Method for precise power prediction for battery packs

• US 9,018,907 B2
• Filed: 10/08/2010
• Issued: 04/28/2015
• Est. Priority Date: 10/19/2009
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Boehm, Andre
• Primary Examiner(s): Siek, Vuthe
• Application Number:
  US13/499,145
• Publication Number:
  US 20120242289A1
• Time in Patent Office: 1,663 Days
• Field of Search: 320/118, 320/124, 320/125, 320/127, 320/135
• US Class Current: 320/118
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A method and apparatus for ascertaining the maximum power obtainable from a traction storage-battery system that includes a plurality of storage-battery elements connected in series. The method provides for: determining at least one power indicator for each storage-battery element, and ascertaining a quantity of the smallest power indicators of all determined power indicators of all storage-battery elements. The quantity includes the smallest power indicator or a subgroup thereof of all power indicators of the storage-battery elements. A power-output limit for the quantity is provided, starting from the power indicators of the quantity. The maximum power obtainable from the traction storage-battery system is extrapolated based on the power-output limit and linked by the extrapolation and because of the series connection, to a power output of the at least one storage-battery element for which the quantity of the smallest power indicators was ascertained.

Claims

1. A computer-implemented method for ascertaining a maximum obtainable power from a traction storage-battery system that includes a plurality of storage-battery elements connected in series, comprising:

determining, using at least one computer processor, at least one power indicator for each of the storage-battery elements;

ascertaining, by the at least one computer processor, a quantity of a smallest power indicators of all determined power indicators of all storage-battery elements, the quantity including one of a smallest power indicator or a subgroup of the smallest power indicators of all power indicators of the storage-battery elements;

providing a power-output limit for the quantity by operating the storage-battery system along the power-output limit of one of the storage-battery elements, by one of estimation or by approximation with the aid of a model that reflects the storage-battery elements, starting from the power indicators of at least one of the quantity and other measured physical instantaneous variables of the one of the storage-battery elements;

extrapolating the maximum power obtainable from the traction storage-battery system based on the power-output limit, the maximum power obtainable from the traction storage-battery system being linked by the extrapolation to a power output of the at least one storage-battery element for which the quantity of the smallest power indicators was ascertained, which lies by a predefined amount below the power-output limit; and

outputting the maximum power obtainable from the traction storage-battery system as a value,

wherein the extrapolation includes extrapolating the maximum obtainable power based on power output of at least one of weakest of the storage-battery elements for which the quantity of the smallest power indicators was ascertained, the extrapolation process extrapolating the maximum power obtainable from the total traction storage-battery system under a stipulation that the power output of the at least one of the weakest storage-battery elements within an overall assembly provided as the traction storage-battery system that includes all storage-battery elements, is not greater than the power-output limit minus a predefined amount, the predefined amount being greater than zero and corresponding at a maximum to a safety-factor power amount.

2. The method as recited in claim 1, wherein the ascertainment of the quantity includes ascertaining the smallest power indicator, the quantity being provided by the smallest power indicator, where the step of providing the power-output limit includes starting from the smallest power indicator, and the extrapolation is carried out based on power output of the storage-battery element having the smallest power indicator.

3. The method as recited in claim 1, wherein the determination of the power indicator includes measuring, as the power indication, at least one of a cell voltage which is available at the storage-battery elements, a load current with which the traction storage-battery system is loaded, a temperature which the storage-battery elements exhibit, an internal resistance of the storage-battery elements, a state of charge, and a cell capacity, and the determination of the power indicator further includes at least one of measuring at least one operating variable of the storage-battery elements, the operating variable being one of current, voltage or temperature, and ascertaining the power indicator by a model that simulates the storage-battery element.

4. The method as recited in claim 1, wherein the determination of the power indicator further includes repeated determination of the power indicator one of at different load currents with which the traction storage-battery system is loaded, or by repeated step-by-step increase of the load current and determining the power indicator for each stepwise increased load current.

