Determining the state of-charge of batteries via selective sampling of extrapolated open circuit voltage
First Claim
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1. A method of determining a state-of-charge of a battery within a system powered at least in part by the battery comprising:
- collecting a plurality of voltage measurements from the battery during operation of the system;
deriving a time-constant of relaxation and an open-circuit voltage corresponding to the battery from the voltage measurements and a mathematical model of the battery that relates the voltage measurements to the open-circuit voltage and the time-constant of relaxation; and
,estimating the state-of-charge of the battery based, at least in part, on the open-circuit voltage;
wherein the mathematical model comprises a closed mathematical expression that includes the open-circuit voltage and the time-constant of relaxation; and
,wherein the closed mathematical expression is of the form;
V(t)=OCV−
α
et/τ
, wherein V(t) is one of the voltage measurements at a given point in time, OCV is the open-circuit voltage, α
is an overpotential, and τ
is the time-constant of relaxation.
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Abstract
A method for estimating the state-of-charge of a battery. The method includes collecting a plurality of voltage measurements during operation of the system containing the battery and determining a time-constant of relaxation and an open-circuit voltage corresponding to the battery based, at least in part, on the voltage measurements. The method further includes estimating the state-of-charge of the battery based, at least in part, on the open-circuit voltage.
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Citations
20 Claims
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1. A method of determining a state-of-charge of a battery within a system powered at least in part by the battery comprising:
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collecting a plurality of voltage measurements from the battery during operation of the system; deriving a time-constant of relaxation and an open-circuit voltage corresponding to the battery from the voltage measurements and a mathematical model of the battery that relates the voltage measurements to the open-circuit voltage and the time-constant of relaxation; and
,estimating the state-of-charge of the battery based, at least in part, on the open-circuit voltage; wherein the mathematical model comprises a closed mathematical expression that includes the open-circuit voltage and the time-constant of relaxation; and
,wherein the closed mathematical expression is of the form;
V(t)=OCV−
α
et/τ
, wherein V(t) is one of the voltage measurements at a given point in time, OCV is the open-circuit voltage, α
is an overpotential, and τ
is the time-constant of relaxation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of operation within a system powered at least in part by a battery, the method comprising:
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collecting a plurality of voltage measurements of the battery over a first time interval and during operation of the system, wherein the plurality of voltage measurements are to be used to estimate a state-of-charge of the battery; adjusting a time-constant value based on the plurality of voltage measurements collected over the first time interval, the time-constant value indicating a rate at which the battery voltage transitions from a voltage under load to an open-circuit voltage; and adjusting the duration of the first time interval based at least in part on the time-constant value; wherein adjusting the time-constant value comprises regressing the time-constant value using the function V(t)=OCV−
α
et/τ
, wherein V(t) is one of the voltage measurements at a given point in time within a regression interval, OCV is the open-circuit voltage, α
is an overpotential, and τ
is the time-constant value. - View Dependent Claims (12)
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13. A system powered at least in part by a battery, the system comprising:
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voltage measurement circuitry coupled to the battery to generate a plurality of measurements of the battery voltage during operation of the system; battery management circuitry coupled to the voltage measurement circuitry, the battery management circuitry configured to determine a time-constant of relaxation and an open-circuit voltage for the battery from (i) the plurality of measurements of the battery voltage and (ii) a mathematical model of the battery that relates the battery voltage to the open-circuit voltage and the time-constant of relaxation; and estimating a state-of-charge of the battery based, at least in part, on the open-circuit voltage; wherein the mathematical model comprises a closed mathematical expression that includes the open-circuit voltage and the time-constant of relaxation; and
,wherein the closed mathematical expression is of the form;
V(t)=OCV−
α
et/τ
, wherein V(t) is one of the voltage measurements at a given point in time, OCV is the open-circuit voltage, α
is an overpotential, and τ
is the time-constant of relaxation. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification