# US 11,994,561 B2 · Battery current limits estimation based on RC model

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- Number: US 11,994,561 B2
- Document ID: US11994561B2
- Status: Granted
- Kind: B2
- Application number: 18/327,991
- Filed: 2023-06-02
- Published: 2023-10-05
- Granted: 2024-05-28
- Earliest claimed: 2020-02-12
- Assignees: Karma Automotive LLC
- Applicants: Karma Automotive LLC
- Inventors: Jing Hong; Suvrat Ramasubramanian; Ali Jokar
- Web page: https://patentgrep.com/patent/US11994561B2

## CPC

- G01R 31/367: Software therefor, e.g. for battery testing using modelling or look-up tables
- G01R 31/382: Arrangements for monitoring battery or accumulator variables, e.g. SoC
- B60L 58/13: Maintaining the SoC within a determined range
- B60L 58/16: responding to battery ageing, e.g. to the number of charging cycles or the state of health [SoH]
- G01R 31/374: with means for correcting the measurement for temperature or ageing
- G01R 31/389: Measuring internal impedance, internal conductance or related variables
- G01R 31/392: Determining battery ageing or deterioration, e.g. state of health
- H02J 7/82: Control of state of charge [SOC]
- H02J 7/84: Control of state of health [SOH]
- B60L 2240/547: Voltage
- B60L 2240/549: Current
- G01R 19/16542: {for batteries (charge condition monitoring in G01R31/36)}
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A method of estimating a battery current limit for operation of a battery cell over the course of a specified prediction time. The method includes generating a plurality of current limit estimations by means of a plurality of current limit estimation sub-methods, wherein at least one current limit estimation sub-method generates its current limit estimation based on an RC equivalent circuit model of the battery cell, and determining the charge current limit by finding the lowest magnitude current limit estimation in the plurality of current limit estimations. At least one parameter of the RC equivalent circuit model is set based on the specified prediction time and at least one variable from the set of: a state of charge (SOC) of the battery cell, a temperature of the battery cell, a state of health (SOH) of the battery cell, a capacity of the battery cell, and a current of the battery cell.

## Claims

### Claim 1

A vehicle comprising:
a battery cell configured to power the vehicle; and
a battery management system in communication with the battery cell, the battery management system configured to:
generate a first discharge current limit estimation for operating the battery cell over a prediction time;
generate a second discharge current limit estimation for operating the battery cell over the prediction time; and
operate the battery cell to power the vehicle using the one of the first discharge current limit estimation or the second discharge current limit estimation associated with a lowest magnitude.

### Claim 2 (depends on 1)

The vehicle of claim 1, wherein the battery management system is configured to generate at least one of the first discharge current limit estimation or the second discharge current limit estimation based on an RC equivalent circuit model of the battery cell.

### Claim 3 (depends on 2)

The vehicle of claim 2, wherein at least one parameter of the RC equivalent circuit model is set based on the prediction time and at least one of a state of charge (SOC) of the battery cell, a temperature of the battery cell, a state of health (SOH) of the battery cell, a capacity of the battery cell, or a current of the battery cell.

### Claim 4 (depends on 1)

The vehicle of claim 1, wherein the battery management system is configured to:
generate the first discharge current limit estimation using one of a Hybrid Pulse Power Characterization (HPPC) method or a State of Charge (SOC) Limitation method; and
generate the second discharge current limit estimation using another one of the HPPC method or the SOC Limitation method.

### Claim 5 (depends on 4)

The vehicle of claim 4, wherein the HPPC method generates the first discharge current limit estimation or the second discharge current limit estimation based on an internal resistance of the battery cell as modeled by an RC equivalent circuit model of the battery cell.

### Claim 6 (depends on 1)

The vehicle of claim 1, wherein the battery management system is configured to:
generate the first discharge current limit estimation using one of a Hybrid Pulse Power Characterization (HPPC) method or an RC Model method; and
generate the second discharge current limit estimation using another one of the HPPC method or the RC Model method.

### Claim 7 (depends on 1)

The vehicle of claim 1, wherein the battery management system is configured to:
generate the first discharge current limit estimation using one of an RC Model method or a State of Charge (SOC) Limitation method; and
generate the second discharge current limit estimation using another one of the RC Model method or the SOC Limitation method.

### Claim 8 (depends on 1)

The vehicle of claim 1, wherein the battery management system is configured to generate the first discharge current limit estimation using an RC Model method.

