High-energy battery with a temperature regulating medium

In a high-energy battery with a plurality of individual cells in a housing through which a coolant flows, it is suggested that the coolant be guided such that it thermally affects only one or both end faces of the cells.

FIELD OF THE INVENTION 
The present invention pertains to a high-energy battery for high operating 
temperatures (e.g. Na/NiCl.sub.2 or Na/S batteries operating at 
temperatures between 250.degree. C. and 400.degree. C.) with a plurality 
of cells arranged next to one another in a housing and with a liquid or 
gaseous medium flowing within the housing to influence the temperature of 
the individual cells. 
BACKGROUND OF THE INVENTION 
High-energy batteries, e.g., Na/NiCl.sub.2 or Na/S batteries, operate at 
temperatures between 250.degree. C. and 400.degree. C. These batteries are 
composed of individual tubular cells. The individual cells of one battery 
are to be maintained at the same temperature in order for the internal 
resistances of the cells to be the same. Different internal resistances 
would lead to different loads on the individual cells and consequently to 
different states of charge and discharge of the cells. Nonuniformities in 
the states of charge within the battery may lead to a reduction of the 
service life of the battery. 
During a discharge cycle of such batteries, the inner areas of the battery 
in particular are heated more strongly than the outer ones, because heat 
dissipates via the housing. During charging, the cells which are arranged 
closest to the electric heater in particular have a higher temperature 
than the cells that are located at a greater distance. 
The internal resistance leads to evolution of heat within the battery 
during discharge. This can be explained on the basis of the example of a 
27 kWh battery with a voltage of 150 V and a capacity of 180 Ah: During a 
2-hour discharge, i.e., discharge with a current of 90 A, it is necessary 
to continuously remove a waste power of ca. 2 kW. Part of the power loss 
can be accommodated by the thermal capacity of the battery, and the rest 
must be removed from the battery by means of a cooling system. 
For example, various possibilities of cooling such batteries are described 
in the documents German Offenlegungsschriften Nos. DE-OS 32,47,969, 
26,10,222, and 28,35,550. It is common to all these suggestions that the 
coolant sweeps past along the cells, and the heat is thus exchanged on the 
entire surface of the cell. These arrangements make little contribution to 
achieving temperature equalization between the individual cells of the 
battery. The temperature equalization, which takes place only very slowly, 
leads to nonuniform loads. Another disadvantage of these cooling devices 
is their complicated nature. For example, a special distribution system is 
installed in the battery according to the application in order to achieve 
uniform guidance of air along the cells. The distribution of air within 
the individual canals between the cells cannot be accurately calculated 
and must be optimized experimentally. If the conditions change within the 
battery (e.g., due to a change in the removal of heat via the walls of the 
battery), the air distribution must again be optimized in order to again 
ensure uniform temperature distribution. It is also necessary to redesign 
the geometry, e.g., of a distributor plate, each time the design is 
changed. 
SUMMARY AND OBJECTS OF THE INVENTION 
It is an object of the present invention is to provide a battery of the 
type described in the introduction, in which the heat due to energy losses 
is removed during the discharge of the battery and a uniform temperature 
distribution is guaranteed within the battery over all cells during 
charging, idling, and discharge, and which can be simply adapted to 
altered battery geometries. 
According to the invention, a high-energy battery such as a sodium based 
battery (e.g., Na/NiCl.sub.2 or Na/S batteries operating at temperatures 
between 250.degree. C. and 400.degree. C.) is provided including a 
plurality of cells arranged next to one another in a housing and with a 
liquid or gaseous medium flowing within the housing to influence the 
temperature of the individual cells. The housing is provided with means 
for guiding the medium within the housing such that one or both of the two 
ends of the cells are brought directly or indirectly into heat-exchanging 
contact with the medium for influencing the temperature. 
The invention provides the battery cells and the housing such that top and 
bottom ends are positioned such that one or both of the ends are exposed 
to the temperature regulating medium and such that the temperature 
regulating medium does not substantially influence the side walls of the 
cells, wherein the side walls of adjacent cells are positioned facing each 
other. 
It was surprisingly found in experiments that the heat due to energy losses 
does not need to be removed over the entire surface of the tubular cell, 
but it is fully sufficient for the coolant or the medium used for 
temperature equalization to flow through only one or both ends of the 
tubular cell. The task is accomplished according to the present invention 
by the medium for removing the heat or equalizing the temperature flowing 
only around the upper and/or lower end of the tubular individual cell. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which a 
preferred embodiment of the invention is illustrated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings in particular the invention embodied therein 
comprises a battery provided by individual sodium cells 1 (i.e., 
Na/NiCl.sub.2 or Na/S battery cells operating at temperatures between 
250.degree. C. and 400.degree. C.) which are positioned within a housing 2 
wherein the housing cooperates with guide means 50 for generating and 
guiding a temperature influencing flow. The battery shown in a simplified 
manner has only 8 individual cells 1, which stand upright and are arranged 
in two rows of four cells each arranged next to one another within the 
housing 2. The arrows shown indicate the directions of flow of the medium 
controlling the desired temperature. The housing is designed as a 
thermally insulating housing in the known manner. The cells 1 are 
preferably designed as cylindrical cells. 
In this high-energy battery with cylindrical cells which are packed 
densely, a power loss of ca. 2 kW is generated during a 2-hour discharge 
at a storage capacity of 27 kWh. This power loss is generated over the 
entire volume of the individual cell. The heat that is generated due to 
the power loss must be removed in order for the battery temperature not to 
rise uncontrollably. This can be achieved simply by placing the cells into 
a rectangular battery box and blowing the air over the cells from one end 
to the other in the longitudinal direction (FIG. 1) using a medium guide 
means in the form of a blower 20. In this arrangement, the cells are 
cooled more intensely at the air inlet than at the outlet. To remove the 2 
kW, an air flow rate of &lt;50 m.sup.3 /hour is required. It is assumed that 
the air temperature increases by ca. 150.degree. K from the inlet to the 
outlet. 
