Method and apparatus for estimating battery state of health
Estimating a battery state of health (SOH) is described. The state of heath is estimated by obtaining a partial charge or discharge capacity of a target battery in a state of charge (SOC) interval of each of a plurality of SOCs. First dV/dSOC data is separately calculated for each SOC in an m th preset battery capacity based on the m th preset battery capacity and the partial charge or discharge capacity in the SOC interval of each SOC. A smallest overall dV/dSOC data deviation is determined from all overall dV/dSOC data deviations corresponding to M preset battery capacities. A preset battery capacity is determined corresponding to the smallest overall dV/dSOC data deviation as a retention capacity of an aged target battery. The retention capacity of the aged target battery is divided by a retention capacity of the target battery in a new battery state, to obtain the SOH estimate of the target battery.
1. A method for estimating a battery state of health (SOH), wherein the method comprises:
obtaining N states of charge (SOCs) of a target battery in N states, where each one of the N SOCs is a ratio of a remaining capacity of the target battery to a full charge capacity of the target battery;
calculating first dV/dSOC data of each SOC in an n th SOC based on a charge/discharge capacity of the target battery in the n th SOC and an m th preset capacity of the battery, wherein N represents a quantity of SOCs, N is a positive integer not less than 2, n is a positive integer less than or equal to N, m is a positive integer from 1 to M, and M is a quantity of preset capacities;
separately calculating, based on a dV/dSOC-SOC characteristic function, second dV/dSOC data corresponding to each SOC, wherein the dV/dSOC-SOC characteristic function is obtained by charging or discharging the target battery based on a preset current in a new battery state, the preset current is not greater than 1/20 Q BOL , and Q BOL indicates a retention capacity of the target battery in the new battery state;
obtaining an m th overall dV/dSOC data deviation of the plurality of SOCs through calculation based on the first dV/dSOC data of each SOC in the m th preset battery capacity and the second dV/dSOC data corresponding to each SOC;
determining a smallest overall dV/dSOC data deviation from M overall dV/dSOC data deviations;
determining a preset battery capacity corresponding to the smallest overall dV/dSOC data deviation as a retention capacity of an aged target battery; and
obtaining an SOH of the target battery through calculation based on the retention capacity of the aged target battery.
2. The method according to claim 1 , wherein the method further comprises:
obtaining a partial charge or discharge capacity of the target battery in a SOC interval of each SOC in the n th SOC, wherein the SOC interval of each SOC is an interval whose start SOC is the SOC and whose length is dSOC, and the charge/discharge capacity in the n th SOC is a partial charge or discharge capacity in the interval.
3. The method according to claim 2 , wherein the obtaining a partial charge or discharge capacity of the target battery in a SOC interval of each SOC in the n th SOC comprises:
obtaining the partial charge or discharge capacity of the target battery in the SOC interval of each of the plurality of SOCs with reference to the following first preset formula, wherein the first preset formula comprises:
q SOC n =η∫ SOC n -t start SOC n -t end i ( t ) SOC n dt,
wherein SOC n represents the n th SOC, q SOC n represents a partial charge or discharge capacity in a SOC interval of SOC n , η is coulombic efficiency of the target battery, 0<η≤1, SOC n −t start represents a start moment of the SOC interval of SOC n , SOC n −t end represents an end moment of the SOC interval of SOC n , and i(t) SOC n represents a random current in the SOC interval of SOC n .
4. The method according to claim 1 , wherein the obtaining an SOH of the target battery through calculation based on the retention capacity of the aged target battery comprises: dividing the retention capacity of the aged target battery by the retention capacity of the target battery in the new battery state, to obtain the SOH of the target battery.
5. The method according to claim 1 , wherein the separately calculating first dV/dSOC data of each SOC in an n th SOC based on a charge/discharge capacity of the target battery in the n th SOC and an m th preset capacity of the battery comprises:
separately calculating the first dV/dSOC data of each SOC in the m th preset battery capacity based on the m th preset battery capacity and the partial charge or discharge capacity in the SOC interval of each SOC and with reference to a second preset formula, wherein the second preset formula comprises:
g
1
(
SOC
n
)
=
Q
m
(
dV
dq
)
SOC
n
,
wherein Q m represents the m th preset battery capacity, SOC n represents the n th SOC, g 1 (SOC n ) represents first dV/dSOC data of SOC n in the m th preset battery capacity, V represents a voltage, q represents a partial charge or discharge capacity, and
(
dV
dq
)
SOC
n
represents
dV
dq
corresponding to SOC n .
