Method and device for estimating charge/discharge electricity amount of secondary cell

Abstract

When a particular selection condition is satisfied, a no-load voltage calculation section (105) calculates a no-load voltage Vsep which is a voltage piece when the current in the approximate straight line obtained by statistical processing is zero for a plurality of set data consisting of current data I(n) and voltage data V(n). Moreover, when a particular current condition is satisfied continuously for a certain time, a release voltage calculation section (106) calculates the terminal voltage of the secondary cell as a release voltage Voc. By using a preset voltage change amount adjustment constant DeltaVbc, an adjustment coefficient Kb, an electromotive force change constant Keq, and a polarization voltage generation constant Kpol, an estimated charge / discharge electricity amount calculation section (114) calculates an estimated charge / discharge electricity amount DeltaQe as a function of a no-load voltage in a predetermined period or a release voltage change amount DeltaVb.

Description

technical field [0001] The present invention relates to estimating the residual battery life of a secondary battery such as a nickel-hydrogen (Ni-MH) battery mounted as a power source of a motor or a driving source of various loads in an electric vehicle (PEV) or a hybrid vehicle (HEV). Capacity (SOC: State of Charge) technology. Background technique [0002] Conventionally, in HEVs, the voltage, current, temperature, etc. of the secondary battery are detected, and the remaining capacity of the secondary battery (hereinafter, abbreviated as SOC) is estimated by calculation, and the SOC control is performed to optimize the fuel consumption efficiency of the vehicle. it is good. In order to accurately control the SOC, it is necessary to accurately estimate the SOC of the secondary battery being charged and discharged. [0003] As such a conventional SOC estimation method, there is the following method: First, measure the battery voltage V and the charged and discharged curre...

AI Technical Summary

Problems solved by technology

When this current sensor is used in HEV, etc., it is necessary to measure a large current, and the cost increases when a high-precision current sensor is used, so the actual situation is that a low-cost and low-precision current sensor has to be used.

Therefore, a measurement error is included in the current value detected by the current sensor, and this current error becomes an estimation error of SOC

Especially when the charge-discharge rate is smaller than the current error (for example, for a charge-discharge rate of 1A, there is a current error of ±2A, etc.), the operating conditions of the estimated SOC change significantly with the passage of time. Difference

[0006] In addition, as in the above conventional example, as a function of the integral value of the current measured by such a current sensor, the polarization voltage Vc(t-1) of the battery estimated last time is updated to Vc(t), and In the method of estimating the SOC in consideration of the influence of the polarization voltage, a current error is included in the calculation of the past polarization voltage, and this current error becomes an estimation error of the polarization voltage. The problem that the actual value of SOC and the error of the estimated value increase

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