Method for Determining the Actual Amount of Energy Available in an Energy Storage Module

• US 20100121592A1
• Filed: 01/19/2010
• Published: 05/13/2010
• Est. Priority Date: 07/20/2007
• Status: Active Grant

• Current Assignee: Bayerische Motoren Werke AG
• Original Assignee: Bayerische Motoren Werke AG
• Inventors: MAI, Alexander, HANDSCHUH, Tobias, REISCHL, Sebastian, FROESCHL, Joachim
• Granted Patent: US 8,265,891 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• 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: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/1423 with multiple batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

The amount of energy actually available in an energy storage module having a plurality of individual storage elements connected in series is determined. An upper and/or a lower limit voltage for the energy storage module is determined dynamically. During a charging operation of the energy storage module, in the event that a maximally permissible upper cell voltage is reached on at least one storage cell, the upper limit voltage of the energy storage module is determined by summing all cell voltages of all storage elements existing at that point-in-time. During a discharging operation, if a minimally permissible lower cell voltage is reached on at least one storage element, the lower limit voltage is determined by summing all cell voltages existing at that point-in-time. The actually available amount of energy is computed as a function of the determined limit voltage or voltages and of the determined actual storage capacity.

Claims

1. A method for determining an amount of energy actually available in an energy storage module having a plurality of individual storage cells connected in series, the method comprising the acts of:

determining dynamically at least one of an upper and a lower limit voltage for the energy storage module, wherein at least one of the following acts occur;

(a) during a charging operation of the energy storage module, upon reaching a maximally permissible upper cell voltage on at least one storage cell, the upper limit voltage of the energy storage module is determined by summing all cell voltages existing at that point-in-time for all of the plurality of individual storage cells; and

(b) during a discharging operation of the energy storage module, upon reaching a minimally permissible lower cell voltage on at least one storage cell, the lower limit voltage of the energy module is determined by summing all cell voltages existing at that point-in-time for all of the plurality of individual storage cells;

determining the amount of energy actually available in the energy storage module as a function of a determined actual storage capacity and at least one of the upper limit voltage and the lower limit voltage of the energy storage module.

2. The method according to claim 1, wherein the actual storage capacity of the energy storage module is determined by reading out a stored capacity value.

3. The method according to claim 2, wherein the stored capacity value is a variable capacity value.

4. The method according to claim 1, wherein the actual storage capacity of the energy storage module is determined by dynamically determining the capacity value by one of measuring and computing.

5. The method according to claim 1, wherein the act of determining the upper and/or the lower limit value of the energy storage module is carried out by reading out a stored voltage value.

6. The method according to claim 1, wherein the act of dynamically determining the upper and/or the lower limit voltage is carried out by at least one of measuring and computing.

7. The method according to claim 1, further comprising the act of:

generating a diagnostic signal as a function of a number of operating conditions of the energy storage module in which the minimally permissible lower cell voltage of a storage cell is reached within a predetermined time period or a particular operating mode of the electric system.

8. The method according to claim 1, wherein the energy storage module supplies an electric machine of a hybrid vehicle.

9. An electric system, comprising:

an energy storage module having a plurality of individual storage cells connected in series, the energy storage module being operatively configurable for supplying an electric machine of a hybrid vehicle;

a control unit operatively coupled with the energy storage module, the control unit including a computer readable medium containing program code segments that;

determines dynamically at least one of an upper and a lower limit voltage for the energy storage module, wherein at least one of the following acts occur;

(a) during a charging operation of the energy storage module, upon reaching a maximally permissible upper cell voltage on at least one storage cell, determine the upper limit voltage of the energy storage module by summing all cell voltages existing at that point-in-time for all of the plurality of individual storage cells; and

(b) during a discharging operation of the energy storage module, upon reaching a minimally permissible lower cell voltage on at least one storage cell, determine the lower limit voltage of the energy module by summing all cell voltages existing at that point-in-time for all of the plurality of individual storage cells;

determine the amount of energy actually available in the energy storage module as a function of a determined actual storage capacity and at least one of the upper limit voltage and the lower limit voltage of the energy storage module.