# US 2019/0170826 A1 · Battery state-of-health determination upon charging

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- Number: US 2019/0170826 A1
- Document ID: US20190170826A1
- Status: Published application
- Kind: A1
- Application number: 16/211,995
- Filed: 2018-12-06
- Published: 2019-06-06
- Earliest claimed: 2017-12-06
- Applicants: Cadex Electronics Inc.
- Inventors: Tina Shoa Hassani Lashidani
- Web page: https://patentgrep.com/patent/US20190170826A1

## CPC

- G01R 31/392: Determining battery ageing or deterioration, e.g. state of health
- G01R 31/3648: {comprising digital calculation means, e.g. for performing an algorithm}
- G01R 31/367: Software therefor, e.g. for battery testing using modelling or look-up tables
- G01R 31/3835: involving only voltage measurements
- H02J 7/865: {Battery or charger load switching, e.g. concurrent charging and load supply (H02J7/50 takes precedence)}
- H02J 7/90: Regulation of charging or discharging current or voltage
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY

## Abstract

A rechargeable battery is charged and at the same time, steps are taken to assess its state of health. The state of charge is first estimated, then repeatedly measured and predicted during charging until its value converges to a reliable value. A further known state of charge is later determined, during or after the remainder of the charging. Using the two states of charge and the amount of charge supplied to the battery, the state of health is calculated based on the rated capacity of the battery.

## Claims

### Claim 1

A method of determining state of health (SoH) of a battery of rated capacity C comprising the steps of:
estimating an initial value of a state of charge (SoC) of the battery;
starting to charge the battery;
repeatedly measuring a voltage across terminals of the battery as the battery is charged;
obtaining a converged value (SoCC) of the SoC from the repeated measurements;
determining a later value (SoC2) of the SoC after further charging the battery;
determining a charge (Q2) supplied to the battery between SoCC and SoC2;
calculating, using SoC2, SoCC, Q2 and C, a value of the SoH of the battery.

### Claim 2 (depends on 1)

The method of claim 1 further comprising:
determining a charge (Qi) supplied to the battery between starting to charge the battery and SoCC; and
calculating a refined value (SoCi) of the initial SoC using Q1, Q2, SoCC and SoC2;
wherein the SoH is calculated as (Q1+Q2)/[C(SoC2−SoCi)].

### Claim 3 (depends on 1)

The method of claim 1 wherein the SoH is calculated as Q2/[C(SoC2−SoCC)].

### Claim 4 (depends on 1)

The method of claim 1, wherein SoC2 is 100%.

### Claim 5 (depends on 1)

The method of claim 1, wherein the battery is fully discharged when the initial value of the SoC is estimated.

### Claim 6 (depends on 1)

The method of claim 1, wherein estimating the initial value of the SoC comprises:
measuring an open circuit voltage (OCV) of the battery to result in value V; and
using V to determine the initial value by accessing a relationship between the OCV and SoC, the relationship being represented by a graph, an analytic function or a table.

### Claim 7 (depends on 6)

The method of claim 6, wherein the relationship is defined by a 10th order polynomial.

### Claim 8 (depends on 7)

The method of claim 7, wherein the 10th order polynomial represents an average of OCV and SoC data measured during charging and discharging the battery or another battery that is comparable to the battery.

### Claim 9 (depends on 7)

The method of claim 7 comprising:
charging the battery fully at a rate of C/15 or lower;
discharging the battery fully at a rate of C/15 or lower;
deriving the 10th order polynomial from data recorded said charging and discharging;
subsequently charging the battery while recording further data; and
fitting the further data to an electrical circuit model of the battery that is used to predict the voltage across the terminals.

### Claim 10 (depends on 1)

The method of claim 1, comprising:
repeatedly predicting values of the voltage across the terminals using a Kalman filter;
repeatedly comparing the predicted values with the measured voltages; and
determining that a difference between the predicted values and the measured voltages is below a threshold;
wherein the SoCC is obtained when said difference is below the threshold.

