Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Patent
1992-11-30
1994-07-12
Hickey, R. J.
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
320 32, H02J 710
Patent
active
053292189
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of regulating the charging of batteries containing a number of cells, for example NiCd cells, in which the battery is connected to a battery charger for impressing a current through the battery.
A plurality of different techniques for charging batteries containing, for example, NiCd cells are known in the art. Examples are constant current charging, constant voltage charging in which the charging current is based on the battery cell temperature and pressure, pressure and temperature charging, and pulse charging. The major advantage afforded by constant current charging is that the charger may be of extremely simple design, while its major drawbacks are those of being restricted to a temperature range of between 0.degree. and 40.degree. C. and of requiring an extremely long charging time at lower temperatures, since the permitted mean current under cold conditions is considerably lower than at room temperature. Furthermore, the charging itself takes place completely uncontrolled and without any adaptation whatever to the capacity of the cells to accept the charging energy. Constant voltage charging is also uncontrolled, but in this process the properties of the cell are utilized somewhat better. However, in this case also the charging time will be long, in particular at low temperatures. Because of the difficulties in providing pressure and temperature-sensing elements, pressure and temperature charging occurs only in extremely special and uncommon circumstances. In this case, the reason for this is that the practical obstacles are as good as insurmountable. In per se conventional pulse charging, the charging takes place in cycles of, for example, 1 Hz, the charging current being, for example, twice as great as the nominal discharging current. Pulse charging has proved to be more efficient than many other charging techniques, in particular at low temperatures. In conventional pulse charging, compensation is merely effected of poor control of the charging current of the battery. However, conventional pulse charging involves considerable charging time and relatively poor control over the different parameters.
SUMMARY OF THE INVENTION
The object of the basis of the present invention is to provide a novel method of regulating the charging of a battery containing a number of cells, for example NiCd cells, this method providing a complete charging of the battery in a considerably shorter time than has hitherto been possible both at room temperature and particularly at low temperatures.
The primary advantage of the method according to the present invention resides in the possibility of a complete charging of a battery in a considerably shorter time than has hitherto been possible, without any risk whatever of undesired pressure elevation in the individual cells arising from gas formation. While a charger for carrying out the method according to the present invention may appear to be relatively complex, its degree of complexity is undoubtedly the result of the extraordinary advantages afforded by the charger, which gives as good as 50% shorter charging times, and in many cases even shorter, than prior art chargers, this without any risk whatever of undesired gas formation in the cells. In addition, the method according to the present invention makes it possible to take into account the capacity of the individual cells to receive charging energy, whereby all cells in a battery will be given substantially the same charging level irrespective of whether any of the cells becomes fully charged before any of the others. In addition, the method according to the present invention has proved to permit charging of batteries at such low temperatures as -20.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the present invention will be described an greater detail hereinbelow, with particular reference to the accompanying drawing which shows a schematic cycle (not to scale) in diagram form for illustrating one embodiment of the method acco
REFERENCES:
patent: 3987353 (1976-10-01), Macharg
patent: 4396880 (1983-08-01), Windebank
patent: 4549127 (1985-10-01), Taylor et al.
patent: 4745349 (1988-05-01), Palanisamy et al.
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