Device for self-leveling of electrolyte in electric accumulators

A device for maintaining the electrolyte level in the accumulator of an electric battery includes a pneumatic chamber, with levelling members in it, connected to the accumulator, and a reservoir for supplying liquid to the pneumatic chamber. The levelling members assure a constant level of liquid in the pneumatic chamber. When the electrolyte level in the accumulator drops below a preset limit, the resulting reduction in pressure in the pneumatic chamber permits reservoir liquid to enter the accumulator, until the level of electrolyte in the accumulator rises enough to raise the pressure in the pneumatic chamber to stop flow of liquid into the accumulator.

This invention relates to a hydraulic device applicable for self-levelling 
or self-topping up of electrolyte of general batteries in electric 
accumulators. 
Referring to batteries of electric accumulators, particularly stationary or 
semi-stationary batteries, wherein remarkable time intervals may elapse 
between one and the next topping up or levelling of the electrolyte, the 
reduction in the electrolyte level may cause troubles and damages to the 
battery and also to the users therefrom supplied. These troubles would 
more occur in case of floating or buffer batteries of accumulators, and 
particularly in batteries associated with continuously operated electric 
generators, such as solar cells, wherein the relative plants are installed 
at locations that are unmanned or hardly accessible for rational and 
efficient maintenance. Further, in some types of accumulators, such as 
Pb-Ca batteries, as well in those of low percentage of antimony, while 
being the latter an acceptable solution for some use requirements, there 
however occurs upon water dissociation an undesireable increase in 
electrolyte concentration. 
It is the object of the present invention to obviate these and further 
drawbacks and automatically ensure the electrolyte levelling or topping up 
in the accumulator to provide, within determined limits, a constant 
electrolyte concentration throughout the accumulator operation. 
In is another object of the invention to provide a device for the above 
specified uses, which is of limited overall size, so that it can be 
applied to common stationary and semi-stationary accumulator batteries for 
traction and also to the transportable type of batteries. This is of 
substantial interest in case of batteries mounted on general vehicles, 
particularly railway cars, where the topping up operation is laborious 
also because of having to remove the accumulator from the vehicle. 
It is a further object of the invention to provide a device of the above 
specified type which, while still assuring the advantages set forth, can 
be also applied to accumulators of any type and at present marketed. 
A device according to the invention is characterized by having, in 
combination with the accumulator, a topping up liquid reservoir 
hydraulically and by gravity connected with a pneumatic chamber provided 
with levelling members assuring in said chamber a constant level of 
topping liquid and a predetermined pneumatic pressure, said levelling 
members being connected with the interior of the accumulator to detect the 
changes in level of the electrolyte, so that when the level of said 
electrolyte falls down below determined limits, a reduction in pressure 
occurs in said pneumatic chamber allowing the reservoir liquid to transfer 
into the accumulator until the electrolyte of the latter, on reaching the 
predetermined level, re-establishes in said pneumatic chamber the required 
pressure to cut off any further introduction of liquid into the 
accumulator. 
In practice, such a concept is liable to many embodiments, all of which are 
within the scope of the present invention. 
For example, the pneumatic chamber and conveniently also the topping up 
liquid reservoir may be integrally formed with the top portion of the 
accumulator housing, particularly where such a housing is made of molded 
plastic materials. Particularly in case of semi-stationary and also 
transportable accumulators, the device has a housing within which the 
pneumatic chamber and a vent chamber for the gases developed by the 
electrolyte are provided, at the bottom such a housing having a 
plug-shaped extension, through which a piezometric tube passes and 
immerges into the electrolyte, which extension removably and sealingly 
engages the vent gate of the accumulator battery. 
The invention will now be explained with reference to the appended drawings 
showing by way of example some embodiments of a device according to the 
invention.

The scheme related to of FIG. 1 shows at A the electic accumulator and at 
A1 its cover or lid, which as well known has a suitably shaped plug A2 for 
the vent of gases being developed by the accumulator electrolyte. For 
simplicity of representation, the accumulator plates have not been shown. 
