Electricity: battery or capacitor charging or discharging – One cell or battery charges another
Reexamination Certificate
1999-07-12
2001-01-30
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
One cell or battery charges another
Reexamination Certificate
active
06181100
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a battery charge/discharge power supply apparatus for charging and/or discharging storage batteries, and more specifically, to a battery charge/discharge power supply apparatus which can reuse the electric power discharged from a storage battery for recharging the same or a different battery.
BACKGROUND OF THE INVENTION
In recent years, owing to the rapid increase in portable devices and the development of electric automobiles, the demand for storage (secondary) batteries is greatly increasing. Storage batteries are produced by assembling the electrode made of active materials in a discharged condition. Before shipping the storage batteries in the market, the batteries must be charged with electricity or activated by repeatedly charging and discharging the same. It is also necessary to test samples of storage batteries to determine whether the batteries satisfy the intended performances such as cycle life by repeating charge/discharge operations.
This invention is directed to a power supply apparatus to be used for such purposes by charging and/or discharging storage (secondary) batteries. In the conventional technology, when charging a battery, a DC (direct current) power source converted from an AC (alternating current) source, i.e., the commercial power source is used. When discharging the battery, a discharge load is used, which is typically a resistor or an electric load. In the conventional technology noted above, the electric energy stored in the storage battery is consumed by the discharge load. As a result, a large amount of electric energy is wasted. For this reason, the conventional method is disadvantageous.
Under the circumstances, as disclosed in Japanese Laid Open Patent Publication Nos. 2-261020 and 7-222369, there has been an attempt to effectively use the energy discharged from a storage battery. In the above patent publications, it is disclosed that the energy discharged from the storage battery is recycled by feed-backing the discharged energy to an AC power source so that the AC power is converted again to a DC power to charge the storage battery.
However, since these methods convert the DC power discharged by the storage battery into the AC power by using an inverter, it is difficult to obtain an AC power with normal sine waves. In other words, the AC power inverted from the DC power involves noise and distortion. In order to obtain an AC power source having normal sine waves, i.e., low distortion or noise in the wave form, a high quality control circuit must be used, resulting in the increase of the overall cost of the apparatus.
In such a case, in order to achieve the energy saving or recycling with a simplified control circuit of relatively low cost, the recycled AC electric power tends to involve a significant amount of signal distortion or high voltage impulse (instantaneous) noise. Therefore, such a less expensive method may not be applied to noise sensitive electric apparatuses, such as computers or automatic machines which require high quality electric power. Such being the case, the method of using the recycled AC electric power is not appropriate.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to solve the above noted problems and to provide a battery charge/discharge power supply apparatus which can effectively recycle the electric energy discharged from a storage battery for achieving an energy saving.
It is another object of the present invention to provide a battery charge/discharge power supply apparatus which does not cause any noise or wave form distortion in the alternating current (AC) power source.
It is a further object of the present invention to provide a battery charge/discharge power supply apparatus which can accurately monitor and control the charge/discharge performance of a battery under test as well as an auxiliary battery in the apparatus.
In the battery charge/discharge power supply apparatus of the present invention, an auxiliary storage battery and a power converter are provided in the power supply apparatus to store the discharged energy. The battery charge/discharge power supply apparatus for performing a charge/discharge operation on a storage battery includes a direct current (DC) power source switchably connected to a storage battery, an auxiliary battery switchably connected to the storage battery, and a converter provided between the storage battery and the auxiliary battery, wherein the storage battery is charged with the electric power supplied from the auxiliary battery through the converter in a charge cycle of the storage battery and the auxiliary battery is charged with the electric power discharged from the storage battery through the converter in a discharge cycle of the storage battery.
In this arrangement of the present invention, the power discharged by the storage battery is stored in the auxiliary battery through the converter. In the charge cycle of the storage battery, the power stored in the auxiliary battery is used to charge the storage battery through the converter, thereby recycling the electric energy.
In order to effectively utilize the auxiliary battery and maintain its initial performance for a long period of time, the charge and discharge performances of the batteries are monitored and controlled. For example, it is monitored and controlled as to whether the electric power discharged by the storage battery is appropriately supplied to the auxiliary battery and/or discharge load. Under the control as described above, the storage battery is charged with the discharged electricity of the auxiliary battery and/or the direct current of the DC power source. Also, the auxiliary battery is charged with the discharged electricity of the storage battery and/or the electricity supplied from the direct current source.
The charge and discharge conditions of the storage battery and the auxiliary battery are controlled by measuring the electric current and voltage of the batteries by the current/voltage measuring unit connected to each battery and comparing these measured values and the predetermined values. The comparison operation is performed by a controller such as a micro-computer. Based on the result of the comparison operation, switching between the input-output routes of the converter, switching between the direct current source and the discharge load, and switching of an electric charge source to the auxiliary battery are respectively controlled.
As the auxiliary battery in the power supply apparatus of the present invention, a lead storage battery, Ni—Cd (nickel cadmium) storage battery, Ni—MH (nickel metal-hydride) storage battery or Li-ion (lithium ion) storage battery may be used. Considering the function of the converter, the same kind of batteries should be used for both the storage battery and the auxiliary storage battery. The converter is typically a DC-DC converter which adjusts the voltage difference between the storage battery and the auxiliary battery. The converter also functions as a buffer for transferring the electric power from one battery to the other.
The capacity of the auxiliary battery may be freely determined. However, if the depth of discharge is increased to more than 80%, the durability of the auxiliary battery is greatly deteriorated and eventually the battery's life will end. Therefore, the depth of discharge in the auxiliary battery should be maintained 80% or less, preferably in the range from 25% to 50%.
The battery charge/discharge power supply apparatus as described above functions in such a way that the storage battery to be activated or tested is charged with electric energy which is stored in the auxiliary battery, and the auxiliary battery is charged with the electric energy of the storage battery which had been charged with the electricity discharged by the auxiliary battery. By this energy recycling in the battery charge/discharge power supply apparatus of the present invention, a large amount of energy saving can be achieved.
REFERENCES:
patent: 5254929 (1993-10-01), Yan
Muramatsu & Associates
Toyo System Co., Ltd.
Tso Edward H.
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