Chemistry: electrical current producing apparatus – product – and – With heat exchange feature
Patent
1993-02-05
1995-01-17
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
With heat exchange feature
429183, H01M 1050
Patent
active
053824806
DESCRIPTION:
BRIEF SUMMARY
This invention relates to battery terminals, and in particular to a rigid connection between the battery cells leading out from the casing and heat dissipating means attached to the outside of the battery casing.
Many forms of battery are known, from a single cell, to arrangements comprising a plurality of interconnected cells as necessary to give a required energy storage capacity.
Batteries can also be divided into two main types; primary batteries which have a relatively short life and which are discarded when exhausted, such batteries often being a single cell and used for torches, radios and toys; and secondary batteries which are rechargable when exhausted and thus have a relatively long life, such batteries being used for starting automobiles, powering fork lift trucks and electric vehicles, and providing standby power for buildings and telephone exchange equipment.
Both primary and secondary batteries of dry alkaline type are known, as are secondary batteries of lead acid type.
Recently secondary batteries of sodium sulphur type have become known, such batteries having the advantages of light weight, high storage capacity and relatively quick recharging time. Further, such batteries use sodium and sulphur both of which are cheap and abundant materials.
Unlike conventional lead acid batteries in which a liquid electrolyte - dilute sulphuric acid separates two solid electrodes, in a sodium sulphur battery a solid electrolyte - beta alumina -separates two liquid electrodes, namely liquid sulphur and sodium electrodes.
Such a sodium sulphur cell is shown in FIG. 1 of the drawings, which is a perspective view of the cell with part broken away.
As shown the cell comprises a pressed steel case 1 in the form of a right circular cylinder containing a solid electrolyte cup 2 of beta alumina, the cup 2 containing a sodium electrode 3, while a space between the case 1 and the cup 2 contains a sulphur electrode 4. For use, the cell is maintained at a temperature of about 350.degree. C. such that the sodium and sulphur electrodes 3 and 4 are in liquid form.
The open end of the cup 2 is closed by an insulating disc 5 of alpha alumina, while the case 1 is closed by an annular steel disc 6.
The case 1 serves as a terminal for the sulphur electrode 4, while the sodium electrode 3 contains an elongate metal current collector 8 which extends axially of the case 1 out through the disc 5 where it is connected to a centre terminal disc 7 mounted on the disc 5, the necessary connections being made by welding.
The atomic structure of beta alumina is such that it acts as a selective ion filter. When the cell is discharging sodium ions pass from the sodium electrode 3 through the electrolyte 2 to react with the sulphur electrode 4 to form sodium sulphide. The chemical energy of this reaction is converted directly to electrical energy.
When the cell is charged, sodium and sulphur are regenerated from the sodium sulphide, the input electrical energy being converted into chemical energy.
To provide a battery capable of powering a vehicle it may be necessary for about 3000 cells as described above to be assembled together in arrays of series-connected arrangements of cells, the arrangements in each array being connected in parallel, and the arrays of arrangements being connected in series.
The cells forming the battery are enclosed in a heat insulating box which keeps the cells hot when no power is being drawn therefrom. Problems arise with the power leads which provide means for establishing connections to the terminals of the battery.
Batteries as under consideration are capable of giving high power output, and thus the leads connected thereto must be of a substantial diameter, say 6 mm. Due to the necessary size of such leads, i.e. their cross section, for them to serve their electrical function, they also provide good paths for heat to be conducted out of the battery. Such thermal conduction along the external cables can cause severe damage to the electrical insulation from the cable and associated dangers.
According to one
REFERENCES:
patent: 3758337 (1973-09-01), Fally et al.
patent: 4443524 (1984-04-01), Meinhold et al.
patent: 4585712 (1986-04-01), Wedlake
patent: 4600665 (1986-07-01), Sanders
patent: 5034290 (1991-07-01), Sands et al.
Kalafut Stephen
Silent Power GmbH fur Energiespeichertechnik
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