Method for determining the capacity of an electrical energy storage unit
A method for determining the capacity of an electrical energy storage unit with-in an electrical energy storage system. The system includes a plurality of electrical energy storage units and at least one switching means. The capacity of the electrical energy storage unit is determined from a current flow path of the system in the charging. The electrical energy storage unit is disconnected from the current flow path of the electrical energy storage system and a first voltage value is determined, the electrical energy storage unit is connected into the current flow path and charged and/or discharged, the electrical energy storage unit is disconnected from the current flow path again and a second voltage value is determined, and the capacity of the electrical energy storage unit is determined on based on the first voltage value and the second voltage value.
1. A method for determining the capacity of an electrical energy storage unit ( 2 ) within an electrical energy storage system ( 1 ) that includes a plurality of electrical energy storage units ( 2 ), a sensor, and at least one switch ( 3 ), which is designed to switch the electrical energy storage unit ( 2 ) whose capacity is being determined electrically out of a current flow path ( 5 ) of the electrical energy storage system ( 1 ) and/or to switch said electrical energy storage unit ( 2 ) electrically into the current flow path ( 5 ), wherein the sensor is configured to detect a voltage of the electrical energy storage unit ( 2 ), said method comprising the following steps:
a) switching, by the switch ( 3 ), the electrical energy storage unit ( 2 ) out of the current flow path ( 5 ) of the electrical energy storage system ( 1 );
b) determining, by the sensor, a first voltage value of a terminal voltage of the electrical energy storage unit ( 2 );
c) switching, by the switch ( 3 ), the electrical energy storage unit ( 2 ) into the current flow path ( 5 ) of the electrical energy storage system ( 1 );
d) charging and/or discharging the electrical energy storage unit ( 2 ) with a predefined first quantity of charge and/or up to a predefined first state of charge and/or up to a predefined first voltage level;
e) switching, by the switch ( 3 ), the electrical energy storage unit ( 2 ) out of the current flow path ( 5 ) of the electrical energy storage system ( 1 ) again
f) determining, by the sensor, a second voltage value of the terminal voltage of the electrical energy storage unit ( 2 ); and
g) determining, by an electronic control unit, the capacity of the electrical energy storage unit ( 2 ) in dependence on the first voltage value and the second voltage value.
2. The method as claimed in claim 1 , wherein the determination of the first voltage value in step b) takes place after a predefined first wait time and/or when a predefined first rate of change of the terminal voltage has been reached.
3. The method as claimed in claim 1 , wherein the determination of the second voltage value in step f) takes place after a predefined second wait time and/or when a predefined second rate of change of the terminal voltage has been reached.
4. The method as claimed in claim 1 , wherein steps a) to f) are performed repeatedly, and more than two voltage values of the terminal voltage are determined.
5. The method as claimed in claim 1 , wherein the determination of the capacity in step g) takes place by adaptation of a preset no-load voltage curve in dependence on the determined voltage values.
6. The method as claimed in claim 1 , wherein in each case the state of charge of the electrical energy storage unit ( 2 ) is determined from the determined voltage values.
7. A computer program, which is designed to implement all of the steps in the method as claimed in claim 1 .
8. A machine-readable storage medium on which the computer program as claimed in claim 7 is stored.
9. An apparatus ( 4 ) for determining the capacity of an electrical energy storage unit ( 2 ) within an electrical energy storage system ( 1 ) comprising a plurality of electrical energy storage units ( 2 ) and a sensor, wherein the electrical energy storage system ( 1 ) has at least one switch ( 3 ), which is designed to switch the electrical energy storage unit ( 2 ) whose capacity is being determined electrically out of a current flow path ( 5 ) of the electrical energy storage system ( 1 ) and/or to switch said electrical energy storage unit ( 2 ) electrically into the current flow path ( 5 ), wherein the sensor is configured to detect a voltage of the electrical energy storage unit ( 2 ), comprising electronic control unit configured to
switch, using the switch ( 3 ), the electrical energy storage unit ( 2 ) out of the current flow path ( 5 ) of the electrical energy storage system ( 1 );
determine, using the sensor, a first voltage value of a terminal voltage of the electrical energy storage unit ( 2 );
switch, using the switch ( 3 ), the electrical energy storage unit ( 2 ) into the current flow path ( 5 ) of the electrical energy storage system ( 1 );
control charging and/or discharging of the electrical energy storage unit ( 2 ) with a predefined first quantity of charge and/or up to a predefined first state of charge and/or up to a predefined first voltage level;
switch, using the switch ( 3 ), the electrical energy storage unit ( 2 ) out of the current flow path ( 5 ) of the electrical energy storage system ( 1 ) again;
determine, using the sensor, a second voltage value of the terminal voltage of the electrical energy storage unit ( 2 ); and
determine the capacity of the electrical energy storage unit ( 2 ) in dependence on the first voltage value and the second voltage value.
10. An electrical energy storage system ( 1 ) comprising:
a plurality of electrical energy storage units ( 2 );
a sensor is configured to detect a voltage of each of the plurality of electrical energy storage units;
at least one switch ( 3 ), which is configured to switch at least one electrical energy storage unit ( 2 ) whose capacity is being determined electrically out of a current flow path ( 5 ) of the electrical energy storage system ( 1 ) and/or to switch said at least one electrical energy storage unit ( 2 ) electrically into the current flow path ( 5 ); and electronic control unit configured to
switch, using the switch, the electrical energy storage unit ( 2 ) out of the current flow path ( 5 ) of the electrical energy storage system ( 1 ) by means of the switching means ( 3 );
determine, using the sensor, a first voltage value of a terminal voltage of the electrical energy storage unit ( 2 );
switch, using the switch, the electrical energy storage unit ( 2 ) into the current flow path ( 5 ) of the electrical energy storage system ( 1 );
control charging and/or discharging of the electrical energy storage unit ( 2 ) with a predefined first quantity of charge and/or up to a predefined first state of charge and/or up to a predefined first voltage level;
switch, using the switch, the electrical energy storage unit ( 2 ) out of the current flow path ( 5 ) of the electrical energy storage system ( 1 ) again;
determine, using the sensor, a second voltage value of the terminal voltage of the electrical energy storage unit ( 2 ); and
determine the capacity of the electrical energy storage unit ( 2 ) in dependence on the first voltage value and the second voltage value.
11. The method as claimed in claim 1 , wherein the determination of the first voltage value in step b) takes place after a predefined first wait time and/or when a predefined first rate of change of the terminal voltage has been reached, wherein the determination of the second voltage value in step f) takes place after a predefined second wait time and/or when a predefined second rate of change of the terminal voltage has been reached, wherein the determination of the capacity in step g) takes place by adaptation of a preset no-load voltage curve in dependence on the determined voltage values.
12. The method as claimed in claim 1 , wherein the sensor is connected to the electrical energy storage unit ( 2 ) and the sensor is configured to determine a voltage for the electrical energy storage unit ( 2 ).
13. The method as claimed in claim 1 , wherein the switch ( 3 ) is at least one selected from the group consisting of: a full bridge switch and a half bridge switch.