State-of-charge indicator for zinc-mercuric oxide primary cells
First Claim
1. The method of determining the state-of-charge of zinc-mercuric oxide type primary cells comprising the steps ofdischarging new cells of said type at selected different rates to produce a plurality of discharged new cells of known state-of-charge value,graphically producing a mean linear curve by plotting the effective differential DC resistance value of each of said discharged new cells versus the said known state-of-charge value,determining the effective differential DC resistance of a used cell whose state-of-charge is to be determined,and locating on said mean linear curve the state-of-charge value corresponding to said used cell effective differential DC resistance, said corresponding value indicating the state-of-charge of said used cell.
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Abstract
A method for determining the state-of-charge for zinc mercuric oxide type primary cells. I-V curves of the cells are plotted and the nearly constant slopes of these I-V curves above 75mA are measured graphically. These slopes are used to define effective differential DC resistance values (ΔV/ΔI)75mA which have a linear relationship to charge expended, Q(A-h), which is graphically produced by plotting (ΔV/ΔI)75mA versus Q(A-h). This relationship is used as a basis for a state-of-charge indicator to determine the remaining charge to about 12%. One can also subtract the internal resistance of the cell (measured with an a-c bridge technique) from (ΔV/ΔI)75mA and obtain a new parameter, Rp, which is related to the polarization resistance of the cell. The maximum uncertainty can be reduced to less than 10% if the linear curve is produced by plotting polarization resistance Rp of the cell versus the charge expended Q(A-h). More significantly, the polarization based state-of-charge graph is linear out to 100% of discharge and is applicable to cells discharged at abnormally high current.
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Citations
7 Claims
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1. The method of determining the state-of-charge of zinc-mercuric oxide type primary cells comprising the steps of
discharging new cells of said type at selected different rates to produce a plurality of discharged new cells of known state-of-charge value, graphically producing a mean linear curve by plotting the effective differential DC resistance value of each of said discharged new cells versus the said known state-of-charge value, determining the effective differential DC resistance of a used cell whose state-of-charge is to be determined, and locating on said mean linear curve the state-of-charge value corresponding to said used cell effective differential DC resistance, said corresponding value indicating the state-of-charge of said used cell.
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4. The method of determining the state-of-charge of zinc-mercuric oxide type primary cells comprising the steps of
discharging new cells of said type at selected different rates to produce a plurality of discharged new cells of known state-of-charge value, graphically producing a mean linear curve by plotting the effective polarization resistance value of each of said discharged new cells versus the said known state-of-charge value, determining the effective polarization resistance of a used cell whose state-of-charge is to be determined, and locating on said mean linear curve the state-of-charge value corresponding to said used cell effective polarization resistance, said corresponding value indicating the state-of-charge level of said used cell.
Specification