Patent ID: 7190171

Claim:
A detecting method for detecting internal resistance of an inspective rechargeable battery when said inspective rechargeable battery is charged by a constant current-constant voltage charging regime comprising a constant current charging mode and a constant voltage charging mode in that charging is commenced by said constant current charging mode at a constant current value I 0 and after the battery voltage of said inspective rechargeable battery reaches a given voltage value V max , the charging is performed by said constant voltage charging mode at a constant voltage V max until the termination thereof, said detecting method comprising the steps of: (a) obtaining an accumulated, charged electricity quantity of said inspective rechargeable battery in said constant voltage charging mode; and (b) comparing said charged electricity quantity obtained in said step (a) to previously acquired data of a normal rechargeable battery in said constant voltage charging mode, said normal rechargeable battery corresponding to said inspective rechargeable battery, wherein said previously acquired data are with respect to relationships between charged electricity quantities Q cv of said normal rechargeable battery and increased or decreased internal resistances of said normal rechargeable battery or between said charged electricity quantities Q cv and increased or decreased magnitudes of said internal resistances, wherein when said inspective rechargeable battery has an electricity storable capacity which is reduced to a magnitude of D time that of said normal rechargeable battery, where D is a constant of 0<D≦1, said detecting method further includes a step of correcting said charged electricity quantity obtained in said step (a) by multiplying said charged electricity quantity by 1/D time, wherein the corrected electrical quantity is compared to said previously acquired data of said normal rechargeable battery described in said step (b), and wherein in a case where it is presumed that said electricity storable capacity of said inspective rechargeable battery is reduced to a magnitude of D time that of said normal rechargeable battery, when a duration from a shift time when said constant current charging mode at said constant current value I 0 is shifted to said constant voltage charging mode at said constant voltage V max until a time when the charging current value in said constant voltage charging mode reaches a prescribed current value I M and an electricity quantity charged in said constant voltage charging mode are made to be respectively t M ′ and Q cv ′ for said inspective rechargeable battery and t M and Q cv for said normal rechargeable battery, in accordance with a function formula D=(Q cv ′−I 0 ×t M ′)/(Q cv −I 0 ×t M ), said electricity storable capacity of said inspective rechargeable battery is estimated to be D time that of said normal rechargeable battery.