Battery pack

• US 8,384,353 B2
• Filed: 04/19/2010
• Issued: 02/26/2013
• Est. Priority Date: 04/24/2009
• Status: Expired due to Fees

• Current Assignee: Panasonic Electric Works Power Tool Company Limited
• Original Assignee: Panasonic Electric Works Power Tool Company Limited
• Inventors: Miyazaki, Hiroshi, Sakaue, Masaaki
• Primary Examiner(s): DIAO, M BAYE
• Application Number:
  US12/662,462
• Publication Number:
  US 20100270973A1
• Time in Patent Office: 1,044 Days
• Field of Search: 320/120, 320/134, 320/136
• US Class Current: 320/120
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H02J 7/00036 Charger exchanging data with battery
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery pack which is detachably connected to a charger and charged by connecting thereto, includes a battery assembly including a plurality of secondary batteries serially connected; a pair of power terminals connected to a negative and a positive electrode of the battery assembly, respectively; a control circuit adapted to individually detect voltages across respective secondary batteries and output a charge control signal to the charger when the detected voltages exceed a predetermined value; a signal terminal adapted to output the charge control signal to the charger; and a temperature measurement element for detecting a temperature of the battery assembly. Further, the control circuit changes the predetermined value to be compared with the detected voltages based on the detected temperature of the temperature measurement element.

Claims

1. A battery pack which is detachably connected to a charger and charged by connecting thereto, comprising:

a battery assembly including a plurality of secondary batteries serially connected;

a pair of power terminals connected to a negative and a positive electrode of the battery assembly, respectively;

a control circuit adapted to individually detect voltages across respective secondary batteries and output a charge control signal to the charger when the detected voltages exceed a predetermined value;

a signal terminal adapted to output the charge control signal to the charger; and

a temperature measurement element for detecting a temperature of the battery assembly,

wherein the control circuit is configured to select, as the predetermined value, one of two or more values based on the detected temperature of the temperature measurement element.

2. The battery pack of claim 1, wherein the control circuit includes a first detection circuit adapted to individually detect voltages across respective secondary batteries and output a charge control signal when the detected voltages exceed a first predetermined value;

a second detection circuit adapted to individually detect voltages across respective secondary batteries and output a charge control signal when the detected voltages exceed a second predetermined value which is different from the first predetermined value; and

a selection circuit adapted to selectively output the charge control signal outputted from the first detection circuit and the charge control signal outputted from the second detection circuit to the charger depending on the detected temperature of the temperature measurement element.

3. The battery pack of claim 2, wherein the temperature measurement element includes a thermistor having a resistance changing depending on temperature, and is connected between a pair of temperature measurement signal terminals coupled to the charger;

one of the temperature measurement signal terminals is connected to ground for signal, ground of the control circuit is connected to ground of the battery assembly, and the ground for signal and the ground of the battery assembly are separately provided; and

the control circuit further includes an insulation circuit and the temperature measurement signal terminals are connected to the selection circuit via the insulation circuit.

4. The battery pack of claim 3, wherein the insulation circuit includes a resistor bridge circuit having the temperature measurement element, and a comparator for comparing a reference value with a voltage corresponding to the detected temperature of the temperature measurement element.

5. The battery pack of claim 3, wherein the control circuit further includes a plurality of diodes, each having an anode connected to the ground for signal and a cathode connected to one of the temperature measurement signal terminals.

6. The battery pack of claim 4, wherein the control circuit further includes a plurality of diodes, each having an anode connected to the ground for signal and a cathode connected to one of the temperature measurement signal terminals.