Method of and circuit for Ni-Cd battery charge control
First Claim
1. Method of charge control for Ni-Cd batteries, which are used in particular on a low earth orbit spacecraft, wherein said batteries are subjected to high speed charge and discharge cycles, a typical cycle lasting 1.5 hours, the individual battery cells of which are electrically isolated by means of a thermally conductive material with thin metal plates between the isolated battery cells fixed to a common metal base plate, which method comprises the steps of:
- sensing battery temperature at the location of said thin metal plates by means of suitable temperature sensors, andterminating battery charge by detecting a change of sign of the first derivative of the battery temperature thus sensed, when this temperature derivative becomes positive following its negative value during charge.
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Abstract
Method of and circuit for Ni-Cd battery charge control, particularly on low earth orbit spacecraft, according to which battery charge is terminated when the battery temperature starts to increase following a decrease at the end of charge. The temperature of the battery is sensed at individual cell level by means of thermistors placed preferably at the geometric center of thin metal plates between the isolated cells, these plates being fixed to a common metal base plate.
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Citations
7 Claims
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1. Method of charge control for Ni-Cd batteries, which are used in particular on a low earth orbit spacecraft, wherein said batteries are subjected to high speed charge and discharge cycles, a typical cycle lasting 1.5 hours, the individual battery cells of which are electrically isolated by means of a thermally conductive material with thin metal plates between the isolated battery cells fixed to a common metal base plate, which method comprises the steps of:
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sensing battery temperature at the location of said thin metal plates by means of suitable temperature sensors, and terminating battery charge by detecting a change of sign of the first derivative of the battery temperature thus sensed, when this temperature derivative becomes positive following its negative value during charge. - View Dependent Claims (2)
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- 3. Circuit for charge control of Ni-Cd batteries used in particular on a low earth orbit spacecraft, wherein said batteries are subjected to high speed charge and discharge cycles, a typical cycle lasting 1.5 hours, said circuit allowing said batteries to be charged by solar array means during the sunlight period of said spacecraft when a switch S of this circuit is closed and said batteries having the individual battery cells electrically isolated by means of a thermally conductive material with thin metal plates between the isolated battery cells fixed to a common metal base plate, said circuit comprising end-of-charge detector means which detect a change of sign of the first derivative of the battery temperature, when this temperature derivative becomes positive following its negative value during charge, and which provide a signal to open said switch S which stays open for the remainder of the sunlight period, the battery temperature being sensed by suitable sensor means, placed at the location of said thin plates.
Specification