According to the invention, a tube 10 is immersed for some length into the 
electrolyte of accumulator A, the tube forming as stated in the following 
a piezometric tube which is suitably secured to the accumulator cover or 
lid A1. At the top this piezometric tube 10 terminates with a section 12 
which through the bottom 14 of a housing 16 opens within the latter at an 
appropriate height or level, and this in connection with the explanation 
hereinafter given. This housing 16 is closed and forms a pneumatic 
chamber, in which a pneumatic pressure is built up and varies with the 
change of the liquid level provided time by time in said chamber. 
The liquid head within chamber 16 is provided by a conduit 18 connecting 
the bottom 14 of said chamber with the bottom of a reservoir 20 for the 
accumulator topping up liquid, such as distilled water. Reservoir 20 is 
positioned at a higher level than chamber 16 by a suitable height and is 
closed by a lid 22 fitted with a plug 24 having a vent hole for the 
passage of ambient air with said reservoir in connection with the 
functional characteristics of the device. 
The foregoing parts are arranged and positioned to one another at 
determined heights and such that suitable liquid levels are set therein. 
Particularly, and still referring to FIG. 1 of the drawings, reference 
letter H1 denotes the maximum level taken by the topping up liquid in 
reservoir 20, H2 the height as determined by the liquid in reservoir 20 at 
the top of the levelling conduit 12 and corresponding to the pressure 
within the pneumatic chamber 16. Reference letter H3 denotes the maximum 
height of the liquid head within chamber 16 as determined by the levelling 
conduit 12, whereby H1=H2+H3. Reference letter H4 denotes the level of the 
electrolyte of accumulator A between the liquid surface and the drawing 
end of the piezometric tube 10. Reference letter H5 denotes the pressure 
head achieved by the electrolyte within the piezometric tube 10 during the 
accumulator operation, and H6 denotes the back pressure exerted by the 
electrolyte in said pneumatic chamber 16, and H7 the change in level of 
the electrolyte according to which the device is operated. 
Head H1 is held constant either supplying in turn the reservoir(s) 20 with 
one or more cistern reservoirs or if said reservoir 20 is made as 
explained in the following with reference to FIG. 3. 
Referring to the foregoing, the device operating characteristics will now 
be envisaged. Initially and with pressure head H6=0, the full pressure of 
the liquid column H1 of reservoir 20 is effective within the piezometric 
conduit 10, thus lowering the level of the electrolyte therein. Thereby, 
the following three conditions would occur: 
H6&lt;H4; 
H6=H4; 
H6&gt;H4 
When H6&gt;H4 and accordingly H5=0, a determined volume of air bubbles out of 
the piezometric conduit 10 into the accumulator electrolyte exhausting in 
the air through the vent plug A2. A corresponding volume of topping up 
liquid passes by gravity from reservoir 20 into pneumatic chamber 16 and 
accumulator A. The passage of topping up liquid from reservoir 20 to 
accumulator A until the condition H6&lt;H4 is achieved. As soon as this 
condition is achieved, the passage of air from said pneumatic chamber 16 
and through accumulator A into the ambient is cut off, while at the top of 
said chamber a pneumatic pressure is built up corresponding to the 
specific gravity .gamma. and height of the liquid column H6, where the 
level of the electrolyte surface of the accumulator is increased by the 
section H7, whereby a balance is established between the pressures 
determined by the liquid columns H6 and H2. 
Let us now consider the levels occuring during the operation of accumulator 
A. Particularly, when H6&lt;H2, the pressure of the liquid column H2 prevails 
over the pneumatic pressure in the pneumatic chamber 16, whereby an 
overflow of the topping up liquid is caused from reservoir 20 through the 
piezometric conduit 10 into the accumulator. Topping up is stopped as soon 
as an equilibrium state is established between H6 and H2. 
