Method of balancing batteries

• US 7,602,145 B2
• Filed: 07/18/2006
• Issued: 10/13/2009
• Est. Priority Date: 07/18/2006
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Motors Incorporated (Tesla Inc.)
• Inventors: Renda, Gregory Lee
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): Berhanu; Samuel
• Application Number:
  US11/488,353
• Publication Number:
  US 20080018299A1
• Time in Patent Office: 1,183 Days
• Field of Search: 320116-127
• US Class Current: 320/119
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/19 Switching between serial connection and parallel connection of battery modules
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A methodology for balancing batteries for use in an electric vehicle. The methodology includes initializing a target balance voltage value to a predetermined voltage. Sampling a first voltage of the batteries at a predetermined interval. Sending the lowest voltage value to all of the batteries. Replacing the target value voltage with the lowest voltage if the lowest voltage is lower than the target balance voltage and bleeding the batteries if a sampled voltage is higher than the target balance voltage.

Claims

1. A method of balancing voltage between batteries, said method including the steps of:

sampling a first voltage of one of the batteries at a predetermined interval;

initializing a target balance voltage value to a predetermined voltage for each battery;

sending said first voltage value to all other batteries;

replacing said target balance voltage with said first voltage if said first voltage is lower than said target balance voltage;

bleeding said battery if a sampled voltage is higher than said target balance voltage; and

replacing said target balance voltage if a predetermined time interval passes.

2. The method of claim 1 further including the step of determining if said sampled voltage is outside of a voltage delta.

3. The method of claim 2 wherein said voltage delta is approximately 20 millivolts.

4. The method of claim 1 further including the step of determining if battery is bled below a predetermined value.

5. A method of balancing batteries for use in a vehicle having a predetermined number of batteries being arranged in a brick, a predetermined number of bricks being arranged within a battery module and the vehicle having a predetermined number of battery modules therein, each battery module having a battery monitoring board, said method including the steps of:

sampling a first voltage for each brick at a predetermined time;

initializing each of the battery modules with a target balance voltage;

determining the lowest voltage for each battery module;

replacing said target balance voltage if said lowest voltage is lower than said target balance voltage;

bleeding one of the bricks if said first voltage is greater than said target balance voltage; and

periodically replacing said target balance voltage with the lowest voltage of all of the bricks within a specific battery module if a predetermined time interval passes.

6. The method of claim 5 wherein said step of initializing sets said target balance voltage with a lowest brick voltage for all bricks in said battery module.

7. The method of claim 5 further including the step of sending said lowest voltage for each battery module to all other batter modules.

8. The method of claim 7 further including the step of comparing said sent lowest voltage with said target balance voltage.

9. The method of claim 5 further including the step of comparing said target balance voltage to said voltage of each brick.

10. The method of claim 5 further including the step of determining if said voltage of each brick is outside of a predetermined voltage delta.

11. The method of claim 5 further including the step of determining if said voltage of each brick is less than a fixed minimum voltage level.

12. The method of claim 10 wherein said voltage delta is twenty millivolts.

13. The method of claim 7 wherein said step of sending occurs at an approximate 120 second interval.

14. The method of claim 6 wherein said step of periodically replacing said target balance voltage occurs at an approximate 240 second interval.

15. A method of balancing batteries for use in an electric vehicle, the module having a predetermined number of the batteries being arranged in a brick, a predetermined number of bricks being arranged within a battery module or sheet, the electric vehicle also having a predetermined number of battery modules or sheets, each battery module having an associated battery monitoring board which is in communication with every other battery monitoring board, said method including the steps of:

sampling a voltage for each brick at a predetermined time interval;

initializing a target balance voltage value in each battery monitoring board with an initial lowest brick voltage for the battery module controlled by each battery monitoring board;

sending an announced lowest brick voltage for each battery module to every other battery monitoring board;

comparing in each battery monitoring board said announced lowest brick voltage and said target balance voltage;

replacing said target balance voltage with said announced lowest brick voltage if said announced lowest brick voltage is less than said target balance voltage; and

bleeding any brick if said sampled voltage is greater than said target balance voltage and is outside of a predetermined voltage delta.

16. The method of claim 15 further including the step of determining if said sampled voltage or said target balance voltage is less than a fixed minimum voltage value.

17. The method of claim 15 further including the step of periodically replacing said target balance voltage with a lowest voltage of the bricks of each battery module if a predetermined time interval passes and at least one of said announced lowest brick voltage being less than or equal to said target balance voltage has not been received.

18. The method of claim 15 further including the step of bleeding said brick to said target balance voltage by inducing a predetermined sized load on said brick.