Method for determining the charge in a vehicle battery

• US 10,150,460 B2
• Filed: 09/03/2013
• Issued: 12/11/2018
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Jaguar Land Rover Limited (TATA Motors Limited)
• Original Assignee: Jaguar Land Rover Limited (TATA Motors Limited)
• Inventors: Slosarczyk, Krzysztof, Lages, Fernando, Cockings, Kevin, Pickering, Stephen, Mikos, Jakub
• Primary Examiner(s): Smith, Jelani A
• Assistant Examiner(s): Williams, Kelly D
• Application Number:
  US14/426,200
• Publication Number:
  US 20150232081A1
• Time in Patent Office: 1,925 Days
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 2510/06 Combustion engines, Gas turbines
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: B60W 2710/248 Current for loading or unloading
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: H02J 7/1423 with multiple batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A method for determining the charge in a battery which comprises providing a main battery and a auxiliary battery. The method then comprises connecting the main battery to an electrical load; measuring I₁, the current drawn from the main battery while it is connected to the electrical load; connecting the auxiliary battery in parallel with the main battery and the electrical load; measuring I₂, the current drawn from the main battery while it is connected to the electrical load and the auxiliary battery; and estimating the state of charge in the auxiliary battery based upon at least the difference between I₁ and I₂.

Claims

1. A method for determining the state of charge in a battery, the method comprising:

connecting a main battery to an electrical load;

measuring I₁, which is current drawn from the main battery while it is connected to the electrical load;

connecting an auxiliary battery in parallel with the main battery and the electrical load;

measuring I₂, which is current drawn from the main battery while it is connected to the electrical load and the auxiliary battery; and

estimating a state of charge in the auxiliary battery based upon a difference between the measured I₁ and the measured I₂.

2. The method of claim 1, further comprising:

taking a plurality of measurements of I₁ and I₂; and

deriving a plurality of estimates of the state of charge in the auxiliary battery using the plurality of measurements of I₁ and I₂.

3. The method of claim 1, further comprising:

determining a temperature of the main battery; and

estimating the state of charge in the auxiliary battery based upon at least the difference between I₁ and I₂, and the temperature of the main battery.

4. The method of claim 1, further comprising:

determining a temperature of the auxiliary battery; and

estimating the state of charge in the auxiliary battery based upon at least the difference between I₁ and I₂, and the temperature of the auxiliary battery.

5. The method of claim 1, further comprising:

initiating a charging cycle for the auxiliary battery if the estimated state of charge in the auxiliary battery is beneath a predetermined level.

6. The method of claim 1, further comprising:

determining a size of the electrical load; and

in dependence on the size of the electrical load being beneath a predetermined threshold, interrupting the method of claim 1 until the size of the electrical load has risen above the predetermined threshold.

7. The method of claim 1, further comprising:

determining a size of the electrical load; and

in dependence on the size of the electrical load exceeding a predetermined maximum, interrupting the method of claim 1.

8. The method of claim 1, further comprising:

calculating a current contribution ratio C, where C=I₂/(I₁−

I₂); and

estimating the state of charge in the auxiliary battery based upon at least the value of C.

9. The method of claim 8, wherein estimating the state of charge in the auxiliary battery comprises comparing C to a threshold value of C.

10. The method of claim 1, further comprising:

providing a table which relates the difference between I₁ and I₂ with a state of charge in the auxiliary battery; and

using the table to estimate the state of charge in the auxiliary battery.

11. The method of claim 10, comprising calibrating the table by:

not charging or discharging the auxiliary battery for a predetermined period of time;

measuring a voltage across terminals of the auxiliary battery;

estimating the state of charge in the auxiliary battery based upon a voltage across the terminals;

comparing the estimate of the state of charge of the auxiliary battery based upon the voltage across the terminals with the estimate of the state of charge of the auxiliary battery based upon the difference between the measured I₁ and the measured I₂; and

amending the table so that the two estimates are the same.

12. A power management system comprising:

a control unit;

a main battery; and

an auxiliary battery,

the control unit configured to estimate a state of charge of the auxiliary battery using the method of claim 1.

13. A vehicle comprising the power management system of claim 12.

14. A vehicle comprising a control unit configured to perform the method of claim 1.

15. A vehicle comprising an electrical load and main and auxiliary batteries independently connectible by a control unit to the electrical load and at least one battery monitoring system configured to measure current (I) drawn by the electrical load from the main battery, wherein the control unit is configured to:

connect the main battery to the electrical load,

determine I₁, which is current drawn from the main battery while it is connected to the electrical load,

connect the auxiliary battery in parallel with the main battery to the electrical load,

measure I₂, which is current drawn from the main battery while it is connected to the electrical load and the auxiliary battery, and

estimate a state of charge in the auxiliary battery based upon at least the difference between I₁ and I₂.

16. The vehicle of claim 15, wherein the vehicle incorporates an internal combustion engine and has a stop start mode of operation whereby the main battery is employed to start the engine and operate the vehicle electrical load while the engine is running and the auxiliary battery is employed to operate the vehicle electrical load while the engine is being started by the main battery during said stop start mode of operation, wherein said control unit is arranged to estimate the state of charge of the auxiliary battery while the engine is running.