| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect an over discharge state and/or an over charge state of a secondary battery to be estimated, by providing at least one set of discharge pulse and charge pulse and discriminating a battery state based on the responses. SOLUTION: At least one set of discharge and charge pulses is added to a secondary battery 33 to be measured from a constant current pulse generating means 38. A voltage measuring portion 34 measures voltage of voltage pulses corresponding to the discharge and charge pulses, adds it to a peak-hold circuit 35, and detects peak-hold voltage. A calculation-determining portion 36 determines a charge state with reference to the peak-hold voltage and a threshold voltage from a threshold voltage-generating portion 37. H is determined when the peak-hold voltage is higher than the threshold voltage for 0.02-10 sec pulse maintaining period, and L is determined when it is lower. When a combination of discharge voltage (x) and charge voltage (y) is set (x, y), (L, H) shows over charge, (L, L) shows normal state, and (H, H) shows over discharge. Degradation of the secondary battery can be determined in a simple structure.
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