On the other hand, when H6&gt;H2, the pressure of the liquid column .gamma.H6 
lowers the liquid level H3 in the pneumatic chamber 16, so that the liquid 
surface in said pneumatic chamber is below the top of the levelling tube 
12, thus cutting off the inflow of topping up liquid into the accumulator 
A. 
In practice, with H2 constant since H1 is constant, also H6 is nearly 
constant and accordingly the level of the liquid within the accumulator. 
The balance condition given by .gamma.H6=H2 will impose a value of H6 which 
is inversely proportional to the specific gravities .gamma. for the two 
liquids. It clearly appears that the maximum value for H2 and hence the 
height of reservoir 20 is only limited by the maximum immersion height H4 
taken by the piezometric tube 10 within the accumulator electrolyte. Thus, 
the optimum condition for ensuring a successful operation of the device is 
given by H2=.gamma.H6&lt;.gamma.H4. Therefore, the net volume of the 
pneumatic chamber 16, that is the liquid volume between the maximum level 
and minimum level (corresponding to height H3) should be lower than the 
inner volume of the immersed portion H4 of the piezometric tube 10 within 
the accumulator electrolyte. 
Considering now the variants of FIGS. 2 through 4, the parts like to those 
of FIG. 1 have been designated by like references. Particularly, in the 
case of FIG. 2, the piezometric tube 10a is intergral with the accumulator 
lid A1, also forming the bottom for the reservoir 20a of the topping up 
liquid. Within and at the bottom of said reservoir, the pneumatic chamber 
16a is provided and has disposed therein the levelling tube 12a forming 
the extension of the piezometric tube 10a which, in this case, is provided 
at least partially flexible for introduction into the accumulator A to the 
intended depth. Such a pneumatic chamber is in communication with the 
inside of reservoir 20a through a bottom hole 18a. The lid A1 is provided 
with a vent tube A2 which, by passing through said reservoir 20a, 
communicates with the atmosphere through a block of porous material 25 
retained by the plug 24a closing said reservoir 20a and also allowing the 
ambient air to enter therein for replacement of the liquid transfered to 
the accumulator A. 
Of course, where the accumulator battery has one or more elements or cells, 
the topping up for each cell is accomplished by a relevant device 
comprising the piezometric tube 10a and relative pneumatic chamber 16a, 
while the reservoir 20a may also be common for all of the battery elements 
or cells. 
In the variant according to FIGS. 3 and 4, the pneumatic chamber 16b is 
associated with a second chamber 26 forming an expansion or vent chamber 
communicating with the inside of accumulator A through a hole 28 drilled 
in the bottom wall 14b of said chamber and with the ambient through a hole 
30 at the top of said vent chamber 26. 
Laterally and below the levelling tube 12b, said pneumatic chamber 16b has 
an aperture 32 coupling such a chamber with a double connection 34-36 to 
retain pipings even of flexible type and serally interconnecting the 
chambers 16b of the devices of the involved elements or cells A with the 
topping up liquid reservoir 20b, not shown. 
The housing forming said chamber 16b and vent chamber 26 is shaped to 
terminate with a further cylindrical extension 38 provided with a stop rim 
40, thereby to form a plug which is removable and forcibly engageable with 
the gate B at the top of the housing relative to the involved element or 
cell of accumulator. A. Summarizing, the device shown in FIGS. 3 and 4 
forms the plug A2 closing the housing of the accumulator element or cell 
and of which the bottom wall 14b retains the piezometric tube 10b immersed 
in a predetermined section of the electrolyte of the involved battery 
element or cell. Obviously, said plug A2 may be otherwise shaped to be 
removably restrained to the vessel gate; for example, such a plug could be 
threaded for removable coupling with the relevant gate B. 
FIG. 5 is a schematic sectional view showing a further modified embodiment 
of the device applicable to stationary and traction batteries, as well as 
to other batteries where the available space is inadequate for introducing 
the piezometric tube or probe 10 into each of the elements or cells. 
