NICAD Deep Cycle Charging/Discharging System
Patent, Filed 30 Sep 96, patented 7 Jul 98
DEPARTMENT OF THE NAVY WASHINGTON DC
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A chargingdischarging apparatus uses constant charging current and constant discharging current to reduce the possibility of building memory in the cells of a battery. Memory reduces battery capacity and eventual failure will result since the cells will refuse to take any charge. A charger circuit includes a current source receiving supply voltage to couple constant charging current to the battery and an amplifier is coupled to receive reference voltage from a source and feedback voltage from the battery to connect supply voltage to the current source when the reference voltage is greater than the feedback voltage. A discharger circuit utilizes a current sink receiving supply voltage to couple constant discharging current to the battery. An amplifier receives reference voltage from a source and feedback voltage from the battery to connect supply voltage to the current sink when the reference voltage is less than the feedback voltage. In both charger and discharger applications the current source or current sink maintains a constant current to the battery independently of the magnitude of voltage of the battery. This use of constant current does not rely on battery voltage to charge the cell and can discharge a cell well below the minimum operating voltage. The apparatus is particularly adaptable to recharge NiCad batteries which require specific conditions to properly charge and deep-cycle discharge for maximum life.
- Electrochemical Energy Storage