Indirect thermal sensing system for a battery charger

• US 6,020,721 A
• Filed: 12/31/1998
• Issued: 02/01/2000
• Est. Priority Date: 05/03/1996
• Status: Expired due to Term

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Brotto, Daniele C.
• Primary Examiner(s): TIBBITS, PIA FLORENCE
• Assistant Examiner(s): Shin, K.
• Application Number:
  US09/224,546
• Time in Patent Office: 397 Days
• Field of Search: 320/150, 320/151, 320/152, 324/441, 429/62
• US Class Current: 320/150
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A battery charger including a battery temperature monitoring device. The battery temperature monitoring device includes a first thermistor bonded to one of the terminals of the battery charger to provide a temperature signal of the temperature of the terminal, and a second thermistor positioned within the battery charger to provide a temperature signal of the ambient temperature. The temperature signals from both the first and second thermistors are applied to a temperature monitoring circuit that compares the temperature signals to a known discharge rate of an RC circuit. A microprocessor receives output signals from the temperature monitoring circuit and, using an algorithm, determines the actual temperature of the battery.

Claims

1. A temperature monitoring device for determining the temperature of a battery pack being charged in a charging device, said charging device including a charging terminal, said monitoring device comprising:

an ambient temperature sensor positioned to sense ambient temperature within the battery charger and providing a temperature signal of the sensed ambient temperature;

a terminal temperature sensor positioned to sense the temperature of the charging terminal and providing a temperature signal indicative of the temperature of the terminal;

a temperature monitoring circuit responsive to the temperature signals from the ambient temperature sensor and the terminal temperature sensor, said temperature monitoring circuit providing output signals indicative of the temperature signals; and

controller means responsive to the output signals from the monitoring circuit for determining the temperature of the battery pack based on the temperature signals in accordance with the equation;

space="preserve" listing-type="equation">T.sub.BATT =C.sub.1 T.sub.1 +C.sub.2 T.sub.0 +C.sub.3 T.sub.A +C.sub.4

where,

T_BATT is the temperature of the battery pack;

T₀ is the temperature of the charging terminal before the battery pack is inserted into the charging device;

T₁ is the temperature of the charging terminal after the battery pack is inserted into the charging device; and

T_A is the ambient temperature within the battery charger.

2. A battery charger for charging a battery, said battery charger comprising:

a terminal for providing electrical energy to the battery;

first sensing means for sensing the temperature of the terminal;

second sensing means for sensing ambient temperature in the vicinity of the battery charger;

controller means for controlling the battery charger in response to the temperature of the battery which is determined by the controller means in accordance with the equation;

space="preserve" listing-type="equation">T.sub.BATT =C.sub.1 T.sub.1 +C.sub.2 T.sub.0 +C.sub.3 T.sub.A +C.sub.4

where,

T_BATT is the temperature of the battery;

T₀ is the temperature of the charging terminal before the battery is inserted into the charging device;

T₁ is the temperature of the charging terminal after the battery is inserted into the charging device; and

T_A is the ambient temperature within the battery charger.