### Claim 11 (depends on 10)

The method of claim 10, wherein the voltage across the terminals is predicted using an electric circuit model of the battery, a current supplied to the battery and a 10th order polynomial relationship between the OCV and SoC.

### Claim 12 (depends on 11)

The method of claim 11, comprising automatically selecting the electric circuit model from a choice of multiple electric circuit models using an interacting multiple model algorithm.

### Claim 13 (depends on 11)

The method of claim 11, wherein the electric circuit model is a first, second or third order model.

### Claim 14 (depends on 11)

The method of claim 11, wherein a particle-swarm method is used to extract parameters from the electric circuit model for use in prediction of the voltage across the terminals.

### Claim 15 (depends on 10)

The method of claim 10, wherein the difference is a root mean square difference of multiple sequential comparisons of the predicted values and the measured voltages.

### Claim 16 (depends on 10)

The method of claim 10, wherein:
the battery is charged with constant current; and
the voltage across the terminals is predicted using a polynomial.

### Claim 17 (depends on 1)

The method of claim 1, wherein the voltage across the terminals is measured multiple times per second.

### Claim 18 (depends on 1)

The method of claim 1 comprising, prior to charging the battery, categorizing the SoH of the battery as good, medium or poor;
wherein estimating the initial value of the SoC comprises:
measuring an open circuit voltage (OCV) of the battery to result in value V; and
using V to determine the initial value by accessing a relationship between the OCV and SoC, the relationship being defined by a corresponding one of three different 10th order polynomials, each polynomial representing a good, medium or poor SoH.

### Claim 19 (depends on 1)

The method of claim 1, wherein the battery is charged with a constant current.

### Claim 20 (depends on 1)

The method of claim 1, wherein the SoCC is obtained when the battery is being charged in constant voltage mode, and the further charging occurs in constant voltage mode.

### Claim 21 (depends on 1)

The method of claim 1, comprising:
obtaining multiple converged values of the SoC of the battery;
creating a graph of the multiple converged values of the SoC against charge supplied to the battery; and
calculating a slope (S) of the graph;
wherein the SoH is calculated as 1.0/SC.

### Claim 22

A battery charger for determining state of health (SoH) of a battery of rated capacity C comprising:
a battery interface that connects to the battery;
a user interface;
a processor connected to the battery interface and the user interface;
a computer readable memory storing computer readable instructions, which, when executed by the processor, cause the battery charger to:
estimate an initial value of a state of charge (SoC) of the battery;
start to charge the battery;
repeatedly measure a voltage across terminals of the battery as the battery is charged;
obtain a converged value (SoCC) of the SoC from the repeated measurements;
determine a later value (SoC2) of the SoC after further charging the battery;
determine a charge (Q2) supplied to the battery between SoCC and SoC2;
calculate, using SoC2, SoCC, Q2 and C, a value of the SoH of the battery; and
output the calculated value of the SoH on the user interface.

### Claim 23 (depends on 22)

The battery charger of claim 22, configured to estimate the initial value of the SoC by:
measuring an open circuit voltage (OCV) of the battery to result in value V; and
using V to determine the initial value by accessing a 10th order polynomial relationship between the OCV and SoC;
and further configured to:
repeatedly predict values of the voltage across the terminals using a Kalman filter;
repeatedly compare the predicted values with the measured voltages; and
determine that a difference between the predicted values and the measured voltages is below a threshold;
wherein the SoCC is obtained when said difference is below the threshold.

### Claim 24 (depends on 23)

The battery charger of claim 23, wherein the battery interface is a battery adapter and the Kalman filter is stored in the battery adapter.

### Claim 25 (depends on 23)

The battery charger of claim 23, further comprising an interface to an internet-based server, wherein the Kalman filter is stored on the server.

### Claim 26 (depends on 22)

The battery charger of claim 22, wherein the battery charger is an ultra-fast charger and configured to control a rate of charging using an estimate of the SoC obtained during charging.