Nissan Motor Company Limited

Yuji Nakada

Takeshi Miyamoto

Tsuyoshi Morita

Takeshi Hirata

Tsuyoshi Yamanaka

Tomonaga Sugimoto

Utaka Kamishima

Kenichi Sakai

Norihiko Hirata

A state of charge of a battery () that drives a motor () is computed based on a discharge current measured by a current sensor () when the discharge current of the battery () does not exceed a rated discharge range of the battery (). When the discharge current of the battery () exceeds the rated discharge range, the state of charge of the battery () is computed by estimating the discharge current of the battery () from a motor control signal, whereby current changes over a wide range can be found with good precision using the sensor (), which has a narrow but high resolution measurable range, and the state of charge can be accurately detected.

Battery state of charge detection

A plurality of single cellstoeach being packaged by laminate filmsandare attached onto one surface of a flexible printed circuit boardin a state of being interconnected in series to each other, by the use of a double faced tape. Single cells' to&#x2032; are attached in a similar way onto the other surface of the flexible printed circuit boardEach group of the cells on the both surfaces of the flexible printed circuit boardare interconnected in parallel. Voltage detection linestoare wired on the flexible printed circuit boardPositive and negative electrode tabsandof the respective single cells are connected to the respectively corresponding voltage detection linestothrough connection terminalstoprovided on the flexible printed circuit board

Cell assembly

If the voltage at any cell has become equal to or lower than a low-voltage decision-making voltage Vcand the average voltage among cells calculated based upon the total voltage at a battery cell is higher than a predetermined voltage level, it is determined that a voltage variance among the individual cells has occurred and that a capacity adjustment is necessary.

Capacity adjustment apparatus for battery pack and capacity adjustment method for battery pack

A bypass engaging voltage is set to a relatively high value and a target charging rate for a capacity adjustment is set higher than the target charging rate set in a regular charge/discharge mode when executing the capacity adjustment for individual cells by employing capacity adjustment circuits that discharge the corresponding cells when their voltages exceed the specific bypass engaging voltage.

A battery pack of a series combination of cell units is connected with a motor drive control circuit to drive a traction motor for a vehicle. A current sensor senses a discharge/charge current of the battery pack, and a voltage detecting circuit senses a voltage between two separate points in the series combination of the battery pack. A memory section stores a reference voltage drop quantity representing a decrease in voltage during a predetermined time interval between the two separate points. An offset detecting section compares an actual voltage drop quantity sensed by the voltage detecting circuit, with the reference voltage drop quantity, thereby detects a non-discharge/charge-current state of the current sensor, and reserves an output of the current sensor, as an offset quantity upon the detection. A correcting section corrects a sensed value of the discharge/charge current with the reserved offset quantity.

Control for battery pack

A battery pack capacity adjustment apparatus, which is installed in a vehicle, executes capacity adjustment for a plurality of cells constituting a battery pack by raising the target charging rate for the battery pack from a first target charging rate to a second target charging rate when a voltage variance abnormality among the plurality of cells is detected and the currently traveling vehicle is predicted to stop.

A capacity indicating device is configured to indicate a fully charged state when full recharging has been conducted even if the battery is degraded; hold the possible traveling distance per segment roughly constant; and make it easy to estimate the possible cruising distance. The capacity indicating device has an indication control unit that: (1) allocates a prescribed portion of the battery capacity of a vehicle to a capacity adjustment region that serves to adjust the battery capacity as it decreases due to degradation of the battery; (2) calculates the degradation degree of the battery based on the detected voltage value and current value; (3) corrects the capacity adjustment region a based on the calculated degradation degree; and (4) indicates the present battery capacity using segments that are not affected by the degradation of the battery.

Growing community of inventors

Tokyo, Japan

Yuji Nakada