Charging/discharging control method for secondary battery

• US 6,573,687 B2
• Filed: 05/15/2001
• Issued: 06/03/2003
• Est. Priority Date: 11/24/1998
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Murakami, Yusai, Kimura, Tadao
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/858,353
• Publication Number:
  US 20010033150A1
• Time in Patent Office: 749 Days
• Field of Search: 320/118, 320/119, 320/132, 320/149, 324/427, 324/432, 324/433, 324/426
• US Class Current: 320/132
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors

Abstract

A battery pack is formed by serially connecting a plurality of cells, that are individually constructed as rechargeable batteries. Charging and discharging of this battery pack are controlled such that, the proportion of discharge current with respect to the charge current equals to a value obtained by multiplying the charge current by a charging efficiency corresponding to a target SOC value.

Claims

1. A method for maintaining a predetermined state of charge of a battery pack, including equalizing states of charge of individual cells of the battery pack, comprising:

determining a charging efficiency of the cells at said predetermined state of charge; and

repetitively charging and discharging said battery pack wherein;

said charging includes delivering a predetermined amount of charge to the battery which is less than that necessary to charge the battery pack to a 100% state of charge; and

said discharging includes draining a discharge amount of charge equal to said predetermined amount multiplied by said charging efficiency of the cells at said predetermined state of charge.

2. The method of claim 1 wherein:

said charging includes applying a charge current over a charge time period to deliver said predetermined amount of charge; and

said discharging includes draining a discharge current over a discharge period of time equal to said charge time period, wherein said discharge current is equal to said charge current multiplied by said charging efficiency.

3. The method of claim 2 where said discharge and charge currents are maintained at a substantially constant value during said discharging and said charging.

4. The method of claim 1 wherein:

said charging includes applying a charge current profile over a charge time period to deliver said predetermined amount of charge; and

said discharging includes draining a discharge current profile, equal to said charge current profile, over a discharge period of time to discharge a discharge amount of charge equal to said predetermined amount of charge multiplied by said charging efficiency.