Electricity: battery or capacitor charging or discharging – Capacitor charging or discharging
Reexamination Certificate
2003-06-10
2004-12-28
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Capacitor charging or discharging
Reexamination Certificate
active
06836098
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
In general, this invention relates to battery chargers, and more particularly to a method of charging a secondary battery or string of batteries by the use of pulses of direct current, as opposed to continuous current, specifically where a repeated step in enactment of the method involves pulsed discharges of current taken from the battery or batteries string, interspersing such discharging pulses between charging pulses. Another aspect of general pertinence concerns timely switching back and forth between parallel aud series arrangements of circuitry. Types of batteries chargeable in accordance with the method to be described may include, but are not confined to, batteries having magnetized current collectors, such as those described in U.S. Pat. No. 6,194,093 B1 by O'Brien, the same inventor as at present.
BACKGROUND OF THE INVENTION
2. Description of Related Art
Descriptions of battery chargers delivering charging current pulses interspersed by pulsed battery discharges are extant, including chargers devised to procure depolarization of batteries by means of the discharges. Such depolarization mitigates adverse consequences of high current rapid charging, including elevated internal energy losses, overheating, and gas evolution dangerously building up pressure within battery casings. In background discussion for U.S. Pat. No. 4,829,225 by Podrazhansky et al., earlier implementation of a reversedly pulsing approach to battery charging was credited to others, eg., Burkett et al.
U.S. Pat. No. 4,829,225 particularly teaches “charging a battery by providing a charge pulse to the battery, followed immediately by a depolarization pulse created by allowing the battery to discharge across a load, followed by a stabilization period, and repeating this sequence cyclically until the battery is charged.” The same patent also suggests that the “discharge load may be provided by a transistor . . . controlled by the system control logic . . . to provide a variable resistance.” There is ill suggestion by Podrazhansky et al. that the component loaded by discharge pulses should be a supercapacitor—preferably employing the new supercapacitors with magnetized parts that O'Brien describes in U.S. Pat. No. 6,556,424 B2 which is herewith incorporated by reference.
In general, one kind of distinction thought helpful for distinguishing between the reversedly pulsing (charging/discharging) arrangements of some inventions in this field, from others, is the distinction concerning the specific type of component or locally grouped set of components to which discharge pulses from a battery or, batteries string are to be delivered. Thus, on the point that discharges are delivered to a variable-resistance transistor for the Podrazhansky et al battery charger, more of a family resemblance thereto than strong distinction therefrom is perceptible in the pulsed charger described in U.S. Pat. No. 5,621,297 by Feldstein, who discloses means whereby discharge pulses flow through “isolation diodes” to “discharge current resistors”, as and when permitted by transistorized control. Podrazhansky et al and Feldstein therefore would likely concur in accepting the inevitable energy losses associated with delivering battery current to resistors. Acceptance of degradation of electric energy to heat is not part of the approach adopted for the present invention, however, albeit also involves interspersal of battery current discharge pulses between battery charging pulses.
Another approach perceptible in the background art is to locally group inductors and ordinary capacitors in suitably switched circuitry, so as to use a subset of inductors and capacitors both to discharge pulses of charging current into a battery or batteries string, and to intermittently receive pulses of battery current discharged thereto. This approach seems to use inductors and capacitors, basically, in substitution for the kind of use of resistors as has been mentioned above with regard to the Podrazhansky et al and Feldstein inventions. Both W. Newman in U.S. Pat. No. 4,016,473 and Pascual et al in U.S. Pat. No. 5,710,504 describe using inductors and capacitors grouped to intermittently receive delivery of battery discharge pulses.
When current flowing through an inductor is switched off, there will of course occur a collapsing magnetic field, causing dissipation of heat in local conductors, which is as truly an instance of energy degradation as is that occurring with components more ostensibly identified as resistors. The difference that resistors generate heat during the period of time when current is flowing, whereas inductors generate heat immediately after flowing current is interrupted, is not of significance to the point presently made, that the substitution for resistors that appears adopted by Newman and by Pascual et al incurs energy loss because of switching off inductors. Moreover, neither Newman nor Pascual et al specify a requirement that the capacitors they use to both transmit and receive pulsed current should be supercapacitors, as specified hereinafter as an essential feature of the present invention.
The abovecited Pascual et al. invention, which does not in every embodiment require using inductors to the same extent Newman uses them, is ostensibly concerned with art “active equalization” method whereby batteries in a long string way be equalized. The inference is not avoidable, however, that an incidental effect of the method of equalization proposed by Pascual et al. is depolarization procured in a substantially similar manner as for the several battery charger patents of the background art.
The practice of discharging depolarization pulses from a battery by use of a special charger is applicable to secondary electrochemical cells of well known types having solid-phase electroactive materials for anodes and cathodes, in contact with liquid-phase, usually aqueous, electrolyte solutions, noting that such cells operate at temperatures below melting points of the electroactive materials involved. High temperature cells using electroactive materials such as sodium and sulfur in a molten flowing state do not incur the identical entire set of problems addressed by pulsed charging methods, including, for example, the battery life cycle problem of shedding of electroactive materials from typical metal electrode grids or current collectors, which can occur due to the difference in thermal expansion properties between the grids and/or current collectors on the one hand, and the electroactive materials on the other hand. The present invention applies to the same types of batteries as do the background art inventions, and like them helps prolong battery life cycles by avoiding the high continuous current method of charging that exacerbates a tendency of overheated electrode assemblies to shed electroactive materials.
BRIEF SUMMARY OF THE INVENTION
Objects of this invention include providing an improved method and apparatus for rapidly charging an electrically rechargeable battery or batteries string by a series of charging pulses, interspersed with battery discharge pulses effective to eliminate undesired concentration polarization, by substantially thinning or dispelling electrical double layers and diffusion layers at electrodes contacted by an aqueous electrolyte solution. Concurrent objects include prevention of overheating batteries, and of dangerously built-up pressure from gas evolution. A major general aim is to conserve energy in the course of enacting intermittent discharge pulses interspersed with charging pulses. An important specific object of invention is to effect discharge pulses in such a manner that electrical energy is not degraded to heat energy either by dissipation in resistive elements or in consequence of magnetic field collapses when local currents suddenly cease. Electrical energy of discharge pulses is to be stored temporarily in supercapacitors that will experience no significant heating during their service in accordance with the method of the invention.
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