The device shown is similar to that of FIGS. 3 and 4, except that the 
reservoir 20c is sealingly closed by a top wall 22c. On the other hand, 
the bottom 44 of reservoir 20c is provided with a gate 46 with closing 
plug 48, and such a bottom also has a tubular extension 50 located at a 
suitable position and of convenient length for the purposes which will now 
be set forth. 
The reservoir 20c is retained by the shaped edge 52 of a cistern 54 forming 
the support for said reservoir 20c, so that the latter can be located at a 
higher position than the element(s) or cell(s) of battery A and may be 
also removed from said cistern to be filled up with topping up liquid, 
such as distilled water or the like. 
This reservoir 20c and cistern 54 may be integral to each other, and in 
this case said reservoir 20c can be filled either by overturning the 
assembly, or even by rotating it through only 90.degree. if gate 46 is 
presented by one of the peripheral walls 52 of said cistern. The bottom 56 
of cistern 54 is provided with a collar 58 ensuring the communication with 
atmosphere for such a cistern and freely accomodating therein the gate 46 
presented by reservoir 20c in order to build up a liquid head H1 in said 
cistern which is constant and defined at the top by the edge of said 
tubular extension 50. The peripheral portion of cistern 54 has one or more 
connections 60 disposed below the surface of the liquid head of said 
cistern. 
Through a rigid and/or flexible piping 25c, the connection 60 hydraulically 
connects said cistern 54 with the element(s) or cell(s) A comprising the 
involved battery. Preferably, each of said elements or cells A retain on 
its lid a body A3 which, as above stated, may form the plug for the 
accumulator housing A. Such a body A3 is divided by a diaphragm 14c into 
two overlapping chambers, the upper chamber 16c of which is the pneumatic 
chamber of the device, while the lower chamber 62 is at the bottom 
provided with an aperture 63 immersed for some section in the electrolyte 
of the involved element or cell A. 
At one side the upper chamber 16c of body A3 is connected by connections 64 
and 60 with the interior of cistern 54, and at the other side by a second 
connection 66 and relative piping 25c with the upper chamber 16c of the 
body A3 associated with the element or cell A next to that involved. 
The two chambers 16c and 62 of body A3 are interconnected by two parallel 
coaxial tubular elements 10c and 12c, which are integral to the wall or 
diaphragm 14c, so as to form two vertical conduits for free passage 
between the two chambers of both the topping up liquid and air present 
within the device. 
The bottom portion of piezometric tube 16c is for some section immersed in 
the electrolyte of element or cell A to provide head H4. 
H5 denotes the height or level attained by the electrolyte within said tube 
10c during the device operation. 
H6 denotes the back pressure exerted by the electrolyte within the 
pneumatic chamber 16c, and H7 the change in level of the electrolyte, 
incident to which the device is operated. 
By the difference in height H2 between the free surface of the supply 
cistern 54 and the upper edge of tubular section 12c, the pressure exerted 
in chambers 16c and 62 is indicated. 
Similarly as above described, the balance condition is achieved when 
H2=.gamma.H6. 
As above stated, body A3 may be shaped also to form a plug removably 
applicable to the gate of element or cell A; moreover, such a plug should 
obviously assure the above mentioned liquid level conditions, and 
particularly provide the hydraulic heads H2 and H6. 
