Battery system and estimation method of full charge capacity
The threshold cumulative value calculation unit calculates a threshold cumulative value. The current cumulating unit cumulates the charging current. When the first current cumulative value, which is the cumulative value from the start of charging, becomes equal to or larger than the threshold cumulative value, the maximum value detecting unit starts detection of the local maximum value of the amount of change in the voltage. The full charge capacity calculation unit calculates a full charge capacity by adding a first current cumulative value, which is a current cumulative value from when the maximum value is detected to when the full charge is detected, to a reference capacity when the maximum value is detected.
1 . A battery system, comprising a battery; a voltage sensor for configured to detect a voltage of the battery; a current sensor configured to detect a charging current of the battery; and a control device, wherein the control device includes a Central Processing Unit (CPU) configured to:
calculate a threshold value for a cumulative charging current value based on a time from an end time of charging or discharging of the battery at a previous time to a time of starting charging of the battery, a voltage at the time of starting charging, and a temperature of the battery at the time of starting charging;
compute the cumulative charging current value that is a cumulative value of the charging current of the battery,
compare a first cumulative current value, which is the cumulative charging current value from the start of charging of the battery, with the threshold value, and determine whether the first cumulative current value exceeds the threshold value;
detect a maximum value of a voltage change amount when charging the battery, based on the voltage,
wherein the CPU is configured to detect the maximum value of the voltage change amount only after the first cumulative current value becomes equal to or greater than the threshold value, the maximum value being detected on a side of the battery at which voltage is high; and
estimate a full charge capacity of the battery, based on a second cumulative current value that is the cumulative charging current value from when the maximum value is detected until the battery is fully charged.
2 . The battery system according to claim 1 , wherein the CPU is configured to calculate the full charge capacity by adding the second cumulative current value to a reference capacity that is set in advance.
3 . The battery system according to claim 1 , wherein the CPU is further configured to
stop charging of the battery and, calculate an offset value of the current sensor in response to detecting the maximum value.
4 . An estimation method of estimating a full charge capacity of a battery, the estimation method comprising:
calculating a threshold value of a cumulative charging current value based on a time from an end time of charging or discharging of the battery at a previous time to a time of starting charging of the battery, a voltage at the time of starting charging, and a temperature of the battery at the time of starting charging;
computing the cumulative charging current value that is a cumulative value of a charging current of the battery;
comparing a first cumulative current value, which is the cumulative charging current value from a start of charging of the battery, with the threshold value, and determining whether the first cumulative current value is equal to or greater than the threshold value;
detecting a maximum value of a voltage change amount of the battery only after the first cumulative current value becomes equal to or greater than the threshold value; the maximum value being detected on a side of the battery at which voltage is high;
calculating a second cumulative current value that is the cumulative charging current value from when the maximum value is detected until the battery is fully charged; and
estimating the full charge capacity of the battery based on the second cumulative current value.