Rechargeable battery pack

• US 6,448,743 B2
• Filed: 06/28/2001
• Issued: 09/10/2002
• Est. Priority Date: 06/29/2000
• Status: Active Grant

• Current Assignee: Toshiba Battery Co., Ltd. (Toshiba Corporation)
• Original Assignee: Toshiba Battery Co., Ltd. (Toshiba Corporation)
• Inventors: Ishitsuka, Kiyoshi, Sano, Yoshinao, Shiojima, Nobuo
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/892,443
• Publication Number:
  US 20020000790A1
• Time in Patent Office: 439 Days
• Field of Search: 320/162, 324/429, 324/430-435, 340/636, 702/63
• US Class Current: 320/162
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A rechargeable battery pack has a battery voltage detector, a full charge detecting circuit detecting a full charge state, a switch interposed in a charge current circuit that opens the charge current circuit when detecting a fall charge state, a memory for storing a closed circuit voltage immediately before the charge current circuit is opened, an internal resistance detection circuit for finding a value corresponding to an internal resistance of the rechargeable battery cell from an open circuit voltage and the closed circuit voltage stored in the memory after the charge current circuit is opened, and a lifetime indicator to predict lifetime. This enables accurate determination of the lifetime of the rechargeable battery cell under stable conditions without wastefully consuming the charging capacity.

Claims

1. A rechargeable battery pack comprising:

at least one rechargeable battery cell,

a battery voltage detecting means for detecting a terminal voltage of said rechargeable battery cell,

a fall charge detecting means for detecting a full charge state of said rechargeable battery cell when a predetermined parameter reaches a value indicating achievement of the fall charge state of said rechargeable battery cell while said rechargeable battery cell is charged,

a switch device interposed in a charge current circuit of said rechargeable battery cell and turned off to open said charge current circuit when said full charge detecting means detects a full charge state,

a memory for storing a closed circuit voltage Von of said rechargeable battery cell detected by said battery voltage detecting means immediately before said charge current circuit is opened,

an internal resistance detecting means for finding a value corresponding to an internal resistance Rin of said rechargeable battery cell from an open circuit voltage Voff of said rechargeable battery cell detected by said battery voltage detecting means and the closed circuit voltage Von stored in said memory after said charge current circuit is opened, and

a lifetime indicating means for predicting the lifetime of said rechargeable battery cell in accordance with the value corresponding to the internal resistance of said rechargeable battery cell and outputting information on the lifetime.

3. A rechargeable battery pack as set forth in claim 1 or 2, wherein:

said internal resistance detecting means includes timer means for measuring a time elapsed from the time of detecting the full charge state of the rechargeable battery cell;

said internal resistance detecting means finds an open circuit voltage Voff of said rechargeable battery cell when a predetermined elapsed time from the time of detecting the full charge state of the rechargeable battery cell is measured by said timer means.

4. A rechargeable battery pack as set forth in claim 1 or 2, further comprising:

means for prohibiting the internal resistance detecting means from calculating the internal resistance of the rechargeable battery cell when a discharge current of said rechargeable battery cell is detected by said current detecting means.

5. A rechargeable battery pack as set forth in claim 1 or 2, further comprising:

battery temperature detecting means for detecting a temperature of said rechargeable battery cell; and

correcting means for correcting the value corresponding to the internal resistance of the rechargeable battery cell found by said internal resistance detecting means in accordance with the battery temperature detected by said battery temperature detecting means.

6. A rechargeable battery pack as set forth in claim 1 or 2, further comprising:

switch control means for operating said switch device to repeatedly close and open a charge current circuit for said rechargeable battery cell,

wherein said internal resistance detecting means detects the states of the rechargeable battery cell immediately before the charge current circuit is opened and after the charge current circuit is opened to evaluate the lifetime of the rechargeable battery cell.

7. A rechargeable battery pack as set forth in claim 1 or 2, wherein the rechargeable battery cell includes:

a nickel-metal hydride (Ni-MH) type cell.

8. A rechargeable battery pack as set forth in claim 1 or 2, wherein:

said full charge detecting means includes means for detecting the full charge state when a battery voltage, serving as the predetermined parameter of the rechargeable battery cell, assumes its pak voltage.

9. A rechargeable battery pack as set forth in claim 1 or 2, wherein:

said full charge detecting means includes means for detecting the full charge state when a battery voltage, serving as the predetermined parameter of the rechargeable battery cell, falls by a predetermined voltage from its peak voltage after the peak voltage is reached.

10. A rechargeable battery pack as set forth in claim 1 or 2, wherein:

said full charge detecting means includes means for detecting the full charge state based on a rate of rise of temperature of the rechargeable battery cell, the rate of rise of temperature serving as the predetermined parameter.

2. A rechargeable battery pack comprising:

at least one rechargeable battery cell,

a battery voltage detecting means for detecting a terminal voltage of said rechargeable battery cell,

a current detecting means for detecting a charge/discharge current with respect to said rechargeable battery cell,

a full charge detecting means for detecting a full charge state of said rechargeable battery cell when a predetermined parameter reaches a value indicating achievement of the full charge state of said rechargeable battery cell while said rechargeable battery cell is charged,

a switch device interposed in a charge current circuit of said rechargeable battery cell and turned off to open said charge current circuit when said fall charge detecting means detects a fall charge state,

a memory for storing a closed circuit voltage Von of said rechargeable battery cell detected by said battery voltage detecting means and a battery charge current Ion detected by said current detecting means immediately before said charge current circuit is opened,

an internal resistance detecting means for finding a value corresponding to an internal resistance Rin of said rechargeable battery cell from an open circuit voltage Voff of said rechargeable battery cell detected by said battery voltage detecting means and a current Ioff detected by said current detecting means after said charge current circuit is opened and the closed circuit voltage Von and battery charge current Ion stored in said memory, and

a lifetime indicating means for predicting the lifetime of said rechargeable battery cell in accordance with the value corresponding to the internal resistance of said rechargeable battery cell and outputting information on the lifetime.