Systems and methods for battery reactive impedance measurements

1 . A method comprising:

measuring a voltage of a battery cell;

measuring a current flowing through the battery cell;

selecting a plurality of candidate time offsets;

generating a plurality of datasets for the plurality of candidate time offsets;

determining a plurality of standard deviations for the plurality of datasets;

determining a time offset based on the plurality of standard deviations;

shifting the current based on the determined time offset;

sampling the voltage and the shifted current based on the determined time offset; and

determining an impedance of the battery cell based on the sampled voltage and the sampled shifted current.

2 . The method of claim 1 , further comprising injecting a stimulation signal to the battery cell, wherein the stimulation signal is one of the current and the voltage.

3 . The method of claim 1 , wherein the plurality of candidate time offsets comprises three candidate time offsets, the plurality of datasets comprises three datasets and the plurality of standard deviations comprises three standard deviations.

4 . The method of claim 1 , wherein the plurality of candidate time offsets are within a predefined time range.

5 . The method of claim 1 , wherein generating the plurality of datasets comprises, for each one of the candidate time offset:

shifting the current by a candidate time offset;

sampling the voltage and the current based on the candidate time offset; and

dividing the sampled voltage by the sampled current to generate a dataset corresponding to the candidate time offset.

6 . The method of claim 1 , wherein determining the time offset based on the plurality of standard deviations comprises:

performing linear approximation on the plurality of standard deviations to identify a minimum standard deviation that corresponds to the time offset.

7 . The method of claim 1 , wherein determining the impedance of the battery cell based on the sampled voltage and sampled shifted current comprises:

generating a dataset corresponding to the time offset;

determining an average of values in the dataset; and

setting the average as the impedance.

8 . A semiconductor device comprising a controller configured to:

obtain a voltage of a battery cell;

obtain a current flowing through the battery cell;

select a plurality of candidate time offsets;

generate a plurality of datasets for the plurality of candidate time offsets;

determine a plurality of standard deviations for the plurality of datasets;

determine a time offset based on the plurality of standard deviations;

shift the current based on the determined time offset;

sample the voltage and the shifted current based on the determined time offset; and

determine an impedance of the battery cell based on the sampled voltage and the sampled shifted current.

9 . The semiconductor device of claim 8 , wherein the controller is configured to inject a stimulation signal to the battery cell, and the stimulation signal is one of the current and the voltage.

10 . The semiconductor device of claim 8 , wherein the plurality of candidate time offsets comprises three candidate time offsets, the plurality of datasets comprises three datasets and the plurality of standard deviations comprises three standard deviations.

11 . The semiconductor device of claim 8 , wherein the plurality of candidate time offsets are within a predefined time range.

12 . The semiconductor device of claim 8 , wherein the controller is configured to, for each one of the candidate time offset:

shift the current by a candidate time offset;

sample the voltage and the current based on the candidate time offset; and

divide the sampled voltage by the sampled current to generate a dataset corresponding to the candidate time offset.

13 . The semiconductor device of claim 8 , wherein the controller is configured to:

perform linear approximation on the plurality of standard deviations to identify a minimum standard deviation that corresponds to the time offset.

14 . The semiconductor device of claim 8 , wherein the controller is configured to:

generate a dataset corresponding to the time offset;

determine an average of values in the dataset; and

set the average as the impedance.

15 . A system comprising:

a battery cell;

a cell monitor configured to measure a voltage of the battery cell;

a pack monitor configured to measure a current flowing through the battery cell; and

a controller configured to:

select a plurality of candidate time offsets;

generate a plurality of datasets for the plurality of candidate time offsets;

determine a plurality of standard deviations for the plurality of datasets;

determine a time offset based on the plurality of standard deviations;

shift the current based on the determined time offset;

sample the voltage and the shifted current based on the determined time offset; and

determine an impedance of the battery cell based on the sampled voltage and the sampled shifted current.

16 . The system of claim 15 , wherein the controller is configured to:

perform linear approximation on the plurality of standard deviations to identify a minimum standard deviation that corresponds to the time offset.

17 . The system of claim 16 , wherein the plurality of candidate time offsets comprises three candidate time offsets, the plurality of datasets comprises three datasets and the plurality of standard deviations comprises three standard deviations.

18 . The system of claim 15 , wherein the controller is configured to:

generate a dataset corresponding to the time offset;

determine an average of values in the dataset; and

set the average as the impedance.