Method and apparatus for equalizing secondary cells

• US 20060214636A1
• Filed: 12/22/2005
• Published: 09/28/2006
• Est. Priority Date: 03/04/2005
• Status: Abandoned Application

• Current Assignee: Yazaki Corporation
• Original Assignee: Yazaki Corporation
• Inventors: Yamamoto, Kouichi, Arai, Youichi
• Application Number:
  US11/313,656
• Publication Number:
  US 20060214636A1
• Time in Patent Office: Days
• US Class Current: 320/116
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

The present invention is to provide an equalizing method and an apparatus thereof for preventing unit cells from being over charged and discharged. After an ignition switch is turned off, CPU checks a voltage of a main battery and judges whether the main battery is in a state of equilibrium or not. When the main battery is in the state of equilibrium, the CPU controls a first and second switch groups to equalize voltages of unit cells included in the main battery by repeating a charge transfer from a maximum voltage cell to a minimum voltage cell for a predetermined period of time.

Claims

1. A method of equalizing a voltage of each unit cell of serially connected secondary unit cells, comprising:

the step of equalizing the voltage of the each unit cell when the unit cell is in a state of equilibrium.

2. An apparatus for equalizing a voltage of each unit cell of serially connected secondary unit cells, comprising:

a CPU being installed;

a judging process program processed in the CPU for judging whether the each unit cell is in a state of equilibrium or not; and

an equalizing process program processed in the CPU for starting equalization of the voltage of the each unit cell when the each unit cell is in the state of equilibrium.

3. The apparatus as claimed in claim 2, wherein said equalizing process program starts the equalization of the voltage of the each unit cell when an ignition switch of a vehicle is turned off and the each unit cell is in the state of equilibrium.

4. The apparatus as claimed in claim 2, wherein said judging process program judges that the each unit cell is in the state of equilibrium when a current flow of the unit cell is not detected for a prescribed period of time.

5. The apparatus as claimed in claim 2, wherein said judging process program judges that the each unit cell is in the state of equilibrium when the current flow of the unit cell is not detected and the voltage becomes constant.

6. The apparatus as claimed in claim 3, further comprising a voltage detector for detecting the voltage of the each unit cell, wherein said voltage detector inputs the voltage of the each unit cell to the CPU and the equalizing process program in the CPU repeats a charge transfer operation from a unit cell having the maximum voltage to a unit cell having the minimum voltage through a capacitor for a predetermined period of time.

7. The apparatus as claimed in claim 6, wherein said predetermined period of time is a time required for the unit cells to reach a constant value in voltage.