Optical state-of-charge monitor for batteries
First Claim
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1. A system for determining the state-of-charge of a battery having a conductor that changes in chemical composition with discharge, comprising:
- a means for emitting light at a pre-determined wavelength and a pre-determined pathlength into the conductor, wherein said predetermined wavelength is chosen from a plot of the absorption coefficient of the conductor versus a plurality of wavelengths at a chosen limit of the chemical composition of the conductor and said pre-determined pathlength is chosen to correspond to said pre-determined wavelength and the transparency of the conductor;
a means for optically interrogating the conductor to obtain optical absorption at said pre-determined wavelength, the optical absorption varying with the changes in chemical composition in the conductor with discharge;
a means for detecting the varying optical absorption in the conductor, said detecting means being operably connected to said optically interrogating means;
a means for converting the detected optical absorption to state-of-charge information capable of being read by a user of the battery; and
a means for displaying the state-of-charge information to the user of the battery.
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Abstract
A method and apparatus for determining the instantaneous state-of-charge of a battery in which change in composition with discharge manifests itself as a change in optical absorption. In a lead-acid battery, the sensor comprises a fiber optic system with an absorption cell or, alternatively, an optical fiber woven into an absorbed-glass-mat battery. In a lithium-ion battery, the sensor comprises fiber optics for introducing light into the anode to monitor absorption when lithium ions are introduced.
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Citations
37 Claims
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1. A system for determining the state-of-charge of a battery having a conductor that changes in chemical composition with discharge, comprising:
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a means for emitting light at a pre-determined wavelength and a pre-determined pathlength into the conductor, wherein said predetermined wavelength is chosen from a plot of the absorption coefficient of the conductor versus a plurality of wavelengths at a chosen limit of the chemical composition of the conductor and said pre-determined pathlength is chosen to correspond to said pre-determined wavelength and the transparency of the conductor; a means for optically interrogating the conductor to obtain optical absorption at said pre-determined wavelength, the optical absorption varying with the changes in chemical composition in the conductor with discharge; a means for detecting the varying optical absorption in the conductor, said detecting means being operably connected to said optically interrogating means; a means for converting the detected optical absorption to state-of-charge information capable of being read by a user of the battery; and a means for displaying the state-of-charge information to the user of the battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for determining the state-of-charge of a battery having a conductor that changes in chemical composition with discharge, comprising the steps of:
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choosing a wavelength from a plot of the absorption coefficient of the conductor versus a plurality of wavelengths; choosing a pathlength to correspond to said pre-determined wavelength and the transparency of the conductor; emitting light at the pre-determined wavelength and the pre-determined pathlength into the conductor; optically interrogating the conductor to obtain changes in absorption in the conductor during discharge of the battery, the changes in absorption being manifested as changes in optical power in the light; detecting the optical power changes; converting the optical power changes to state-of-charge information communicable to a user of the battery; and displaying the state-of-charge information to the user of the battery. - View Dependent Claims (29, 30, 31, 32, 33, 35, 36, 37)
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34. The method of 33, wherein said at least two pre-determined wavelengths are chosen to provide absorption coefficients having the same additive temperature correction, and said calculating step further comprises the step of subtracting optical signals obtained at said two pre-determined wavelengths, thereby canceling the temperature dependence and providing a temperature-independent optical signal.
Specification