Rechargeable battery

A rechargeable battery is provided having positive and negative plates formed of flexible substantially solid sheets. The plates are each pasted with an active material and separated by a light weight absorbent separator. A light weight casing provides structural support for the plates and encases the battery's components. The battery is preferably a recombinant lead acid battery with its plates being formed of lead foil sheets. The casing is preferably reinforced to maintain a constant spacing between the plates by a plurality of support pins extending between upper and lower casing members through the plate sheets. Plates may be stacked one above another to provide a plurality of cells. In separate aspects of the invention, a battery may be formed having a polar plate that has positive and negative surfaces on its opposite sides. In another separate aspect of the invention a novel terminal arrangement is provided.

Portions of the subject matter of this application were discussed in United 
States Disclosure Document 222543 date-stampeded Mar. 20, 1989 in the U.S. 
Patent Office, which is incorporated herein by reference. 
The present invention relates generally to rechargeable batteries. More 
particularly, an improved approach to the design of batteries and 
especially sealed lead acid batteries is described. 
BACKGROUND OF THE INVENTION 
With the increasing popularity of portable electronic appliances, there 
have been extensive efforts to reduce the size and weight of their various 
components. In many circumstances, one of the principle limitations to 
such size reductions is the energy storage device. Accordingly, there have 
been ongoing efforts to develop energy storage devices that are lighter in 
weight, smaller in size and capable of storing the maximum electrical 
charge per unit weight and/or size. In order to remain economical during 
extended uses, it is important that the batteries be rechargeable. 
In recent years there have been substantial improvements in rechargeable 
battery technology; however, existing battery designs remain quite heavy 
in comparison with other electrical components. There are numerous 
batteries on the market, with the different designs using a wide variety 
of chemistries. The two most popular types of batteries that are used to 
power portable electronic devices are nickel cadmium (NICAD) batteries and 
sealed lead acid batteries. 
The most common and probably the best known battery construction is lead 
acid. Substantially all the existing automotive battery designs are lead 
acid based. One advantage of lead acid batteries is that they have very 
repeatable power delivery characteristics and may be recharged and 
overcharged repeatedly with minimal damage to the cells. Additionally, the 
power curve is consistent enough that the charge remaining in a cell at 
any given time can be relatively accurately predicted by merely measuring 
the cell's potential. Thus, a user can be easily warned well in advance of 
a loss of power. The major drawback of lead acid batteries is that they 
tend to be heavy; traditionally, large lead grids are used to form the 
battery's plates and the cells are flooded with an acid based electrolyte. 
Typically, the grids are structurally self supporting which increases 
their weight. Additionally, in order to ensure a reliable electrolytic 
seal between adjacent cells, in practice it is generally necessary to fomm 
a gas tight seal about each cell. 
A significant improvement to the traditional lead acid battery design is 
the recombinant battery. The recombinant lead acid battery differs from 
its predecessors in that substantially all of the electrolyte is absorbed 
within the separator between adjacent plates and/or an active paste 
applied directly to the plates. Gases evolved during operation or charging 
are not normally vented into the atmosphere, but rather are induced to 
recombine within the battery. With such an arrangement, no free acid is 
available, which allows the battery to be sealed and maintenance free. The 
elimination of free acid also provides a safer battery design. 
Several refinements have been made to recombinant lead acid batteries. For 
example, U.S. Pat. No. 3,862,861 describes a significantly improved lead 
acid battery design, which uses flexible, non-self-supporting grids within 
a recombinant lead acid battery design. Specifically, the flexible grids 
are fabricated from a very high purity lead and are separated only by a 
microporous fiberglass material that retains the electrolyte within the 
separator itself. Such an arrangement improves the energy storage per unit 
weight characteristics of lead acid batteries since the separator 
structure is significantly lightened. 
U.S. Pat. Nos. 4,383,011, 4,525,438 and 4,659,636 all describe alternative 
recombinant lead acid battery designs. The '636 design stacks a plurality 
of flattened cells in order to produce a somewhat flattened battery unit. 
Unfortunately, even these relatively improved lead acid battery designs 
only match the energy density (watt-hours of energy stored per unit weight 
of battery) and the packaging density (watt-hours of energy stored per 
unit volume of battery) of NICAD cells. 