The temperature difference between the inlet side and the outlet side can 
be reduced by causing the air to flow through the battery in the 
transverse direction rather than in the longitudinal direction (FIG. 2). 
An even more uniform temperature distribution can be achieved by causing 
the air to enter in the lower part of the battery on one side and to leave 
it in the upper part on the same side, or vice versa. The air is now 
guided over the cell packet in such a form that the air is sent under the 
cells to the end of the battery, then in the upward direction on the rear 
side, and to the inlet side over the cell packet (FIG. 3), or vice versa. 
The jacket surfaces of the cells 2 are preferably insulated against 
thermal contact with the ascending and descending medium in order to 
ensure that these rear cells are also thermally affected by the medium 
only at their ends. On the inlet side, the cells are cooled more intensely 
on the underside, because the temperatures of the air and the coolant are 
the lowest here. These cells are cooled less intensely on the top side, 
because the air already has a higher temperature here. Extensively uniform 
heat removal over all cells is achieved by this air guidance. 
In the case of the types of air guidance shown in FIGS. 1 through 3, 
extensively uniform flow is achieved under and above the cells. The design 
of a battery with this air guidance is relatively simple, because space 
for air guidance need be provided only beneath of the cell packet and in 
the rear part of the battery, preferably over the entire width of the 
battery. Due to the design, a space is available above the cells, so that 
the medium is able to sweep over the cells. The principle of this cooling 
can also be adapted to various battery geometries as desired, i.e., a 
coolant can thus be admitted even into quadratic batteries or very long 
batteries in a simple manner. 
A comparable type of guidance of the coolant can also be used for 
temperature equalization within the battery. As was mentioned above, it is 
important for all cells of one battery to be at the same temperature 
level. This is achieved according to the present invention not by 
exchanging the medium, as is done in the case of cooling, but by 
circulating the medium in a closed cycle within the battery. Based on the 
example of a rectangular battery housing, e.g., the following procedure is 
followed (FIG. 4): Using a blower 3, which is installed in the battery 
housing 2, the medium is caused to flow past under the cells, in the 
upward direction on the rear side, past the cells, and back to the blower 
on the front side, or vice versa. Thus, a closed cycle is obtained for the 
medium, which provides for temperature equalization within the battery. 
As was described above, this arrangement applies to cells arranged 
vertically in the housing. If the cells are arranged horizontally, the 
medium is guided on the side, so that the ends of the cells come into 
contact with the medium in this case as well, and are thus able to bring 
about cooling or temperature equalization. According to another 
embodiment, an arrangement according to FIGS. 5 and 6 has also proved to 
be useful. An empty tube 4 is arranged in the middle of the upright cell 
packet. A blower 3 is installed in said empty tube 4 or in its vicinity. 
Said blower 3--e.g., an impeller in this case--blows the medium through 
the empty tube, after which it is guided radially to the outside under the 
cell packet, upward on the sides, and back to said empty tube 4 with said 
blower 3 above the cells. Said blower may also be arranged such that it 
draws the medium through said empty tube, thus reversing the direction of 
circulation of the medium. This arrangement of the medium guidance has 
proved to be particularly advantageous in batteries with a more or less 
quadratic base. 
High-energy batteries which operate at elevated temperatures must be 
reheated during the idling and charging periods in order to compensate for 
the heat dissipation via the housing. If these batteries have low 
discharge rates, i.e., discharges taking more than ca. 2 hours in order to 
discharge the entire capacity of the battery, little or no cooling is 
needed, but only an auxiliary heater is required in order to compensate 
for the heat dissipation via the housing. In this case, the heater may be 
arranged in the ascending medium flow, and the blower may be eliminated if 
desired. The medium is now circulated solely by convection. 
In the case of more rectangular battery housings, which have no central 
empty tube, the heater is arranged either on a front side or on a side 
surface. This leads to the medium circulating around the cell packet. In 
the case of batteries which are provided with an empty tube which is 
located in the middle of the cell packet, the heater may be integrated 
within the empty tube, as a result of which the medium will rise in the 
empty tube and also circulate around the cell packet. 
The devices provided to pass the medium for cooling or temperature 
equalization above or beneath the cells have also proved to be useful when 
two cell packets are arranged one on top of another, i.e., vertically 
standing cells in two planes. It is sufficient in this case to pass 
through the medium horizontally between the two packets in order to 
adequately cool the entire battery or to provide for adequate temperature 
equalization. 
It should also be mentioned that the system described for cooling or 
temperature equalization in batteries is also suitable when cells with 
rectangular or other cross-sectional shapes rather than tubular 
cylindrical cells are used. The height of the cells also exerts a 
substantial effect. In the simplest case, air can be used as the medium. 
However, it is also possible to use liquid media, which are preferably 
located in a corresponding tube system. 
The cells or the cell packets are now arranged standing on a cooling plate 
through which the medium flows, and another cooling plate, through which 
medium flows, may also additionally be arranged horizontally on the cell 
packet. To remove the heat, a heat exchanger is to be provided outside the 
battery, along with a pump, in order to transport the liquid medium 
through this tube/plate system. In the case of heat equalization brought 
about without a pump, the heater is arranged in the ascending part of the 
liquid system, i.e., on a front surface or on a side surface or in the 
central empty tube of the battery. 
The ends of the cells are meant as the upper and lower end faces or front 
surface areas of the cells. The medium may be formed by gaseous and liquid 
substances. Gaseous substances, e.g., air, are generally preferable. 
While a specific embodiment of the invention has been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.