Battery remaining power predicting device and battery pack
View Patent ↗To provide a battery pack capable of performing a highly accurate prediction of a remaining power of a battery while being low in cost. A battery remaining power predicting device includes a voltage detection portion which measures a voltage and a temperature of a battery, a computing portion which predicts and calculates a remaining power of the battery, and a controller which controls the computing portion, and has a battery remaining power predicting flow for regressively calculating the battery remaining power, and a secular change estimating flow for estimating a secular change in battery characteristics, using a case where a battery current is in a constant current state.
1. A battery remaining power predicting device configured to measure a voltage and a temperature of a rechargeable battery and to predict a remaining power of the rechargeable battery, the device comprising:
a voltage detection portion that measures the voltage and temperature of the rechargeable battery;
a computing portion that predicts and calculates the remaining power of the rechargeable battery, based on the voltage and the temperature; and
a controller that controls an operation of the battery remaining power predicting device and the computing portion,
wherein the controller executes a battery remaining power predicting flow for predicting and calculating the remaining power of the rechargeable battery, the battery remaining power prediction flow regressively calculating the battery remaining power, based on the measured voltage and temperature and a battery internal impedance in a battery equivalent circuit, and
the controller executes a secular change estimating flow for estimating a secular change in battery characteristics using a case where a battery current is in a constant current state.
2. The battery remaining power predicting device according to claim 1 , wherein the battery equivalent circuit comprises:
a voltage source that outputs a battery open circuit voltage,
a first resistor connected in series with the voltage source, and
an internal impedance including an impedance element connected in series with the first resistor and having a resistor and a capacitor connected in parallel.
3. The battery remaining power predicting device according to claim 2 , wherein the controller executes the secular change estimating flow to:
determine whether the battery characteristics are in a measurable state,
determine that the rechargeable battery is in a charging state,
measure a battery voltage and a battery temperature at a first time, and a battery voltage and a battery temperature after a unit time from the first time,
regressively calculate a battery remaining power at the first time, based on the measured battery voltage and temperature at the first time, the measured battery voltage and temperature after the unit time from the first time, a battery remaining power before the unit time from the first time, and a voltage applied across the impedance element,
estimate secular change coefficients of the battery characteristics using the battery remaining power,
determine whether the estimation of the secular change coefficients is executed a prescribed number of times,
calculate an average value of the secular change coefficients, and
determine a secular change in the battery characteristics from the average value of the secular change coefficients and updates an estimated value of the secular change in the battery characteristics.
4. The battery remaining power predicting device according to claim 2 , comprising a constant current source as a battery load,
wherein when the controller determines that an operating current of a system operated by the rechargeable battery is in a state of not greater than a prescribed current, the control portion activates the constant current source to bring the battery current to a constant current state, and thereafter measures the battery voltage and the battery temperature and estimates the secular change in the battery characteristics.
5. The battery remaining power predicting device according to claim 4 , wherein the controller executes the secular change estimating flow to:
determine whether the battery characteristics are in a measurable state,
set the constant current source as a battery load when the battery characteristics are in the measurable state,
and the calculating portion measures the elapse of a prescribed time,
after the prescribed time elapses, measure a battery voltage and a battery temperature at a first time, and a battery voltage and a battery temperature after a unit time from the first time,
regressively calculate a battery remaining power at the first time, based on the measured battery voltage and temperature at the first time, the measured battery voltage and temperature after the unit time from the first time, a battery remaining power before the unit time from the first time, and a voltage applied across the impedance element,
estimate secular change coefficients of the battery characteristics using the battery remaining power,
determine whether the estimation of the secular change coefficients is executed a prescribed number of times,
disconnect the constant current source from the rechargeable battery when the estimation is executed the prescribed number of times,
calculate an average value of the secular change coefficients, and
calculate a secular change in the battery characteristics from the average value of the secular change coefficients and update an estimated value of the secular change in the battery characteristics.
6. The battery remaining power predicting device according to claim 1 , wherein the internal impedance of the battery equivalent circuit comprises a plurality of the impedance elements connected in series.
7. The battery remaining power predicting device according to claim 6 , wherein the control portion executes the secular change estimating flow to:
determine whether the battery characteristics are in a measurable state,
determine that the rechargeable battery is in a charging state,
measure a battery voltage and a battery temperature at a first time, and a battery voltage and a battery temperature after a unit time from the first time,
regressively calculate a battery remaining power at the first time, based on the measured battery voltage and temperature at the first time, the measured battery voltage and temperature after the unit time from the first time, and a battery remaining power before the unit time from the first time,
estimate secular change coefficients of the battery characteristics using the battery remaining power,
determine whether the estimation of the secular change coefficients is executed a prescribed number of times,
calculate an average value of the secular change coefficients, and
calculate a secular change in the battery characteristics from the average value of the secular change coefficients and updates an estimated value of the secular change in the battery characteristics.
8. The battery remaining power predicting device according to claim 6 , comprising a constant current source as a battery load,
wherein when the controller determines that an operating current of a system operated by the rechargeable battery is in a state of not greater than a prescribed current, the controller activates the constant current source to bring the battery current to a constant current state, and thereafter measures the battery voltage and the battery temperature and estimates the secular change in the battery characteristics.
9. The battery remaining power predicting device according to claim 8 , wherein the controller executes the secular change estimating flow to:
determine whether the battery characteristics are in a measurable state,
set the constant current source as a battery load when the battery characteristics are in the measurable state,
measure the elapse of a prescribed time,
after the prescribed time elapses, measure a battery voltage and a battery temperature at a first time, and a battery voltage and a battery temperature after a unit time from the first time,
regressively calculate a battery remaining power at the first time, based on the measured battery voltage and temperature at the first time, the measured battery voltage and temperature after the unit time from the first time, and a battery remaining power before the unit time from the first time,
estimate secular change coefficients of the battery characteristics using the battery remaining power,
determine whether the estimation of the secular change coefficients is executed a prescribed number of times,
disconnect the constant current source from the rechargeable battery when the estimation is executed the prescribed number of times,
calculate an average value of the secular change coefficients, and
calculate a secular change in the battery characteristics from the average value of the secular change coefficients and update an estimated value of the secular change in the battery characteristics.
10. The battery remaining power predicting device according to claim 1 , wherein a time interval at which a battery remaining power prediction computation is performed is assumed to be 2N (where N: integer) seconds.
11. A battery pack comprising:
a rechargeable battery and a MOSFET for load current control connected in series between first and second external terminals to which a load is connected;
a control circuit which is connected across the rechargeable battery and which monitors a state of the rechargeable battery and controls the MOSFET; and
the battery remaining power predicting device according to claim 1 , which is connected across the rechargeable battery and predicts a remaining power of the rechargeable battery.