Method for equalizing different states of charge of batteries

Patent metadata

Field	Value
Publication number	US-9356452-B2
Application number	US-201414218655-A
Country	US
Kind code	B2
Filing date	Mar 18, 2014
Priority date	Mar 20, 2013
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

A method for reducing a total charge loss of battery cells by equalizing states of charge includes making an initial check as to whether a temperature of at least one balancing unit lies below a preselectable temperature limit. Thereupon a check takes place as to whether a charging process of the battery cells has completed and the state of charge of the battery cells is >90%. A determination then follows as to whether a maximum state of charge difference between battery cells lies above an adjustable limit (DELTA_SoC).

First claim

What is claimed is:

1. A method for reducing a total charge loss of battery cells by equalizing states of charge comprising:
a) checking boundary conditions as to whether (i) a temperature of at least one balancing unit is below a preselectable temperature limit, and (ii) a charging process of the battery cells has completed and the state of charge (SoC) of the battery cells is greater than 90%,
b) determining whether a maximum SoC difference of the battery cells lies above an adjustable limit (DELTA_SoC),
c) if steps a) and b) of the method are affirmative, autonomously cell balancing the battery cells by connecting the battery cells to balancing resistances (R 13 bal) for a time period (t i ) with

t
i

=

Q_i
·
R_bal

U_OCV
·

(
SoC_i
)

,

wherein
Q_i charge of a battery cell i of the battery cells to be removed,
U 13 OCV open circuit battery cell voltage,
SoC_i state of charge of the battery cell i, and
R_bal resistance value of the balancing resistance; and

d) switching off the at least one balancing unit after expiry of the time period (t i ).

2. The method according to claim 1 , wherein the charge Q_i of the battery cell i to be removed according to step c) is determined according to the following relationship:
Q _i C _NOM·(SoC 13 i -SoC_MIN) with

C 13 NOM nominal capacitance of the battery cell i.

3. The method according to claim 1 , wherein according to step b) a need for balancing is affirmed if for at least one battery cell of the battery cells the individual state of charge SoC_i of the at least one battery cell is fulfilled by more than the DELTA_SoC being greater than a parameter SoC_MIN.

4. The method according to claim 1 , wherein the at least one balancing unit automatically switches off in the event of heating above a temperature threshold and remains switched off.

5. The method according to claim 1 , wherein the at least one balancing unit remains connected for the time period (t i ), but for no longer than an adjustable maximum time.

6. The method according to claim 3 , wherein:
the parameter SoC_MIN is a minimum SoC of an individual battery cell of the battery cells, and
the parameter SoC_MIN lies above a desired reserve charge.

7. The method according to claim 1 , wherein the DELTA_SoC defines a permissible SoC variance, below which no balancing steps are carried out.

8. The method according to claim 1 , wherein during the balancing, balancing is performed to the DELTA_SoC and a difference between a maximum state of charge and a minimum state of charge of the battery cells corresponds to the DELTA_SoC.

9. The method according to claim 1 , wherein a maximum number of cycles of the at least one balancing unit and coverage of a possible need for symmetrizing by the time period (t i ) of a balancing step are adapted to each other.

10. The method according to claim 1 , wherein specific battery cells or subsets of the battery cells are balanced individually.

Assignees

• Bosch Gmbh Robert
• Samsung Sdi Co Ltd

Inventors

• Steck Armin
• Korn Christian
• Heizmann Marianne
• Gleiter Andreas

Classifications

• H02J7/54 Primary

  Passive balancing, e.g. using resistors or parallel MOSFETs · CPC title

• H02J7/0016 Primary

  Electricity · mapped topic

• H01M10/441

  for several batteries or cells simultaneously or sequentially · CPC title

• H01M10/44 Primary

  Methods for charging or discharging (circuits for charging H02J7/00) · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title