6. The method according to claim 5 , wherein when the target battery works in a discharge state, the second preset formula specifically comprises:
g
1
(
SOC
n
)
=
Q
m
(
dV
dq
)
SOC
n
=
Q
m
OCV
SOC
n
-
t
end
-
OCV
SOC
n
-
t
start
q
SOC
n
′
,
wherein SOC n −t start represents the start moment of the SOC interval of SOC n , SOC n −t end represents the end moment of the SOC interval of SOC n , OCV SOC n -t start represents an open circuit voltage (OCV) at SOC n −t start , OCV SOC n -t end represents an OCV at SOC n −t end , and q′ SOC n represents a partial discharge capacity in the SOC interval of SOC n .
7. The method according to claim 1 , wherein the dV/dSOC-SOC characteristic function comprises:
g
0
(
SOC
n
)
=
a
0
+
∑
j
=
1
6
(
a
j
*
sin
(
j
*
ω
*
SOC
n
)
+
b
j
*
cos
(
j
*
ω
*
SOC
n
)
)
,
wherein SOC n represents the n th SOC, SOC n is an independent variable of the dV/dSOC-SOC characteristic function, g 0 (SOC n ) represents second dV/dSOC data corresponding to SOC n , j represents an order, a 0 , a j , and b j are coefficients of terms, sin( ) represents a sine function, cos( ) represents a cosine function, and ω represents frequency.
8. The method according to claim 1 , wherein the calculating an m th overall dV/dSOC data deviation of the plurality of SOCs based on the first dV/dSOC data of each SOC in the m th preset battery capacity and the second dV/dSOC data corresponding to each SOC comprises:
calculating the m th overall dV/dSOC data deviation of the plurality of SOCs based on the first dV/dSOC data of each SOC in the m th preset battery capacity and the second dV/dSOC data corresponding to each SOC and with reference to a third preset formula, wherein the third preset formula comprises:
G
m
=
∑
n
=
1
N
(
g
0
(
SOC
n
)
-
g
1
(
SOC
n
)
)
2
,
wherein N represents the quantity of SOCs, N is a positive integer not less than 2, SOC n represents the n th SOC, g 0 (SOC n ) represents the second dV/dSOC data corresponding to SOC n , g 1 (SOC n ) represents the first dV/dSOC data of SOC n in the m th preset battery capacity, and G m represents the m th overall dV/dSOC data deviation of the plurality of SOCs.
9. An apparatus for estimating a battery state of health SOH, wherein the apparatus comprises an obtaining module and a calculation module, wherein
the obtaining module is configured to obtain N states of charge SOCs of a target battery in N states, wherein the SOC is a ratio of a remaining capacity of the target battery to a full charge capacity of the target battery; and
the calculation module is configured to:
separately calculate first dV/dSOC data of each SOC in an n th SOC based on a charge/discharge capacity of the target battery in the n th SOC and an m th preset capacity of the battery, wherein N represents a quantity of SOCs, N is a positive integer not less than 2, n is a positive integer less than or equal to N, m is a positive integer from 1 to M, and M is a quantity of preset capacities;
separately calculate, based on a dV/dSOC-SOC characteristic function, second dV/dSOC data corresponding to each SOC, wherein the dV/dSOC-SOC characteristic function is obtained by charging or discharging the target battery based on a preset current in an new battery state, the preset current is not greater than 1/20 Q BOL , and Q BOL indicates a retention capacity of the target battery in the new battery state;
obtain an m th overall dV/dSOC data deviation of the plurality of SOCs through calculation based on the first dV/dSOC data of each SOC in the m th preset battery capacity and the second dV/dSOC data corresponding to each SOC;
determine a smallest overall dV/dSOC data deviation from M overall dV/dSOC data deviations;
determine a preset battery capacity corresponding to the smallest overall dV/dSOC data deviation as a retention capacity of an aged target battery; and
obtain an SOH of the target battery through calculation based on the retention capacity of the aged target battery.
