Zener diode looping element for protecting a battery cell
First Claim
1. A battery system comprising:
- a plurality of battery cells, each having an anode and a cathode connected in series; and
a plurality of zener diode looping elements, each connected in parallel across an associated one of said cells and each looping element including a zener diode p-n junction, and a package formed so that failure of the package will not occur during high current conditions, each said looping element having its cathode connected to the anode of each said cell and said looping element having its anode connected to the cathode of each said cell;
said zener diode looping element being constructed so that when a predetermined amount of current is passed therethrough in a forward biasing direction, said p-n junction fuses permanently into a short circuit state, thereby shorting across said associated battery cell.
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Abstract
A special zener diode is disclosed which is shunted across each cell in a series connected string of battery cells. In response to a cell failure which causes a cell to open circuit, all battery current is routed through the zener diode looping element. This current causes a permanent state change of the looping element thereby causing the looping element to become a permanent short circuit. Thereby, the failed cell is effectively removed from the circuit. Another embodiment is disclosed whereby the zener diodes are used to ensure uniform full charge among all of the cells in the battery. The zener diodes are chosen to have a breakdown voltage slightly higher than the optimal maximum battery voltage. A special charger is used which lowers the charging rate when the zener breakdown voltage is approached, so that the zener will not be destroyed from excess current during charging.
109 Citations
21 Claims
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1. A battery system comprising:
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a plurality of battery cells, each having an anode and a cathode connected in series; and a plurality of zener diode looping elements, each connected in parallel across an associated one of said cells and each looping element including a zener diode p-n junction, and a package formed so that failure of the package will not occur during high current conditions, each said looping element having its cathode connected to the anode of each said cell and said looping element having its anode connected to the cathode of each said cell; said zener diode looping element being constructed so that when a predetermined amount of current is passed therethrough in a forward biasing direction, said p-n junction fuses permanently into a short circuit state, thereby shorting across said associated battery cell. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A battery system comprising:
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terminal means for relaying a voltage from said battery to a load; a plurality of battery cells connected in series between said terminal means; a plurality of zener diodes, each said zener diode connected in parallel across each said battery cell, so that said zener diode is normally reverse biased; and charging means for applying charge to said battery according to a predetermined program;
said predetermined program controlling a current output of said charging means so that when said battery voltage is high enough to cause reverse breakdown of any of said zener diodes, the current emitted from said charging means will be low enough that said zener diodes will not be damaged. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A battery comprising:
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a plurality of battery cells; and a plurality of zener diode looping elements, each cell having a zener diode looping element coupled in parallel therewith so that a cathode of said looping element is coupled to a positive terminal of the battery cell, each said looping element including a zener diode chip packaged so that package failure will not occur during overcurrent conditions, and formed so that a forward current of the battery flowing in a forward direction through said looping element causes said zener diode chip element to permanently fuse into a short circuit state. - View Dependent Claims (17, 18, 19, 20, 21)
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Specification