Battery monitoring device, integrated circuit, and battery monitoring system
A battery monitoring device includes a first reference resistor disposed in a path different from a path of current flowing from a battery to a load; a transistor for passing current from the battery to the first reference resistor; and an integrated circuit. The integrated circuit includes: a current measurement unit that measures a first current flowing through the first reference resistor; a voltage measurement unit that measures a first voltage of the battery; and a first calculation unit that calculates an AC impedance of the battery based on the first current measured and the first voltage measured.
1. A battery monitoring device, comprising:
a resistor disposed in a path different from a path of current flowing from a battery to a load;
a transistor for passing current from the battery to the resistor; and
an integrated circuit, wherein:
the integrated circuit includes:
a current measurement unit that measures a first current flowing through the resistor;
a voltage measurement unit that measures a first voltage of the battery;
a first calculation unit that calculates an AC impedance of the battery based on the first current measured and the first voltage measured; and
a signal application unit that applies a control signal to a control terminal of the transistor, and
the signal application unit applies the control signal having a plurality of frequency components to the control terminal.
2. The battery monitoring device according to claim 1 , wherein
the signal application unit is capable of changing a frequency and a voltage value of the control signal.
3. The battery monitoring device according to claim 1 , wherein
the control signal has a burst waveform.
4. The battery monitoring device according to claim 1 , wherein
the integrated circuit further includes a second calculation unit that calculates at least one of a state of charge (SOC) or a state of health (SOH) of the battery using the AC impedance calculated.
5. The battery monitoring device according to claim 1 , wherein
the first calculation unit further includes a Kalman filter unit that calculates a low frequency impedance using at least one of a charging current during charging of the battery or a discharging current during discharging of the battery.
6. The battery monitoring device according to claim 1 , wherein
the integrated circuit further includes a second temperature measurement unit that measures a temperature of the resistor, and
the first calculation unit calculates the AC impedance by further using the temperature of the resistor that was measured.
7. The battery monitoring device according to claim 1 , wherein
the integrated circuit further includes a temperature control unit that controls a temperature of the resistor to be constant.
8. The battery monitoring device according to claim 1 , wherein
the first calculation unit calculates the AC impedance during charging of the battery.
9. The battery monitoring device according to claim 1 , wherein
the first calculation unit calculates the AC impedance during discharging of the battery.
10. The battery monitoring device according to claim 1 , wherein
the first calculation unit calculates the AC impedance during a stoppage of charging and discharging of the battery.
11. The battery monitoring device according to claim 1 , wherein
the battery is one of a plurality of batteries included in a battery pack.
12. A battery monitoring system, comprising:
a plurality of battery monitoring devices each of which is the battery monitoring device according to claim 1 ; and
an integrated control unit that obtains the AC impedance from each of the plurality of battery monitoring devices.
13. A battery monitoring system, comprising:
the battery monitoring device according to claim 1 ; and
a server device disposed at a location away from the battery monitoring device, wherein the server device obtains the AC impedance from the battery monitoring device.
14. A battery monitoring device, comprising:
a resistor disposed in a path different from a path of current flowing from a battery to a load;
a transistor for passing current from the battery to the resistor; and
an integrated circuit,
wherein the integrated circuit includes:
a current measurement unit that measures a first current flowing through the resistor;
a voltage measurement unit that measures a first voltage of the battery;
a first calculation unit that calculates an AC impedance of the battery based on the first current measured and the first voltage measured;
a signal generation unit that generates a first signal which is a sine wave; and
a phase shift unit that shifts a phase of the first signal by 90 degrees to generate a second signal.
15. The battery monitoring device according to claim 14 , wherein the first calculation unit:
converts the first current into a second current which is a complex current, by multiplying the first current measured by each of the first signal and the second signal generated; and
calculates the AC impedance based on the second current.
16. The battery monitoring device according to claim 14 , wherein the first calculation unit:
converts the first voltage into a second voltage which is a complex voltage, by multiplying the first voltage measured by each of the first signal and the second signal generated; and
calculates the AC impedance based on the second voltage.
17. An integrated circuit, comprising:
a signal application unit that applies a control signal to a control terminal of a transistor for passing a current from a battery to a resistor disposed in a path different from a path of current flowing from the battery to a load;
a current measurement unit that measures a first current flowing through the resistor;
a voltage measurement unit that measures a first voltage of the battery; and
a first calculation unit that calculates an AC impedance of the battery based on the first current measured and the first voltage measured; and
the signal application unit applies the control signal having a plurality of frequency components to the control terminal.
18. The integrated circuit according to claim 17 , wherein
the battery is one of a plurality of batteries included in a battery pack, and
the voltage measurement unit includes a plurality of analog-to-digital (AD) converters each for measuring the voltage of a different one of the plurality of batteries,
the integrated circuit further comprising:
a reference bias generation unit that supplies a common reference voltage to the plurality of AD converters.
19. The integrated circuit according to claim 17 , wherein
the battery is one of a plurality of batteries included in a battery pack, and
the voltage measurement unit includes a plurality of analog-to-digital (AD) converters each for measuring the voltage of a different one of the plurality of batteries,
the integrated circuit further comprising:
a timing signal generation unit that supplies each of the plurality of AD converters with a timing signal for synchronizing measurement timings of the plurality of AD converters.