An important technical requirement of lead acid batteries is that the 
spacing between plates must be maintained at a constant distance. As is 
well known in the art, if the plates of a lead acid battery are not 
sufficiently constrained, the plates will expand and the battery degrades 
relatively quickly. Accordingly, the casing must be sufficiently strong to 
prevent separation of the plates under the influence of the considerable 
forces that can act on the plates during a charge/discharge cycle. 
Two areas of prior art recombinant batteries are particularly bulky and/or 
heavy. The first is the electrodes which are typically fabricated from 
lead grids and the second is the casing structure which is typically 
heavily reinforced. Prior art batteries, such as those described above, 
merely increase the thickness of the casing in order to prevent 
deformation of their casings and/or electrodes. However, such external 
support is disadvantageous since it is quite bulky. Therefore, there is a 
need for an improved light weight battery plate support structure. 
Although nickel-cadmium batteries tend to have slightly better energy and 
packaging density characteristics than conventional lead acid batteries, 
they also have numerous drawbacks for powering portable electronic units. 
Among the most noticeable is that their power delivery curves vary a great 
deal depending upon their charging and recharging history. Thus, they are 
unsuitable for use in devices that must be recharged at varying intervals. 
Accordingly, there is a need for an improved battery design that has 
improved energy density and packaging density characteristics. 
SUMMARY OF THE INVENTION 
It is a primary objective of the present invention to provide an improved 
rechargeable battery construction that has relatively high energy and 
packaging densities. 
Another object of the invention is to provide an internal casing 
reinforcement structure that is both strong and light in weight. 
To achieve the foregoing and other objects and in accordance with the 
purpose of this invention, a rechargeable battery is provided having 
positive and negative plates formed of flexible substantially solid 
sheets. The plates are each pasted with an active material and separated 
by a light weight absorbent separator structure. A lightweight casing 
provides structural support for the plates and cooperates to encase the 
plates, active material and separator. The battery is preferably a 
recombinant lead acid battery with its plates being formed of lead foil 
sheets. 
The casing is preferably reinforced to maintain a constant spacing between 
the plates by a plurality of support pins extending between upper and 
lower casing members through the plates. In a preferred embodiment, the 
pins are formed from complementary pin portions that extend inward from 
the opposing upper and lower casing members respectively. The pin portions 
may be formed integrally with the upper and lower casing members. 
In an alternative embodiment of the battery, a plurality of stacked cells 
are formed bY stacking pasted planer plates one above another with 
separators in between the adjacent plates. 
In an alternative aspect of the invention, a rechargeable polar lead acid 
battery is formed wherein a polar plate is positioned between the positive 
and negative plates. The polar plate is formed from a sheet of lead foil 
and has positive and negative surfaces. The resultant battery has multiple 
cells that are combined in series to form a higher potential battery. 
In another separate aspect of the invention a novel terminal arrangement is 
provided that extends outward from one end of the battery casing. The 
terminal arrangement includes a pair of spring loaded vertically aligned 
contacts facing upward and downward respectively. The upward facing 
contact is adjacent the outer surface of the upper casing and the downward 
facing contact is adjacent the outer surface of the lower casing. The 
vertically aligned contacts are coupled to the battery's positive and 
negative plates respectively. A pair of horizontally aligned contacts are 
also provided which face towards opposite sides of the casing such that 
the horizontally aligned contact pair face substantially perpendicular to 
the vertically aligned contact pair.

DETAILED DESCRIPTION OF THE DRAWINGS 
As illustrated in the drawings, the embodiment of the invention chosen for 
the purposes of illustration is a flat recombinant lead acid battery 20. 
Externally, as seen in FIG. 1, the battery has matching upper and lower 
casing members 22, 24 and a terminal arrangement 30. Referring next to 
FIGS. 3 and 4, the internal structure includes spaced apart positive and 
negative plates 42, 44 which are pasted with active materials 45 and 47 
respectively. A separator 49 electrically isolates the plates. A 
multiplicity of pins 50 extend through the plates and separator to support 
the casing in order to maintain a constant spacing between the plates 
during operation and recharging. The pins 50 are formed from complementary 
pin portions 52 and 54 which are integrally formed with the upper and 
lower casing members 22, 24 respectively. 
