Battery system and associated method for determining the internal resistance of battery cells or battery modules of said battery system

• US 9,634,361 B2
• Filed: 05/24/2013
• Issued: 04/25/2017
• Est. Priority Date: 06/08/2012
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH, Samsung SDI Company Limited
• Original Assignee: Robert Bosch GmbH, Samsung SDI Company Limited
• Inventors: Fink, Holger
• Primary Examiner(s): DIAO, M BAYE
• Application Number:
  US14/405,840
• Publication Number:
  US 20150303532A1
• Time in Patent Office: 1,432 Days
• Field of Search: 324429, 324430
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 3/12 Recording operating variables ; Monitoring of operating variables
• CPC Class Codes: B60L 58/16 responding to battery ageing, e.g. to the number of charging cycles or the state of health [SoH]
• CPC Class Codes: G01K 13/00 Thermometers specially adapted for specific purposes
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 2010/4271 Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
• CPC Class Codes: H01M 2220/20 Batteries in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 50/569 Constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals battery terminal connectors with integrated measuring arrangements G01R31/364
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A method for determining the internal resistance of battery cells of battery modules of a battery includes measuring a first voltage of at least one battery cell of a first battery module at a first time. The first battery module is decoupled from the battery module string in response to a control signal. The first battery module is connected to the battery module string after the first voltage measurement to enable a change in the first voltage of the at least one battery cell in response to a current flowing through the first battery module. A second voltage is measured at a second time where the first battery module is connected to the battery module string for a predefined time interval. The internal resistance is determined with reference to a difference between the first and the second voltage and the current flowing through the first battery module.

Claims

1. A method for determining an internal resistance of battery cells of battery modules of a battery, comprising:

measuring a first voltage of at least one battery cell of a first battery module of the battery modules at a first time, wherein the first battery module is decoupled from a battery module string in response to a first control signal;

connecting, in response to a second control signal, the first battery module to the battery module string after the first voltage measurement to enable a change in the first voltage of the at least one battery cell in response to a current flowing through the first battery module;

measuring a second voltage of the at least one battery cell at a second time after the connection of the first battery module to the battery module string, wherein the first battery module is connected to the battery module string for a predefined time interval; and

determining the internal resistance after the measurement of the second voltage of the at least one battery cell with reference to (i) a difference between the first voltage and the second voltage and (ii) a current value of a current flowing through the first battery module.

2. The method as claimed in claim 1, further comprising:

measuring a value of the current flowing through the battery module at the second time.

3. The method as claimed in claim 1, further comprising:

determining the internal resistance of the at least one battery cell during a charging process of the battery or a discharging process of the battery.

4. The method as claimed in claim 1, further comprising:

determining a level of a change in the current flowing through the first battery module during the predefined time interval;

determining if the level of change exceeds a predefined limit value; and

performing at least one of discarding the measured first battery voltage and the second battery voltage and measuring the first battery voltage and the second battery voltage if the level of change exceeds the predefined limit value.

5. The method as claimed in claim 1, further comprising:

determining a change in an open circuit voltage of the at least one battery cell occurring during the predefined time interval; and

modifying the difference between the first voltage and the second voltage with reference to the determined change in the open circuit voltage.

6. The method as claimed in claim 1, further comprising:

determining the internal resistance under varying boundary conditions, the boundary conditions including at least one of state of charge, temperature, level of the charging or discharging current, and a respectively differently selected time interval between the first voltage measurement and the second voltage measurement; and

storing the internal resistance determined during the varying boundary conditions in a form of an internal resistance characteristic.

7. The method as claimed in claim 1, further comprising:

measuring one or more voltages of the at least one battery cell after measuring the second voltage and before the battery module is decoupled from the battery module string; and

determining a plurality of internal resistances associated with different measurement time intervals and the corresponding measured one or more voltages.

8. A battery system, comprising:

a battery including a battery module string having a plurality of series-connected battery modules, each of the battery modules having at least one battery cell, and an actuable coupling unit, each of the battery modules are configured to be selectively connected to and decoupled from the battery module string with the coupling units to generate a settable output voltage of the battery;

at least one monitoring unit configured to monitor the battery modules and measure at least one of cell voltages and battery module voltages;

at least one current measuring unit interconnected with the battery module string; and

a control and readout unit connected to (i) the coupling units, (ii) the at least one monitoring unit, and (iii) the at least one current measuring unit, the control and readout unit is configured to;

measure a first voltage of the at least one battery cell of a first battery module of the battery modules at a first time, wherein the first battery module is decoupled from a battery module string in response to a first control signal;

connect, in response to a second control signal, the first battery module to the battery module string after the first voltage measurement to enable a change in the first voltage of the at least one battery cell in response to a current flowing through the first battery module;

measure a second voltage of the at least one battery cell at a second time after the connection of the first battery module to the battery module string, wherein the first battery module is connected to the battery module string for a predefined time interval; and

determine the internal resistance after the measurement of the second voltage of the at least one battery cell with reference to (i) a difference between the first voltage and the second voltage and (ii) a current value of a current flowing through the first battery module.

9. The battery system as claimed in claim 8, wherein the battery further includes:

a plurality of battery module strings configured to;

actuate the coupling units with the battery module strings

generate AC voltages, the AC voltages being phase-shifted with respect to one another and

determine the internal resistance with reference to the connections and decouplings of battery modules to generate the phase-shifted AC voltages.

10. A motor vehicle, comprising:

an electric motor; and

a battery system connected to the electric motor, the battery system including;

a battery including a battery module string having a plurality of series-connected battery modules, each of the battery modules having at least one battery cell, and an actuable coupling unit, each of the battery modules are configured to be selectively connected to and decoupled from the battery module string with the coupling units to generate a settable output voltage of the battery;

at least one monitoring unit configured to monitor the battery modules and measure at least one of cell voltages and battery module voltages;

at least one current measuring unit interconnected with the battery module string; and

a control and readout unit connected to (i) the coupling units, (ii) the at least one monitoring unit, and (iii) the at least one current measuring unit, the control and readout unit is configured to;

measure a first voltage of the at least one battery cell of a first battery module of the battery modules at a first time, wherein the first battery module is decoupled from a battery module string in response to a first control signal;

connect, in response to a second control signal, the first battery module to the battery module string after the first voltage measurement to enable a change in the first voltage of the at least one battery cell in response to a current flowing through the first battery module;

measure a second voltage of the at least one battery cell at a second time after the connection of the first battery module to the battery module string, wherein the first battery module is connected to the battery module string for a predefined time interval; and

determine the internal resistance after the measurement of the second voltage of the at least one battery cell with reference to (i) a difference between the first voltage and the second voltage and (ii) a current value of a current flowing through the first battery module.