage battery, according to claim 4, wherein the
concentration of the zinc sulphate is in the range of 0.5 to 1.1 gm/l in
electrolyte, and more preferably 0.6 to 0.9 gm/l in electrolyte.
6. The lead acid storage battery, according to any one of claims 1 to 5,
wherein the additive is added to the electrolyte.
7. The lead add storage battery, according to any one of claims 1 to 5,
wherein the additive is added to the active material paste, used for the battery
electrodes.
8. The lead acid storage battery, according to any one of the preceding
claims, wherein the battery is a normal Hybrid battery with a positive electrode
having a grid made of a lead-antimony alloy containing 1 to 2.5 per cent by
weight antimony, and more preferably 1.6 to 1.7 per cent by weight antimony,
and a negative electrode having a grid made of a lead-based alloy comprising
lead-calcium/ lead-calcium-tin.
9. The lead acid storage battery, according to any one of the preceding
claims, wherein the battery is a lead-calcium battery or a lead-antimony
battery.

The invention discloses a low water loss battery, in particular lead-acid battery, with improved reduction in the rate
of water loss, wherein a treated separator against antimony poisoning and an additive in conjunction with the treated separator are
provided in the said battery. The separator is treated with chemical agents like water-soluble, non-ionic surfactants. The additive
can be zinc or a zinc compound, e.g. zinc sulfate.