As discussed above, it is important to reinforce the casing to maintain a 
constant spacing between the plates. Since it is contemplated that the 
casing will be fabricated from a light weight and relatively inexpensive 
plastic material, the pins 50 are provided in order to provide internal 
structural support to the casing. It should be apparent that internal pins 
are a much lighter mechanism for supporting casing walls then merely 
thickening the walls to obtain the desired strength as has been 
extensively practiced in prior art battery designs. As seen in FIG. 2, the 
upper casing 22 has a matrix of male pin portions or posts 52 that extend 
inward from its interior surface. The lower casing 24 is similarly formed 
except that it has female pin portions or posts 54 designed to receive the 
upper casing post 52. The posts 52 and 54 are arranged such that they mate 
when the battery is assembled. Once the battery is fully assembled as 
described below, the posts are joined together. In the described 
embodiment, the casing members 22 and 24 are formed from plastic and the 
posts are ultrasonically welded together to form continuous pins. At the 
same time the upper and lower casing members are ultrasonicly welded 
together to seal the battery. The actual spacing of the pins 50 will vary 
a great deal depending upon the requirements of a particular battery. By 
way of example, one half inch centers have proven to be an effective 
spacing for typical planer battery designs. 
The positive and negative plates 42 and 44 are formed from sheets of lead 
foil. The lead foil is not a structural member and can therefore be of a 
high purity and extremely thin. Since the foil is very thin, it is formed 
as a substantially continuous sheet of foil as opposed to a grid structure 
which is common in prior art lead acid battery plates. Although thinner 
sheets are generally preferable to thicker sheet, (since they are lighter 
in weight), in practice sheets of any thickness could be used. By way of 
example, suitable foil thicknesses of less than 0.01 inches may be used. 
The plates 42 and 44 are each pasted with a suitable active material that 
includes a large amount of lead based compounds and/or free lead. Paste 
mixtures typical to conventional recombinant lead acid batteries may be 
used. A porous separator material that is capable of absorbing and 
retaining large amounts of free electrolyte is used as separator 49. A 
suitable separator material is a conventional high porosity microporous 
fiberglass. Commercially available microporous fiberglass having interior 
openings occupying over 90% of the materials volume work well. One of the 
important functions of the separator is to maintain a constant spacing 
between the batteries plates. The separator 49 is somewhat resilient. When 
the battery is assembled with the pasted plates, the separator is 
compressed somewhat. Therefore, it exerts a continuous force pushing 
against the plates to maintain the desired minimum plate spacing. 
When assembling the described battery, a suitable matrix of holes 55 is 
punched into each plate 42, 44 in order to fit over the posts 52 and 54 
respectively. Otherwise the foil forms a substantially continuous sheet as 
opposed to a conventional grid structure. It should be appreciated that 
the foil nature of the plates makes it extremely easy to punch the desired 
matrix of holes. 
It is generally desireable to supply the battery with as much electrolyte 
as possible without flooding the battery. That is all of the electrolyte 
added should be retained within the separator 49 and the active materials 
45, 47. Thus, when the battery is filled with electrolyte, care must be 
taken to insure that the correct amount of electrolyte is added. Although 
recombinant lead acid technology is used to fabricate the battery, at 
times overcharging or malfunctions of the battery may lead to the 
generation of significant amounts of free gases within the internal cavity 
of the battery. Accordingly, a conventional pressure relief device 57 is 
provided to release the gases in the event of a significant 
overpressurization. In the embodiment shown in FIG. 3, the pressure relief 
device is a conventional bunson valve having a rubber cap 58 journaled 
over one end of a plastic pipe 59. The opposite end of plastic pipe 59 
opens into the interior of the battery casing. 
The terminal arrangement 30 extends from the front end of the casing. As 
described in more detail below, the terminal arrangement has a pair of 
vertically aligned contacts 64, 74 and a pair of horizontally aligned 
contacts 65, 75 which are both arranged to electrically couple the battery 
to electronic devices. 
The described planar battery construction is particularly well suited to 
both internal and external stacking in order to provide a battery or 
battery pack having any desired voltage potential and/or capacity. 
