Maintenance method of power battery pack

1. An improved maintenance method of a power battery pack, wherein the battery pack comprises several single cells connected in series, comprising the following steps:

(1) conducting analysis on battery pack Bat={Bat 1 , Bat 2 . . . Bat n }, n is the number of battery pack single cells, n≥3, and n is an integer;

(2) data preprocessing; measuring and selecting m continuous voltages “vol”, currents “curr”, and temperatures temp collected, m is an integer equal to or greater than 3, to get the raw data matrix Z;

Z

=

[

vol

11

…

vol

1

⁢

m

…

…

…

vol

n

⁢

⁢

1

…

vol

nm

cur

1

…

cur

m

temp

1

…

temp

m

]

the peak values of voltage, current and temperature data are removed and the averages are calculated to get the required voltage, current and temperature data, volavg i , curavg, tempavg, 1≤i≤n;

volavg

i

=

1

n

-

2

⁢

(

∑

j

=

1

m

⁢

⁢

vol

ij

-

min

1

≤

j

≤

m

⁢

{

vol

ij

}

-

max

1

≤

j

≤

m

⁢

{

vol

ij

}

)

curavg

=

1

n

-

2

⁢

(

∑

j

=

1

m

⁢

⁢

cur

j

-

min

1

≤

j

≤

m

⁢

{

cur

j

}

-

max

1

≤

j

≤

m

⁢

{

cur

j

}

)

tempavg

=

1

n

-

2

⁢

(

∑

j

=

1

m

⁢

⁢

temp

j

-

min

1

≤

j

≤

m

⁢

{

temp

j

}

-

max

1

≤

j

≤

m

⁢

{

temp

j

}

)

(3) conducting normalization processing of voltage data “volavg i ” obtained in (2) and state of charge SOC i , state of health SOH i of single cell, as follows:

volavg

i

_

=

volavg

i

-

min

1

≤

i

≤

n

⁢

{

volavg

i

}

max

1

≤

i

≤

n

⁢

{

volavg

i

}

-

min

1

≤

i

≤

n

⁢

{

volavg

i

}

SOCSOH

i

_

=

SOC

i

×

SOH

i

-

min

1

≤

i

≤

n

⁢

{

SOC

i

×

SOH

i

}

max

1

≤

i

≤

n

⁢

{

SOC

i

×

SOH

i

}

-

min

1

≤

i

≤

n

⁢

{

SOC

i

×

SOH

i

}

⁢

volavg

i

_

is the voltage of the ith single cell after normalization, SOCSOH i is the product of SOC, SOH of the ith single cell after normalization, 1≤i≤n, i is an integer;

(4) calculating the charging and discharging levels of single cell that needs to maintain, and determining the battery sets that require charging and discharging maintenance;

the charging maintenance level of each cell is calculated as follows:

dCha

i

=

w

1

×

10

×

(

1

n

⁢

∑

j

=

1

n

⁢

⁢

volavg

j

_

-

volavg

i

_

)

+

w

2

⁡

(

1

n

⁢

∑

j

=

1

n

⁢

⁢

SOCSOH

j

_

-

SOCSOH

i

_

)

dDis

i

=

w

1

×

10

×

(

⁢

volavg

i

_

-

1

n

⁢

∑

j

=

1

n

⁢

volavg

j

_

)

+

w

2

(

⁢

SOCSOH

i

_

-

1

n

⁢

∑

j

=

1

n

⁢

SOCSOH

j

_

)

where w 1 , w 2 are the weighted values of voltage factor and remaining capacity factor respectively, and w 1 +w 2 =1;

for all single cells, when dCha i >d cha , it is considered that the i-th single cell needs charging maintenance, d cho is the established charge maintenance threshold; when dDis i >d dis , it is considered that the i-th single cell needs discharging maintenance, and d dis is the established discharge maintenance threshold;

thus, the battery set that needs charging maintenance is Bat1={Bat1 1 , Bat1 2 . . . Bat1 x }, and the battery set that needs discharging maintenance is Bat2={Bat2 1 , Bat2 2 . . . Bat2 y }, and x<n, y<n;

(5) the charging maintenance current is a constant value Cur cho , the discharging maintenance current is a constant value Cur dis , to maintain balance, the ratio of number of batteries that need charging maintenance to the number of batteries that need discharging maintenance is

