Battery SOC estimating apparatus and method
A battery state of charge estimating apparatus according to an embodiment of the present disclosure includes a charging and discharging unit for receiving a control signal including a C-rate and for charging and discharging a battery at the C-rate included in the control signal; a measuring unit for measuring a voltage of the battery in a charging and discharging process of the battery; and a control unit for transmitting the control signal to the charging and discharging unit, changing the C-rate included in the control signal whenever the voltage value measured by the measuring unit reaches a preset threshold value, and estimating SOC of the battery based on the result of comparing the changed C-rate with a preset cutoff value.
1 . A battery state of charge (SOC) estimating apparatus, comprising:
a charging and discharging unit configured to:
receive a control signal including a C-rate; and
charge and discharge a battery at the C-rate included in the control signal;
a measuring unit configured to measure a voltage of the battery in a charging and discharging process of the battery; and
a control unit configured to:
transmit the control signal to the charging and discharging unit,
change the C-rate included in the control signal in response to the voltage value measured by the measuring unit reaching a preset threshold voltage value, and
estimate a SOC of the battery based on a result of comparing the changed C-rate with a preset cutoff value.
2 . The battery SOC estimating apparatus according to claim 1 ,
wherein in response to the measured voltage value reaching the preset threshold voltage value, the control unit is configured to decrease the C-rate by a preset C-rate change ratio.
3 . The battery SOC estimating apparatus according to claim 1 ,
wherein in response the changed C-rate being equal to or less than the cutoff value, the control unit is configured to estimate the SOC of the battery as a preset SOC.
4 . The battery SOC estimating apparatus according to claim 3 ,
wherein the control unit is configured to:
in response to the changed C-rate becoming equal to or less than the cutoff value while the battery is being charged, estimate the SOC of the battery as 100%, and
in response to the changed C-rate becoming equal to or less than the cutoff value while the battery is being discharged, estimate the SOC of the battery as 0%.
5 . The battery SOC estimating apparatus according to claim 1 ,
wherein in response to the changed C-rate exceeding the cutoff value, the control unit is configured to:
set a criterion SOC for the battery at an initial change time when the C-rate is initially changed, and
estimate the SOC of the battery based on the criterion SOC, a number of changes of the C-rate after the initial change time and an expected number of changes of the C-rate expected until charging and discharging of the battery is terminated in the charging and discharging process.
6 . The battery SOC estimating apparatus according to claim 5 ,
wherein in response to the changed C-rate exceeding the cutoff value the control unit is configured to estimate SOC of the battery based on Equation 1 below,
B
SOC
=
R
SOC
+
❘
"\[LeftBracketingBar]"
T
SOC
-
R
SOC
❘
"\[RightBracketingBar]"
n
×
m
[
Equation
1
]
where B SOC is an estimated SOC of the battery, T SOC is a SOC value determined in advance according to a charging and discharging state of the battery, R SOC is the criterion SOC, n is the expected number of changes of the C-rate, and m is the number of changes of the C-rate.
7 . The battery SOC estimating apparatus according to claim 5 ,
wherein the control unit is configured to calculate the expected number of changes of the C-rate based on the changed C-rate, the cutoff value and a preset C-rate change ratio.
8 . The battery SOC estimating apparatus according to claim 7 ,
wherein the control unit is configured to calculate the expected number of changes of the C-rate based on Equation 2 below,
n
=
⌊
log
d
x
y
⌋
[
Equation
2
]
where n is the expected number of changes of the C-rate, d is the C-rate change ratio, x is the cutoff value, and y is an initial C-rate value included in the control signal.
9 . The battery SOC estimating apparatus according to claim 5 ,
wherein the measuring unit is configured to further measure a current of the battery in the charging and discharging process, and
wherein the control unit is configured to set the criterion SOC by integrating the current of the battery measured by the measuring unit from a start time of the charging and discharging to the initial change time.
10 . The battery SOC estimating apparatus according to claim 1 ,
wherein in response to the changed C-rate being less than or equal to the cutoff value, the control unit is configured to transmit a charging and discharging termination signal to the charging and discharging unit for terminating charging and discharging of the battery, and
wherein in response to the changed C-rate exceeding the cutoff value, the control unit is configured to transmit the control signal including the changed C-rate to the charging and discharging unit.
11 . A battery pack, comprising the battery SOC estimating apparatus according to claim 1 .
12 . A battery state of charge (SOC) estimating method, comprising:
a charging and discharging step of receiving a control signal including a C-rate and charging and discharging a battery at the C-rate included in the control signal;
a voltage measuring step of measuring a voltage of the battery in a charging and discharging process of the battery;
a C-rate changing step of changing the C-rate included in the control signal in response to the voltage value measured in the voltage measuring step reaching a preset threshold voltage value; and
a SOC estimating step of estimating a SOC of the battery based on a result of comparing the C-rate changed in the C-rate changing step with a preset cutoff value.