Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Patent
1997-01-29
1998-09-29
Tso, Edward
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
320119, 320122, H01M 1046
Patent
active
058149708
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an apparatus for charge exchange among a plurality of like energy accumulators or energy converters wired in series and forming an overall energy accumulator, in which apparatus electric accumulators consisting each of a capacitive element charged from the energy accumulators are with the aid of switches that are activated by a clock generator wired in parallel with one each of the like energy accumulators or energy converters, so that all of the like energy accumulators or energy converters are in at least one cycle wired, each individually, in parallel with a capacitive element.
Such an apparatus is known from the document DE 39 40 929 of the applicant. On that apparatus, two energy accumulators each, of the plurality of energy accumulators, are with the aid of a power multiplexer connected to a capacitor, whereby a charge equalization can take place between the two selected energy accumulators. Disadvantageous is here that always only two energy accumulators can be processed, each of the connected accumulators being connected to the equalizing capacitor less than 50 percent of the total time. In an incidental selection of the energy accumulator, each energy accumulator is with N energy accumulators thus connected to the capacitor for charge equalization only for 1/(2.times.N)th of the time. Improving this system requires an expensive wiring logic. The switches in the prior apparatus must be configured for the entire system voltage.
A similar monitoring method is known from the U.S. Pat. No. 4 331 911 and serves to balance voltages of individual series-wired accumulators, using a DC-DC converter. The electric accumulators are transformer elements. The sole central converter for all accumulators is energized from the overall battery and is incapable of detecting peculiarities of individual accumulators that occur due to ageing.
The document DE-OS 20 21 531 describes an apparatus for extending the discharge time of rechargeable accumulators, where occurring induction currents are by incorporation of a coil in a DC circuit returned again to the current source by way of a capacitor. An extension of the discharge time of the accumulators is effected in that the load is connected to the accumulators at a pulse duty factor that is configured smaller than one. An extension of the service life of accumulators in view of their replacement is not achievable thereby. Specifically, accumulators degrading in their quality cannot be recognized.
Until such an accumulator degrading in its storage and charging quality is recognized by the monitoring system for accumulators, its faulty performance leads to a chain of reactions in the group of accumulators, leading to a degradation of also the other accumulators.
The document DE-PS 30 31 931 describes an apparatus for extending the discharge time of rechargeable accumulators where the voltage states of the accumulators are detected with a monitoring system. An extended, operationally reliable discharge of the accumulators is effected in that the accumulator operation is not ended at discharge, and thus upon reaching a limit voltage of the weakest cell, but only when this limit voltage is reached at the average of all interconnected accumulators. An extension of the service life of accumulators in view of their replacement is not achievable thereby.
Known from SU 1 065 959 is an apparatus for an accumulator charger, which apparatus prevents overcharging and charging at inverted polarity of accumulators. The charging current is monitored by a transistor circuit which additionally comprises zener diodes. This safety circuit, however, can guarantee neither a monitoring of the quality of the accumulators nor bring about a longer service life of accumulators degrading in their quality.
Known from EP 90 123 409 of the applicant is a monitoring system for a plurality of series-wired like accumulators where with the aid of a control circuit an electric accumulator is connected in parallel with one of the accumulators, wherein the primary winding of a transfo
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patent: 5177425 (1993-01-01), Goto
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patent: 5631534 (1997-05-01), Lewis
Heribert Schmidt et al., "The Charge Equalizer-A New System to Extend Baty Lifetime In Photovoltaic Systems, U.P.S. and Electric Vehicles," 15th INTELEC Conference, Paris, France, 1993, pp. 146-151, Sep. 1993.
"Switched Capacitor System for Automatic Series Battery Equalization" by Cesar pascual and Philip T. Krein, APEC '97 Twelfth Annual Applied Power Electronics Conference and Exposition, vol. 2, pp. 848-854.
Fraunhofer-Gesellschaft Zur Forderung der Angewandten Forschung
Tso Edward
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