As a result, the functional behaviour of the device shown in FIG. 5 is 
similar to that previously considered. Particularly, when the reservoir 
20c (filled with the topping up liquid and placed in said cistern 54) is 
at the position shown in FIG. 5, a portion of the liquid stored in such a 
reservoir is outletted by gravity and collected in the underlying cistern 
54. As soon as level H1 is attained, at which the liquid surface in 
cistern 54 is coincident with the edge of tubular extension 50, the 
delivery of liquid is stopped. Due to the hydraulic connection between 
said cistern 54 and bodies A3 of the several battery elements or cells A 
as the liquid is transferred into the cistern, also all of the upper 
chambers 16c of said bodies are filled up, and this until the edges of the 
top tubular sections 12c are passed by some length, then to overflow into 
the underlying elements or cells A and establish in the latter the levels 
A4. As soon as this level is attained in any of elements or cells A, a 
pneumatic pressure is built up in the top portion of chamber 16c of the 
relevant body A3, which acts upon the liquid surface in said chamber, thus 
stopping the liquid transfer by gravity into the underlying element or 
cell A. When level H4 is attained in all of elements or cells A, the 
liquid in cistern 54 increases in level and engages the edge of the 
tubular extension 50, thus definitively cutting off the passage of liquid 
into such a cistern. Obviously, when the electrolyte level in any of 
elements or cells A drops to below its predetermined level, so that 
pressure H2 is no longer balanced, the pneumatic balance in chamber 16c 
will be upset, which causes an increase in the liquid level in such a 
chamber that, by overflowing into the underlying element or cell A, will 
thereby automatically re-establish the electrolyte level, and as soon as 
the balance conditions H2=.gamma.H6 occur, the liquid outflow is stopped. 
The liquid head H2 in cistern 54 remains unaltered until complete emptying 
of reservoir 20c. 
In order to avoid the drawbacks due to thermal variations, and particularly 
volume variations caused by heating of air in chambers 16c and 62 of body 
A3 of FIG. 5 (possibly also in the case of the device shown in FIGS. 1 to 
4) capable of causing an undue variation in the electrolyte level H4 in 
the accumulator, the device according to the invention is integrated with 
a compensation member A4. Such a member is shown in FIG. 6 and comprises a 
cap 68 placed on the bottom of chamber 62d, thereby to cover an overflow 
conduit 70 establishing the communicating between chamber 62d and interior 
of element or cell A, that is with the accumulator electrolyte since the 
edge of said cap is provided with slits 72. 
During the accumulator operation, particularly as the accumulator is being 
charged, should an increase occur in the air temperature in chambers 16d 
and 62d, this would cause an increase in pressure in such chambers, with 
resulting simultaneous lowering of the liquid levels H8 and H9 in said 
chambers and increase in the level of liquid within said cap 68. The 
increase in this latter level causes an overflow of liquid into vessel A 
through said overflow tube 70. Accordingly, while transferring liquid from 
the inside of cap 68 into the vessel A, the level H8 remains constant. 
The maximum expansion for the air in said pneumatic chambers 16d and 62d 
corresponds to the sum of the liquid volumes in said cap 68 and chamber 
62d, and height or level H10. 
In case of reduction in air volume in pneumatic chambers 16d and 62d, this 
would cause first an increase in levels H9 and H10 and then in level H8 
for the liquid in chamber 62d, thus inhibiting a not required topping up 
of liquid in accumulator A. 
In connection with the requirements as the case may be, the compensation 
member A4 may be modified and varied. For example, it could also comprise 
a resiliently deformable plenum chamber disposed between chamber 62d and 
the inside of accumulator A. 
The possibility is thus confirmed that the functionality of accumulator 
batteries can be maintained efficient and for an extended period of time, 
particularly where requiring a frequent liquid topping up in unattended 
installations. 
Modifications and changes can be made to the described and shown device in 
order to meet requested use requirements. For example, in the case of FIG. 
3, the reservoir 20 may be located at a suitable higher position than the 
level taken by the electrolyte in the several battery elements or cells. 
Such a reservoir, as well as that of FIG. 2, may be associated with the 
constant level supply device 50, 56 shown in FIG. 5. Additionally, the 
inventive device could be made so as to be an integrated part of the 
housing accomodating the involved battery element or cell. Finally, the 
device according to the invention may find other applications in addition 
to those herein specifically considered. Therefore, under this aspect the 
present invention is to be understood as extended to an accumulator which 
incorporates or is provided with the self-levelling device according to 
the present invention, still remaining within the scope of the invention 
and accordingly within the covering field of the invention patent.