Time-based vehicle battery balancing system and method

• US 8,676,419 B2
• Filed: 07/28/2011
• Issued: 03/18/2014
• Est. Priority Date: 07/28/2011
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Blakemore, Bruce Carvell, Gale, Allan Roy, Elie, Larry Dean
• Primary Examiner(s): Shafi, Muhammad
• Application Number:
  US13/192,513
• Publication Number:
  US 20130030618A1
• Time in Patent Office: 964 Days
• Field of Search: 701/22, 701/36, 320/132, 320/136, 320/135, 320/166, 320/162, 324/427, 324/430, 324/116, 324/124, 324/134, 429/99, 429/61, 429/100, 429/153, 429/163
• US Class Current: 701/22
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/80 Time limits
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 53/14 Conductive energy transfer
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

A power system for a vehicle may include at least one controller and a battery having a plurality of cells. The at least one controller may, for each of the cells, determine a voltage of the cell, determine a discharge time to reduce the voltage to a value approximately equal to a minimum of the determined voltages, and cause the cell to discharge for the discharge time to balance the battery.

Claims

1. A vehicle comprising:

an electric machine configured to generate motive power for the vehicle;

a battery including a plurality of cells configured to store energy for the electric machine; and

at least one controller configured to discharge each of the cells for a predetermined cell discharge time to reduce a current voltage of each of the cells to a target voltage to balance the battery, wherein each of the predetermined cell discharge times (t) is based on a resistance (R) of resistive circuitry associated with the cell, an equivalent capacitance (C) of the cell, the current voltage (v_current) of the cell, and the target voltage (v_target) according to the relationship t=−

RCln(v_target/v_current) and wherein at least some of the predetermined cell discharge times are different.

2. The vehicle of claim 1 wherein the target voltage is a minimum of the initial voltages.

3. The vehicle of claim 1 wherein the at least one controller is further configured to subsequently charge the cells.