Method for predicting the equilibrated open-circuit voltage of an electrochemical energy store
First Claim
1. A method for predicting an equilibrated open-circuit voltage of an electrochemical storage battery comprising measuring a voltage settling response Uo(t) in a load-free period using a relationship (1) between an equilibrated open-circuit voltage Uoo and a decaying voltage Uo(t)Uoo=Uo(t)−
-
w*ln(t)−
w*F(T)
(1),wherein w is an experimentally determined slope of dependency of Uo on ln(t) at time t, w=−
(Uo(t2)−
Uo(t1))/ln(t2/t1), Uo(t1) is an unloaded voltage Uo at time t1, Uo(t2) is an unloaded voltage Uo at later time t2>
t1, and F(T) is a function which depends only on absolute temperature T of the battery.
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Abstract
In a method for predicting the equilibrated open-circuit voltage of an electrochemical energy store by measuring the voltage settling response Uo(t) in a load-free period, a formulaic relationship between the equilibrated open-circuit voltage Uoo and the decaying voltage Uo(t) of the form Uoo=Uo(t)−w*ln(t)−w*F(T) is used, the prefactor w being the experimentally determined slope of the dependency of Uo on ln(t) at the time t, w=−(uo(t2)−Uo(t1))/ln(t2/t1), and Uo(t1) being the unloaded voltage Uo at the time t1 and Uo(t2) being the unloaded voltage Uo at the later time t2>t1, and F(T) being a function which depends only on the absolute temperature T of the energy store. The function F(T) has the general form F(T)=(K|E/T)/(1+q*w)/f(T), K, E and q being experimentally determined constants, T being the absolute temperature in kelvin, and f(T) being a function which contains only the absolute temperature T as a free parameter.
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Citations
14 Claims
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1. A method for predicting an equilibrated open-circuit voltage of an electrochemical storage battery comprising measuring a voltage settling response Uo(t) in a load-free period using a relationship (1) between an equilibrated open-circuit voltage Uoo and a decaying voltage Uo(t)
Uoo=Uo(t)− -
w*ln(t)−
w*F(T)
(1),wherein w is an experimentally determined slope of dependency of Uo on ln(t) at time t, w=−
(Uo(t2)−
Uo(t1))/ln(t2/t1), Uo(t1) is an unloaded voltage Uo at time t1, Uo(t2) is an unloaded voltage Uo at later time t2>
t1, and F(T) is a function which depends only on absolute temperature T of the battery.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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12. The method as claimed in claim 11, wherein the battery is a lead-acid battery, and constant û
- for an individual battery cell has a value of approximately 0.002 V to approximately 0.02 V, at 25°
C., and a value of approximately 0.003 V to approximately 0.03 V, at −
20°
C., and is linearly interpolated or extrapolated for other temperatures.
- for an individual battery cell has a value of approximately 0.002 V to approximately 0.02 V, at 25°
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13. The method as claimed in claim 12, wherein constant û
- is about 0.007 V at 25°
C. and about 0.01 V at −
20°
C.
- is about 0.007 V at 25°
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14. A method of predicting state of charge comprising:
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measuring the voltage settling response of the storage battery according to the method of claim 1;
andcomparing the voltage settling response to true open-circuit voltage Uoo and the decay voltage Uo(t) to determine the state of charge.
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w*ln(t)−
Specification