10. The apparatus according to claim 9 , wherein the obtaining module is further configured to obtain a partial charge or discharge capacity of the target battery in a SOC interval of each SOC in the n th SOC, wherein the SOC interval of each SOC is an interval whose start SOC is the SOC and whose length is dSOC, and the charge/discharge capacity in the n th SOC is a partial charge or discharge capacity in the interval.
11. The apparatus according to claim 10 , wherein the obtaining module is specifically configured to:
obtain the partial charge or discharge capacity of the target battery in the SOC interval of each of the plurality of SOCs with reference to the following first preset formula, wherein the first preset formula comprises:
q SOC n =η∫ SOC n -t start SOC n -t end i ( t ) SOC n dt,
wherein SOC n represents the n th SOC, q SOC n represents a partial charge or discharge capacity in a SOC interval of SOC n , η is coulombic efficiency of the target battery, 0<η≤1, SOC n −t start represents a start moment of the SOC interval of SOC n , SOC n −t end represents an end moment of the SOC interval of SOC n , and i(t) SOC n represents a random current in the SOC interval of SOC n .
12. The apparatus according to claim 9 , wherein the calculation module is specifically configured to divide the retention capacity of the aged target battery by the retention capacity of the target battery in the new battery state, to obtain the SOH of the target battery.
13. The apparatus according to claim 9 , wherein the calculation module is specifically configured to:
separately calculate the first dV/dSOC data of each SOC in the m th preset battery capacity based on the m th preset battery capacity and the partial charge or discharge capacity in the SOC interval of each SOC and with reference to a second preset formula, wherein the second preset formula comprises:
g
1
(
SOC
n
)
=
Q
m
(
dV
dq
)
SOC
n
,
wherein Q m represents the m th preset battery capacity, SOC n represents the n th SOC, g 1 (SOC n ) represents first dV/dSOC data of SOC n in the m th preset battery capacity, V represents a voltage, q represents a partial charge or discharge capacity, and
(
dV
dq
)
SOC
n
represents
dV
dq
corresponding to SOC n .
14. The apparatus according to claim 13 , wherein when the target battery works in a discharge state, the second preset formula specifically comprises:
g
1
(
SOC
n
)
=
Q
m
(
dV
dq
)
SOC
n
=
Q
m
OCV
SOC
n
-
t
end
-
OCV
SOC
n
-
t
start
q
SOC
n
′
,
wherein SOC n −t start represents the start moment of the SOC interval of SOC n , SOC n −t end represents the end moment of the SOC interval of SOC n , OCV SOC n -t end represents an open circuit voltage (OCV) at SOC n −t start , OCV SOC n -t start represents an OCV at SOC n −t end , and q′ SOC n represents a partial discharge capacity in the SOC interval of SOC n .
15. The apparatus according to claim 9 , wherein the dV/dSOC-SOC characteristic function comprises:
g
0
(
SOC
n
)
=
a
0
+
∑
j
=
1
6
(
a
j
*
sin
(
j
*
ω
*
SOC
n
)
+
b
j
*
cos
(
j
*
ω
*
SOC
n
)
)
,
wherein SOC n represents the n th SOC, SOC n is an independent variable of the dV/dSOC-SOC characteristic function, g 0 (SOC n ) represents second dV/dSOC data corresponding to SOC n , j represents an order, a 0 , a j , and b j are coefficients of terms, sin( ) represents a sine function, cos( ) represents a cosine function, and w represents frequency.
16. The apparatus according to claim 9 , wherein the calculation module is specifically configured to:
calculate the m th overall dV/dSOC data deviation of the plurality of SOCs based on the first dV/dSOC data of each SOC in the m th preset battery capacity and the second dV/dSOC data corresponding to each SOC and with reference to a third preset formula, wherein the third preset formula comprises:
G
m
=
∑
n
=
1
N
(
g
0
(
SOC
n
)
-
g
1
(
SOC
n
)
)
2
,
wherein N represents the quantity of SOCs, N is a positive integer not less than 2, SOC n represents the n th SOC, g 0 (SOC n ) represents the second dV/dSOC data corresponding to SOC n , g 1 (SOC n ) represents the first dV/dSOC data of SOC n in the m th preset battery capacity, and G m represents the m th overall dV/dSOC data deviation of the plurality of SOCs.