Reference is next made to FIG. 5, which shows a three plate configuration 
having two negative plates in order to approximately double the battery's 
capacity when compared to the two plate configuration described above. In 
this embodiment, two pasted negative plates are secured to the upper and 
lower casing members 22 and 24 respectively. A pair of porous separators 
49 are positioned adjacent the inner surfaces of the negative paste 
materials. A substantially continuous sheet of lead foil which is pasted 
on both sides with a positive active material 45 is disposed between the 
separators 49 to form a single positive collection plate having two active 
surfaces. The resultant battery is a single lead acid cell having a 
potential of slightly over two volts. 
Referring next to FIG. 6, a multi-cell battery construction will be 
described. A six cell, 12 volt battery 120 is constructed having a 
positive plate 42 carried by upper casing member 122 and a negative plate 
44 carried by lower casing member 124. As in the previous described 
embodiments, the plates are pasted with a conventional active material. 
Additional cells are formed by inserting dual plate structures 140 between 
the spaced apart positive and negative plates 42 and 44 with separators 49 
being placed between adjacent dual plate structures 140 as well as between 
the outer dual plate structures and plates 42 and 44 respectively. 
The dual plate structures 140 are formed by placing a pair of lead foils 
142 and 144 back to back. One of the lead foils (foil 144) is pasted with 
a negative active material 47 while the other (foil 142) is pasted with a 
positive active material 45. The back to back foils are placed below the 
positive plate 42 with a separator 49 disposed between the positive plate 
42 and the negative foil 144. Thus, the positive foil 142 faces towards 
the negative plate 44. At this point two cells have been formed. 
Additional cells are fabricated merely by stacking additional dual plate 
structures 140 below the first and inserting separators 49 between the 
additional dual plate structures as seen in FIG. 6. In that figure, six 
cells are formed by placing five dual plate structures 140 between the 
spaced apart positive and negative plates 42 and 44. Of course, separators 
49 are positioned between adjacent dual plate structures in order to 
maintain the desired plate spacing. Similarly, separators 49 are 
positioned between the top dual plate structure and the positive plate 42, 
as well as between the bottom dual plate structure and the negative plate 
44. As in the previously described embodiments, internal support pins 50 
extend between the upper and lower casings in order to maintain the 
overall spacing between plates. Since the separators 49 act as spacers, 
the actual spacing between opposing foils remains constant as well. 
Since the positive and negative foils 142 and 144 within each dual plate 
structure are maintained at the same potential, it is not necessary to 
isolate the plate foils, so long as the electrolyte within each cell does 
not leak between the opposite foils. Indeed it is important to have good 
contact between the back to back plates. As described with respect to the 
first described embodiment, the plates are held compressvely in place by 
the combined spring forces of the separators and the casing pins. 
To prevent leakage of electrolyte between the adjacent cells, the plates 
may be cut such that they have slightly larger dimensions than the 
separator 49. Then isolation rings 157 having substantially the same 
thickness as the separators 49 may be inserted about the various 
separators such that they are sandwiched between the adjacent dual plate 
structures as well as between the outer dual plate structures and the 
positive and negative foils 142 and 144. The isolation rings 157 encircle 
the separators to maintain a good seal about the ends of the plate. 
In practice, if the proper amount of electrolyte is used initially, 
virtually all of the electrolyte will remain absorbed within either the 
active paste materials 45, 47 or the microporous separator 49 via surface 
tension. Thus, the back to back plate foils 142 and 144 may be pressed 
together as shown in FIG. 6. Since virtually all of the electrolyte 
remains within the active material paste and the separator, there is very 
little migration of electrolyte between the back to back positive and 
negative pastes. Accordingly, it is not necessary to tightly seal the 
holes 155 through which support pins 50 pass. 