5. The method as recited in claim 1, wherein the power-output limit is provided one of by comparing the power indicator to a predefined minimum power-indicator value, by forming the difference between the determined power indicator and the minimum power-indicator value, or by comparing cell voltage as power indicator of the quantity, to a minimum cell voltage as predefined minimum power indicator, the minimum cell voltage being a function of a type of the storage-battery elements and being less by a predefined voltage amount than a standard output voltage, and irreversible damage to the storage-battery elements occurring when the storage-battery elements are discharged to the standard output voltage minus the predefined voltage amount.

6. The method as recited in claim 1, wherein the maximum power obtainable from the traction storage-battery system is provided as one of a current value, or product of the current value and a total voltage of the traction storage-battery system;

the power output of the at least one of the weakest of the storage-battery elements is provided by the cell voltage of a weakest one of the storage-battery elements or by the cell-voltage sum of a plurality of the at least one weakest storage-battery elements;

the power-output limit is provided by a predefined minimum voltage amount which, in order to avoid irreversible damage, should not be undershot by any storage-battery element; and

the safety-factor power amount is provided by an additional voltage amount that corresponds to a safety margin which is defined by an estimated measuring-error scattering in cell-voltage measurement.

7. An apparatus for ascertaining a maximum power obtainable from a traction storage-battery system that includes a plurality of storage-battery elements connected in series, the apparatus comprising:

a voltage-measuring device, connected to each of the storage-battery elements, configured to measure voltage available at the storage-battery elements;

a current-measuring device, connected to the traction storage-battery system, configured to measure a current output by the traction storage-battery system;

a power-data acquisition device, connected to the voltage-measuring device and the current-measuring device, configured to one of provide a power indicator for all storage-battery elements based on voltage available at the respective storage-battery elements, provide a power indicator for all storage-battery elements based on internal resistances of the storage-battery elements resulting from the voltage available and output current, or provide a power indicator for one of the storage-battery elements having the smallest power indicator;

a comparator, connected to the power-data acquisition device, configured to compare the power indicators, and to ascertain at least one of the smallest power indicators; and

an extrapolation device which is connected to the comparator and which is set up to extrapolate the power-output limit of at least one of the storage-battery elements having the smallest power indicator based on the at least one of the smallest power indicators, and to extrapolate, based on the power-output limit, the maximum power obtainable from the traction storage-battery system, so that the maximum power obtainable from the traction storage-battery system is linked to a power output of the at least one storage-battery element which has the smallest power indicators, that lies by a predefined amount below the power-output limit,

wherein the extrapolation device is configured to extrapolate the maximum power obtainable based on power output of at least one of weakest of the storage-battery elements for which the quantity of the smallest power indicators was ascertained, the extrapolation device configured to extrapolate the maximum power obtainable from the total traction storage-battery system under a stipulation that the power output of the at least one of the weakest storage-battery elements within an overall assembly provided as the traction storage-battery system that includes all storage-battery elements, is not greater than the power-output limit minus a predefined amount, the predefined amount being greater than zero and corresponding at a maximum to a safety-factor power amount.

8. The apparatus as recited in claim 7, further comprising:

a temperature-measuring device, connected to the extrapolation device, configured to measure a temperature of the storage-battery elements, the extrapolation device including a model which, based on measured current, measured voltage and the measured temperature, estimates an operating state of the at least one of the storage-battery elements having the smallest power indicator, the operating state being reflected by at least one of a capacity, a state of charge, and an internal resistance, of the at least one of the storage-battery elements having the smallest power indicator.

9. The apparatus as recited in claim 7, wherein the comparator is configured to determine a smallest power indicator and the extrapolation device is configured to extrapolate the power-output limit of the one of the storage-battery elements having the smallest power indicator, and the extrapolation device further includes a multiplication device, the extrapolation device being configured to calculate, based on the power-output limit of the storage-battery element having the smallest power indicator and with the aid of the multiplication device, the maximum power obtainable as a product of the power-output limit and a number of storage-battery elements in the storage-battery system.