Cur

dis

Cur

cha

,

then the ratio value is processed, to get the corresponding fraction in lowest term, which is

Cur

dis

′

Cur

cha

′

;

when Cur dis ′≥Cur cho ′, and Cur dis ′>d, d is the maximum number of charging maintenance and n/4≤d≤n/2, then

h

cha

h

dis

=

d

⌈

d

×

Cur

cha

′

Cur

dis

′

⌉

,

that is the ratio of d to

d

×

Cur

cha

′

Cur

dis

′

rounded up to an integer; when Cur dis ′≥Cur cho ′, and Cur dis ′≤d, then

h

cha

h

dis

=

Cur

dis

′

Cur

cha

′

;

when

⁢

⁢

Cur

dis

′

<

Cur

cha

′

⁢

,

⁢

and

⁢

Cur

cha

′

>

d

,

then

⁢

⁢

h

cha

h

dis

=

⌊

Cur

dis

′

d

×

Cur

cha

′

⌋

d

,

that is the ratio of

Cur

dis

′

d

×

Cur

cha

′

to d rounded down to an integer; when Cur dis ′<Cur cho ′, and Cur cho ′≤d, then

h

cha

h

dis

=

Cur

dis

′

Cur

cha

′

;

h cho is the numerator of optimal ratio of the number of batteries that need charging maintenance to the number of batteries that need discharging maintenance under the maximum number of charging maintenance d, which is an integer; h dis is the denominator of optimal ratio of the number of batteries that need charging maintenance to the number of batteries that need discharging maintenance under the maximum number of charging maintenance d, which is an integer;

when

x

y

>

h

cha

h

dis

,

the number of batteries that need discharging maintenance is

Num

dis

=

⌊

y

h

dis

⌋

×

h

dis

,

the product of

y

h

dis

rounded down to an integer and h dis , the number of batteries that need charging maintenance is

Num

cha

=

⌊

y

h

dis

⌋

×

h

cha

,

the product of

y

h

dis

rounded down to an integer and h cho ; when

x

y

<

h

cha

h

dis

,

the number of batteries that need discharging maintenance is

Num

dis

=

⌊

x

h

cha

⌋

×

h

dis

,

the product of

x

h

cha

rounded down to an integer and, the number of batteries that need charging maintenance is

Num

cha

=

⌊

x

h

cha

⌋

×

h

cha

,

the product of

x

h

cha

rounded down to an integer and h cha ; when

x

y

=

h

cha

h

dis

,

the number of batteries that need charging maintenance is Num cha =x, the number of batteries that need discharging maintenance is Num dis =y;

(6) sequencing the battery sets Bat1 and Bat2 in a descending order according to the degrees of charging maintenance and discharging maintenance of all batteries, to get the ordered set Bat3={Bat3 1 , Bat3 2 . . . Bat3 x } that need charging maintenance, and Bat3 1 ≥Bat3 2 ≥ . . . ≥Bat3 x , to get the ordered set Bat4={Bat4 1 , Bat4 2 , . . . Bat4 y } that need discharging maintenance, and Bat4 1 ≥Bat4 2 ≥ . . . ≥Bat4 y ;

(7) selecting from Bat3, Bat4 obtained from (6) according to the number of batteries that need charging maintenance and discharging maintenance, to further obtain the sets of batteries that need charging maintenance and discharging maintenance, the set of batteries that needs charging maintenance is BatCha={Bat3 1 , Bat3 2 . . . Bat3 Num cha }, and the set of batteries that needs discharging maintenance is BatDis={Bat4 1 , Bat4 2 . . . Bat4 Num dis };

(8) the battery maintenance system performing the charging maintenance of single cells in battery set BatCha, and performing the discharging maintenance of single cells in battery set BatDis.

2. The improved maintenance method of power battery pack according to claim 1 , wherein the charge maintenance threshold is d cha =0.2 in the step (4).

3. The improved maintenance method of power battery pack according to claim 1 , wherein the discharge maintenance threshold is d dis =0.2 in the step (4).

4. The improved maintenance method of power battery pack according to claim 1 , wherein d is an integer closest to (n/3) in the step (5).