Referring next to FIG. 7, a polar battery having a single continuous foil 
acting as a positive plate for a first cell and a negative plate for an 
adjacent cell will be described. The polar battery 220 closely resembles 
the multicell battery described above with respect to FIG. 6. However, the 
polar battery 220 uses a polar plate 240 formed of a single lead foil 
sheet in place of the two lead foil sheets provided within the dual plate 
structure 140. One side of the polar plate 240 is pasted with a positive 
active material 45, while the opposite side is pasted with a negative 
active material 47. The use of a polar plate eliminates the need to 
electrically couple serially connected cells. In all other manners the 
polar battery may be formed in exactly the same way as the multicell 
battery previously described. Thus, the six volt battery shown in FIG. 7 
has positive and negative pasted plates 42 and 44 which are placed against 
the upper and lower casing members 222 and 224 respectively. Two pasted 
polar plates 240 are stacked between the positive and negative plates with 
the negative sides of the polar plates facing the positive plate 42 and 
the positive sides of the polar plates facing the negative plate 44. The 
number of cells within the battery can be readily changed to provide any 
desired potential. 
Referring next to FIGS. 8 and 9, a preferred battery terminal arrangement 
will be described. The terminal arrangement 30 has four contact points. 
Two are positive contact points and two are negative contact points. A 
positive contact member 60 is coupled to the positive electrode 42 by 
positive lead 62. The contact member 60 has two contact points 64 and 65 
and is arranged to act as a spring with respect to both of the contact 
points. The contact member has a U-shaped portion 66 one leg of which is 
coupled to the positive lead 62. The other leg is extended to form the 
contact points 64 and 65. Contact point 64 is also U-shaped and extends 
substantially perpendicularly with respect to the U-shaped portion 66. 
Thus, the U-shaped portion 65 acts as a spring that urges contact point 64 
outward. The contact member then extends beyond U-shaped contact point 64 
in line with the second leg of the U-shaped portion 66. The contact point 
65 depends from the end of the extension in a manner that is substantially 
perpendicular to the extension so as to provide a spring biasing for the 
second contact point 65. 
The negative contact member 70 is formed in the same manner as the positive 
contact member and forms negative contact points 74 and 75 which are 
positioned opposite the positive contact points. Thus, contact points 64 
and 74 are vertically aligned, while contact points 65 and 75 are 
negatively aligned as can be seen in FIGS. 8 and 9. The negative contact 
member 70 is coupled to the negative electrode 44 via negative lead 72. 
The positive and negative leads 62 and 72 may be formed integrally with 
the plates 42 and 44 respectively so as to be mere extensions of the foil 
plates. Thus, during fabrication of the plates, the appropriate plate/lead 
structure may be punched from a lead foil sheet. 
The described contact arrangement is particularly well suited for stacking 
batteries to form battery packs having a plurality of serially connected 
batteries. Specifically, the vertically aligned contact points 64 and 74 
extend just slightly above the planer outer upper and lower surfaces of 
the battery. Since the contact points are spring loaded the contacts 
within the pack that are coupled to an adjacent battery contact are 
readily pressed inward such that they are substantially coplaner with the 
outer surface of the battery to form a good solid spring loaded connection 
between the serially stacked batteries. The horizontally aligned contacts, 
allow stacked batteries and/or battery packs to be recharged using a 
continuous bus having extended parallel contact surfaces. Like the 
vertically aligned contacts, the horizontally aligned contacts are spring 
loaded to provide solid electrical connections with the devices they are 
plugged into. 
A pair of protective ears 81 and 82 are positioned on opposite sides of the 
horizontally aligned contacts 65 and 75 to protect those contacts from 
damage. The ear 82 positioned adjacent the positive contact 65 is a bit 
thicker than ear 81. Thus, electrical receptacles can be designed to 
cooperate with the ears 81 and 82 to prevent inadvertently reversing the 
polarity of a battery or a battery pack by plugging it into an electronic 
device or recharger the wrong way. 
Although only a few embodiments of this invention have been described 
herein, it should be understood that the present invention may be embodied 
in many other specific forms without departing from the spirit or scope of 
the invention. Particularly, it should be appreciated that the internal 
support of the battery casing may be accomplished using many designs other 
than the described pin structure. The planer battery structure described 
is particularly well suited for stacking and has a high packaging density. 
However, it is contemplated that the advantages described herein may be 
applied to non-planer battery designs as well. Additionally, many of the 
advantages of the present invention are applicable to batteries that use 
chemistries other than lead acid. Therefore, the present examples and 
embodiments are to be considered as illustrative and not restrictive, and 
the invention is not to be limited to the details given herein, but may be 
modified within the scope of the appended claims.