Battery formation/testing

Patent metadata

Field	Value
Publication number	US-11435404-B2
Application number	US-202017034588-A
Country	US
Kind code	B2
Filing date	Sep 28, 2020
Priority date	Sep 28, 2020
Publication date	Sep 6, 2022
Grant date	Sep 6, 2022

Abstract

Techniques for controlling a current of a battery cell during formation and/or testing are described. A current sensor is used to measure the current of the battery cell, which is used as a feedback signal for controlling the current to achieve a target current. The transfer function of the current sensor is used to improve the accuracy of the current measurement. Because the transfer function can be regularly determined during formation/testing, a lower-cost current sensor with relatively poor temperature coefficient may be used. Any change in the gain of the current sensor may be detected by the transfer function determination and corrected for. Therefore, high current control accuracy may be achieved at lower cost.

First claim

The invention claimed is:

1. A battery formation/testing controller for controlling a formation/testing current of a battery cell and for coupling to a current sensor arranged to output a measurement of battery cell current, the battery formation/testing controller being configured to:
determine a transfer function of the current sensor;
determine a current feedback measurement indicative of the formation/testing current of the battery cell, wherein determination of the current feedback measurement is based on the transfer function of the current sensor and the measurement of the battery cell current; and
control the formation/testing current of the battery cell based on a target formation/testing current and the determined current feedback measurement.

2. The battery formation/testing controller of claim 1 , wherein the current sensor comprises an analog-to-digital converter, ADC, having a non-linearity input range of input signals where analog input signals are converted non-linearly to digital output signals, the battery formation/testing controller further configured to:
compare the measurement of the battery cell current against the non-linearity input range; and
if the measurement of the battery cell current is outside of the non-linearity input range:
determine the transfer function of the current sensor.

3. The battery formation/testing controller of claim 1 , further configured to determine the transfer function of the current sensor by:
applying a reference input signal to the current sensor, such that the measurement of the battery cell current comprises a formation/testing current signal and a reference output signal corresponding to the reference input signal;
extracting the reference output signal from the measurement of the battery cell current; and
determining the transfer function based on the reference input signal and the reference output signal.

4. The battery formation/testing controller of claim 3 , wherein the current sensor comprises an analog-to-digital converter, ADC, and wherein the battery formation/testing controller is further configured to:
apply a dither to the reference input signal.

5. The battery formation/testing controller of claim 4 , wherein applying the dither to the reference input signal comprises:
transposing the reference input signal between at least two signal levels.

6. The battery formation/testing controller of claim 4 , wherein applying the dither to the reference input signal comprises:
modulating an amplitude of the reference input signal.

7. The battery formation/testing controller of claim 1 , further configured to:
read the transfer function of the current sensor from memory.

8. The battery formation/testing controller of claim 7 , further configured to:
determine a further transfer function of the current sensor;
determine a further current feedback measurement based on the further transfer function and a further measurement of the battery cell current output by the current sensor; and
control the formation/testing current of the battery cell based on the target formation/testing current and the determined further current feedback measurement.

9. The battery formation/testing controller of claim 8 , further configured to:
store in memory the further transfer function for use in determining future current feedback measurements.

10. The battery formation/testing controller of claim 1 , further configured to control the formation/testing current of the battery cell by:
controlling operation of one or more transistors configured to control a magnitude of the formation/testing current.

11. The battery formation/testing controller of claim 1 , wherein the formation/testing current is a charging current applied to the battery cell or a discharge current output from the battery cell.

12. The battery formation/testing controller of claim 1 , further configured to:
determine a voltage feedback measurement indicative of the formation/testing voltage across the battery cell, wherein determination of the voltage feedback measurement is based on a transfer function of a voltage sensor coupled across the battery cell and a measurement of the voltage across the battery cell from the voltage sensor; and
control the formation/testing voltage across the battery cell based on a target formation/testing voltage and the determined voltage feedback measurement.

13. A battery formation/testing system comprising:
an analog-to-digital converter, ADC, for coupling to a current transducer that is arranged to generate an analog signal indicative of a battery cell current of a battery cell; and
a battery formation/testing controller coupled to a digital output of the ADC and configured to:
determine a transfer function of a current sensor;
determine a current feedback measurement indicative of a formation/testing current of the battery cell, wherein determination of the current feedback measurement is based on the transfer function of a current sensor and the digital output of the ADC; and
control the formation/testing current of the battery cell based on a target formation/testing current and the determined current feedback measurement.

14. The battery formation/testing system of claim 13 , wherein the current transducer comprises a shunt resistor.

15. The battery formation/testing system of claim 13 , wherein the battery formation/testing controller is configured to:
read the transfer function of the current sensor from memory.

16. The battery formation/testing system of claim 15 , wherein the battery formation/testing controller is further configured to:
determine a further transfer function of the current sensor;
determine a further current feedback measurement based on the further transfer function and a further measurement of the battery cell current output by the current sensor; and
control the formation/testing current of the battery cell based on the target formation/testing current and the determined further current feedback measurement.

17. A method for controlling a formation/testing current of a battery cell, the method comprising:
determining a transfer function of a current sensor;
determining a current feedback measurement indicative of the formation/testing current of the battery cell, wherein determination of the current feedback measurement is based on:
a transfer function of the current sensor that is arranged to output a measurement of battery cell current; and
the measurement of battery cell current; and

controlling the formation/testing current of the battery cell based on a target formation/testing current and the determined current feedback measurement.

18. The method of claim 17 , wherein the current sensor comprises an analog-to-digital converter, ADC, having a non-linearity input range of input signals where analog input signals are converted non-linearly to digital output signals, the method further comprising:
comparing the measurement of the battery cell current against the non-linearity input range; and
if the measurement of the battery cell current is outside of the non-linearity input range:
determining the transfer function of the current sensor.

19. The method of claim 17 , further configured to determine the transfer function of the current sensor by:
applying a reference input signal to the current sensor, such that the measurement of the battery cell current comprises a formation/testing current signal and a reference output signal corresponding to the reference input signal;
extracting the reference output si

Assignees

• Analog Devices International Unlimited Co

Inventors

• Ye Shaoli
• Kelso Gina M
• Lath David J
• Holland William Michael James
• O'Donnell John Jude

Classifications

• H01M10/446

  Initial charging measures · CPC title

• G01R31/3648

  comprising digital calculation means, e.g. for performing an algorithm · CPC title

• G01R31/3865 Primary

  related to manufacture, e.g. testing after manufacture · CPC title