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| Arrangement for the testing of high voltage direct current switches |
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| Apparatus for detection of rotational angle and number of rotations of a rotary body |
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| Semiconductor switch device |
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| Semiconductor integrated circuit device with a protective circuit |
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Electrochemical storage device
| Details |
Inventors: Maly-Schreiber, Martha; Huggins, Robert A.;
Assignee: Daimler-Benz AG (DE)
Primary Examiner: Gorgos; Kathryn
Assistant Examiner:
Attorney, Agent or Firm: Evenson, McKeown, Edwards & Lenahan P.L.L.C.
The invention relates to an electrochemical storage device having a plurality of serially connected individual cells, each of the individual cells having two spatially separated electrodes, between which an electrolyte and an intermediate part ensuring the spacing of the electrodes is arranged. In the interior of the storage device, each individual cell has a protective element which is formed from a solid material having a nonlinear current/voltage characteristic curve, and which makes electrical contact with the positive and the negative electrode within the individual cell and provides a voltage-dependent electrical connection between said electrodes. The electrical resistance of the protective element above a critical voltage is smaller, and below the critical voltage larger, than the resistance present between the electrodes at the respective voltages without the protective element. To protect the individual cells against overcharging, the critical voltage is smaller than the decomposition voltage of the associated individual cell. |
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DETAILED DESCRIPTION The invention relates to an electrochemical storage device of the type having a plurality of serially connected cells, in which each has two spacially separated electrodes.
German patent document DE 42 29 437 C1 discloses an electrochemical storage device of this generic type, in which a storage device housing surrounding the cells has terminals of differing polarity extending therefrom.
Because of the series connection of the individual cells, the maximum voltage of such a storage device is calculated as the number of individual cells multiplied by their specific voltage.
Thus, these electrochemical storage devices can have a maximum voltage of a few hundreds of volts, and are, therefore, of particular interest for traction batteries for motor vehicles.
Since the components of the individual cells (electrodes, electrolyte, weight of the active masses, distribution etc.
) cannot be manufactured to be completely identical, the individual cells during charging attain their maximum charge state at different times.
If those cells which are already completely charged continue to be subjected to a charge voltage that exceeds the decomposition voltage of the individual components of the individual cells, they may be damaged, or even destroyed.
In the case of electrochemical storage devices having a bipolar sandwich construction (positive electrode, bipolar plate, negative electrode, electrolyte, positive electrode etc.
), this risk is considerable, since the current flows transversely through the thin functional plates or sheets placed next to one another in layers, and the electrodes are not equipped with current collector lugs between which a protective element can be interposed.
Furthermore, appropriate contacting would at least be very complicated, since the thickness of the individual cell elements may be less than 1 mm.
In some cases, the electrolytes and/or the electrodes are even fashioned as a thin sheet.
German patent document DE 28 19 584 C2 discloses a protective circuit for a plurality of electrochemical storage devices connected in series, or sets of electrochemical storage devices connected in parallel, for which each electrochemical storage cell connected in series, and each set of electrochemical storage cells connected in parallel, is assigned a protective element which is arranged from outside and is electrically connected in parallel thereto
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Electrical and Wave 
