Method and system for battery state of charge estimation by using measured changes in voltage

• US 7,098,666 B2
• Filed: 07/28/2004
• Issued: 08/29/2006
• Est. Priority Date: 07/28/2004
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Patino, Joseph
• Primary Examiner(s): Benhane, Adolf Deneke
• Assistant Examiner(s): PIGGUSH, AARON C
• Application Number:
  US10/900,600
• Publication Number:
  US 20060022677A1
• Time in Patent Office: 762 Days
• Field of Search: 324/430, 324/431, 324/433, 324/429, 320/152, 320/153, 320/151, 320/156
• US Class Current: 324/433
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3835 involving only voltage measurements

Abstract

A method (20 or 30) and system (40) for estimating a battery state of charge can include a memory (48) for storing at least one among an impedance value, a plurality of values for V drop 0-1, or a plurality of values for V drop 0-1 normalized for charge or discharge values providing a stored plurality of values. The system can include a processor (44) and can measure at least one among V drop C-0 providing a measured V drop C-0 value and V drop 0-1 for the providing a measured V drop 0-1 value. The processor can be programmed to perform the functions of dividing the V drop C-0 value by the impedance value to estimate a charging current at the battery or comparing the measured V drop 0-1 value with a value among the stored plurality of values to estimate the battery state of charge.

Claims

1. A method of estimating a battery state of charge, comprising the steps of:

measuring a battery voltage when a charger is on;

measuring a battery voltage when the charger is subsequently turned off;

calculating a difference between the battery voltage when the charger is on and when the charger is subsequently turned off;

dividing the difference by an impedance value stored in a memory to estimate a current that the battery is being charged at; and

storing a plurality of values that are an ohmic measurement proportional to R1C1 in a battery cell model represented as 2 sets of series RC elements in parallel.

2. The method of claim 1, wherein the method further comprises the step of updating a charge indicator on an electronic device using the current that has been estimated.

3. The method of claim 1, wherein the method further comprises the step of storing the impedance value in a EPROM.

4. The method of claim 1, wherein the method further comprises the step of temperature compensating the plurality of values.

5. The method of claim 2, wherein the step of updating the charge indicator comprises the step of updating a fuel bar.

6. The method of claim 1, wherein the difference in battery voltage is calculated at the moment between when a charge current was being applied and when the charge current is removed from the battery.

7. A method of estimating a battery state of charge in an electronic device, comprising the steps of:

storing at least one among a plurality of values for V drop 0-1 for a given battery and a plurality of values for V drop 0-1 for the given battery normalized for charge or discharge values providing a stored plurality of values;

measuring V drop 0-1 for the given battery providing a measured V drop 0-1 value, wherein measuring V drop 0-1 includes measuring a voltage drop associated with R2C2 and a normalized voltage drop to charge/discharge currents in a battery cell model represented as 2 sets of series RC elements in parallel; and

comparing the measured V drop 0-1 value with at least one value among the stored plurality of values to estimate the battery state of charge.

8. The method of claim 7, wherein the method further comprises the step of temperature compensating the stored plurality of values.

9. The method of claim 7, wherein the step of comparing occurs in one among a charge mode and a discharge mode.

10. A system for estimating a battery state of charge, comprising:

a memory for storing at least one among an impedance value, a plurality of values for V drop 0-1 and a plurality of values for V drop 0-1 for a given battery normalized for charge or discharge values providing a stored plurality of values

a measuring device measuring at least one among V drop C-0 for the given battery providing a measured V drop C-0 value and V drop 0-1 for the given battery providing a measured V drop 0-1 value, wherein measuring V drop 0-1 includes measuring a voltage drop associated with R2C2 and a normalized voltage drop to charge/discharge currents in a battery cell model represented as 2 sets of series RC elements in parallel; and

a processor programmed to perform at least one among the functions of;

dividing the V drop C-0 value by the impedance value to estimate a current that the battery is being charged at; and

comparing the measured V drop 0-1 value with at least one value among stored plurality of values to estimate the battery state of charge.

11. The system of claim 10, wherein the memory comprises an EPROM.

12. The system of claim 10, wherein V drop C-0 comprises a difference between a battery voltage when a charger is on and when the charger is turned off.

13. The system of claim 10, wherein V drop 0-1 comprises a battery voltage delta (V drop) from the moment that the charge current is removed from the battery (0) to some duration of time thereafter (1).

14. The system of claim 10, wherein at least one among the memory, the measuring device, and the processor resides within at least one among a battery and an electronic device.

15. The system of claim 14, wherein the electronic device is selected among the group comprising a cellular phone, a shaver, a charging device, a two-way radio, a cordless telephone, a cordless toothbrush, a cordless hand tool.

16. The system of claim 12, wherein the charger is a wireless charger.

17. The system of claim 13, wherein the charger is a wireless charger.