APPARATUS AND METHOD FOR DISCHARGING A BATTERY AND DETERMINING A CONDITION OF THE BATTERY

• US 20140132223A1
• Filed: 11/13/2012
• Published: 05/15/2014
• Est. Priority Date: 11/13/2012
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola Solutions, Inc.
• Inventors: Kerfoot, Roy L. Jr., Geren, Michael D., Herrmann, John E.
• Granted Patent: US 9,097,775 B2
• Time in Patent Office: Days
• US Class Current: 320/136
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A method and apparatus for determining the condition of a rechargeable battery determines a dynamic impedance of the battery while discharging the battery, and determines a battery condition category based on the dynamic impedance. The battery can be discharged in a manner that recovers the stored energy being discharged from the battery.

Claims

1. A method for discharging a rechargeable battery, comprising:

discharging a rechargeable battery;

monitoring a dynamic battery current and a dynamic battery voltage of the rechargeable battery while discharging the rechargeable battery;

determining a dynamic impedance of the rechargeable battery responsive to monitoring the dynamic battery current and the dynamic battery voltage; and

determining a battery condition category by categorizing the dynamic impedance into one of a plurality of battery condition categories.

2. The method of claim 1, further comprising writing the battery condition category into a memory of the rechargeable battery.

3. The method of claim 1, wherein monitoring the dynamic battery current and dynamic battery voltage comprises:

applying a first load to a rechargeable battery determining a first current and a first battery voltage provided by the rechargeable battery responsive to applying the first load;

applying a second load to the rechargeable battery;

determining a second current and a second battery voltage provided by the rechargeable battery responsive to applying the second load;

wherein the dynamic impedance is determined as a ratio of the difference between the first battery voltage and the second battery voltage and the difference between the first current and the second current.

4. The method of claim 1, wherein the discharging is performed by a modular discharging unit having an internal load network and a modular interface to interface with a plurality of external load modules, discharging the rechargeable battery comprises:

determining that at least one external load module is connected to the modular discharging unit; and

selecting either the internal load network or the external load module for discharging the rechargeable battery.

5. The method of claim 4, wherein the selecting either the internal load network or the external load module for discharging the rechargeable battery is performed based on a capacity of the rechargeable battery.

6. The method of claim 4, wherein the selecting either the internal load network or the external load module for discharging the rechargeable battery comprises selecting an external module having a storage load that is charged by discharging the rechargeable battery through the storage load.

7. The method of claim 6, selecting an external module having a storage load comprises selecting an external module having an alternating current (AC) inverter coupled to the storage load that provides standard AC service from the storage load.

8. The method of claim 1, further comprising visually indicating the battery condition category.

9. A battery discharger, comprising:

a battery connector interface configured to connect the battery discharger to a rechargeable battery including positive and negative contacts and a data contact;

an internal load network configured to produce a variable load;

a controller having a data port coupled to the data contact and operable to vary the load of the internal load network;

a current sense circuit operable to indicate a current level through the internal load network to the controller;

a voltage sense circuit operable to indicate a voltage level between the positive and negative contacts to the controller; and

the controller is further operable to vary the internal load network to monitor a dynamic battery current and a dynamic battery voltage of a rechargeable battery, determine a dynamic impedance of the rechargeable battery from the dynamic battery current and the dynamic battery voltage, and determine a battery condition category based on the dynamic impedance.

10. The battery discharger of claim 9, wherein the controller is further operable to write the battery condition category into a memory of the rechargeable battery.

11. The battery discharger of claim 9, further comprising a modular interface configure to connect to an external load module.

12. The battery discharger of claim 9, wherein the controller determines the dynamic battery impedance by applying a first load of the variable load network to a rechargeable battery and determining a first current and a first battery voltage provided by the rechargeable battery responsive to applying the first load;

applying a second load of the variable load network to the rechargeable battery, and determining a second current and a second battery voltage provided by the rechargeable battery responsive to applying the second load; and

wherein the dynamic impedance is determined by the controller as a ratio of the difference between the first battery voltage and the second battery voltage and the difference between the first current and the second current.

13. The battery discharger of claim 11, the controller is further operable to determine that at least one external load module is connected to the battery discharger;

and

select either the internal load network or the external load module for discharging the rechargeable battery.

14. The battery discharger of claim 13, wherein the controller determines a capacity of the rechargeable battery and selects either the internal load network or the external load module for discharging the rechargeable battery based on a capacity of the rechargeable battery.

15. The battery discharger of claim 9, further comprising a visual display element, and wherein the controller is further configured to indicate the battery condition via the visual display element.

16. A modular battery discharging system, comprising:

a battery discharger configured to connect to a rechargeable battery and discharge the rechargeable battery, and including a variable load network operable to determine a dynamic impedance of the rechargeable battery and to determine a battery condition based on the dynamic battery impedance, the battery discharger further including a modular interface;

at least one external discharging module configured to be connected to the modular interface, and having a load for discharging the rechargeable battery; and

the battery discharger is operable to discharge the rechargeable battery through the internal load network, the at least on external discharging module, or both.

17. The modular battery discharging system of claim 16, wherein the battery discharger is further operable to write the battery condition into a memory of the rechargeable battery.

18. The modular battery discharging system of claim 16, wherein the at least one external discharging module comprises a storage load.

19. The modular battery discharging system of claim 18, wherein the at least one external discharging unit comprising the storage load further comprises an alternating current (AC) inverter operable to produce a standard AC service from the storage load.

20. The modular battery discharging system of claim 19, wherein the at least one external discharging unit comprising the storage load further comprising a buck/boost regulator through which the rechargeable battery discharges into the storage load.