Battery charger and charging method

• US 6,075,347 A
• Filed: 02/26/1999
• Issued: 06/13/2000
• Est. Priority Date: 02/28/1998
• Status: Expired due to Term

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Sakakibara, Kazuyuki
• Primary Examiner(s): Berhane, Adolf Deneke
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/258,140
• Time in Patent Office: 473 Days
• Field of Search: 320/150-154, 320/160, 429/61, 324/431, 324/426, 324/441, 340/636, 340/640, 340/643, 20/150
• US Class Current: 320/150
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A battery charger and a charging method capable of charging a battery for a short period of time while suppressing battery temperature from rising. The current temperature of the battery is detected (in step S12) and a temperature rise is calculated from the detected temperature (in step S14). An allowable current map is then retrieved from the detected temperature and the obtained temperature rise, an allowable current with which the battery can be charged while suppressing battery temperature from rising is obtained (in step S16) and the battery is charged with the allowable current (in step S20). Since the allowable current which the battery can be charged with, while suppressing battery temperature from rising is retrieved using the map which the allowable current is mapped, based on battery temperature and battery temperature rise, and charging current is controlled, it is possible to charge the battery for a short period of time while suppressing battery temperature from rising.

Claims

1. A battery charger comprising:

a memory for storing a map for mapping an allowable value of current, with which a battery can be charged while suppressing battery temperature from rising, based on a battery temperature and a battery temperature rise, said map having the allowable current value set low when the battery temperature is high and set low when the temperature rise is large;

a temperature detection device for detecting a current temperature of the battery;

a temperature rise output device for obtaining the temperature rise from the temperature detected by said temperature detection device;

an allowable current retrieval device for retrieving the map of said memory device from the temperature detected by said temperature detection device and the temperature rise outputted from said temperature rise output device, and for obtaining said allowable value;

a charging device for charging the battery with the allowable current retrieved by said allowable current retrieval device;

a charging completion determination device for determining that charging is completed based on whether the temperature detected by said temperature detection device and the temperature rise outputted from said temperature rise output device belong to a region indicating a final charging stage on the map of said memory device with a high frequency; and

a charging completion device for completing charging based on the determination of said charging completion determination device when charging is completed.

2. A charging method comprising steps of:

detecting a current temperature of a battery;

obtaining a temperature rise from said detected temperature;

retrieving an allowable current map based on battery temperature and battery temperature rise, from said detected temperature and said obtained temperature rise, and obtaining an allowable value of current with which the battery can be charged while suppressing the battery temperature from rising;

charging the battery with said retrieved allowable current;

determining that charging is completed based on whether the outputted temperature rise is relatively large and whether relatively low allowable current is outputted from said map with a high frequency; and

completing charging based on the determination that charging is completed.