### Claim 9 (depends on 8)

The vehicle of claim 8, wherein the RC Model method generates the first discharge current limit estimation by using parameters of an RC equivalent circuit model of the battery cell to find the first discharge current limit estimation according to the following equation:
I
k
=
V
t
,
k
-
OCV
k
-
U
1
,
k
-
1
⁢
e
-
Δ
⁢
t
/
(
R
1
⁢
C
1
)
-
U
2
,
k
-
1
⁢
e
-
Δ
⁢
t
/
(
R
2
⁢
C
2
)
R
0
,
k
+
R
1
,
k
(
1
-
e
-
Δ
⁢
t
/
(
R
1
⁢
C
1
)
)
+
R
2
,
k
(
1
-
e
-
Δ
⁢
t
/
(
R
2
⁢
C
2
)
)
where and U2,k-1 are U2,k-1 voltages across a first branch and a second branch of the RC equivalent model, Δt is an incremental sampling period of the battery cell measurement, k is a sampling step number, K is a number of sampling steps taken (such that 1≤k≤K and KΔt=tk), Ik is the first discharge current limit estimation, and Vt is a final voltage after the prediction time has elapsed.

### Claim 10 (depends on 9)

The vehicle of claim 9, wherein the final voltage comprises a minimum allowable battery cell voltage Vmin.

### Claim 11

A vehicle comprising:
a battery cell configured to power the vehicle; and
a battery management system in communication with the battery cell, the battery management system configured to:
generate a first charge current limit estimation for operating the battery cell over a prediction time;
generate a second charge current limit estimation for operating the battery cell over the prediction time; and
operate the battery cell to power the vehicle using the one of the first charge current limit estimation or the second charge current limit estimation associated with a lowest magnitude.

### Claim 12 (depends on 11)

The vehicle of claim 11, wherein the battery management system is configured to generate at least one of the first charge current limit estimation or the second charge current limit estimation based on an RC equivalent circuit model of the battery cell.

### Claim 13 (depends on 12)

The vehicle of claim 12, wherein at least one parameter of the RC equivalent circuit model is set based on the prediction time and at least one of a state of charge (SOC) of the battery cell, a temperature of the battery cell, a state of health (SOH) of the battery cell, a capacity of the battery cell, or a current of the battery cell.

### Claim 14 (depends on 11)

The vehicle of claim 11, wherein the battery management system is configured to:
generate the first charge current limit estimation using one of a Hybrid Pulse Power Characterization (HPPC) method or a State of Charge (SOC) Limitation method; and
generate the second charge current limit estimation using another one of the HPPC method or the SOC Limitation method.

### Claim 15 (depends on 14)

The vehicle of claim 14, wherein the HPPC method generates the first charge current limit estimation or the second charge current limit estimation based on an internal resistance of the battery cell as modeled by an RC equivalent circuit model of the battery cell.

### Claim 16 (depends on 11)

The vehicle of claim 11, wherein the battery management system is configured to:
generate the first charge current limit estimation using one of a Hybrid Pulse Power Characterization (HPPC) method or an RC Model method; and
generate the second charge current limit estimation using another one of the HPPC method or the RC Model method.

### Claim 17 (depends on 11)

The vehicle of claim 11, wherein the battery management system is configured to:
generate the first charge current limit estimation using one of an RC Model method or a State of Charge (SOC) Limitation method; and
generate the second charge current limit estimation using another one of the RC Model method or the SOC Limitation method.

### Claim 18 (depends on 11)

The vehicle of claim 11, wherein the battery management system is configured to generate the first charge current limit estimation using an RC Model method.

### Claim 19 (depends on 18)

The vehicle of claim 18, wherein the RC Model method generates the first charge current limit estimation by using parameters of an RC equivalent circuit model of the battery cell to find the first charge current limit estimation according to the following equation:
I
k
=
V
t
,
k
-
OCV
k
-
U
1
,
k
-
1
⁢
e
-
Δ
⁢
t
/
(
R
1
⁢
C
1
)
-
U
2
,
k
-
1
⁢
e
-
Δ
⁢
t
/
(
R
2
⁢
C
2
)
R
0
,
k
+
R
1
,
k
(
1
-
e
-
Δ
⁢
t
/
(
R
1
⁢
C
1
)
+
R
2
,
k
(
1
-
e
-
Δ
⁢
t
/
(
R
2
⁢
C
2
)
)
where U1,k-1 and U2,k-1 are voltages across a first branch and a second branch of the RC equivalent model, Δt is an incremental sampling period of the battery cell measurement, k is a sampling step number, K is a number of sampling steps taken (such that 1≤k≤K and KΔt=tk), Ik is the first discharge current limit estimation, and Vt is a final voltage after the prediction time has elapsed.

### Claim 20 (depends on 19)

The vehicle of claim 19, wherein the final voltage comprises a maximum allowable battery cell voltage Vmax.