Charging device which monitors charging by detecting a temperature of the battery and which includes compensation for increases or decreases in ambient temperature

• US 6,278,260 B1
• Filed: 12/08/1999
• Issued: 08/21/2001
• Est. Priority Date: 12/08/1999
• Status: Expired due to Fees

• Current Assignee: Tai-Her Yang
• Original Assignee: Tai-Her Yang
• Inventors: Yang, Tai-Her
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/456,512
• Time in Patent Office: 622 Days
• Field of Search: 320/150
• US Class Current: 320/150
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A charging device monitors charging by detecting temperature, and includes environmental temperature differential compensation capabilities so that a charging control circuit is simultaneously supplied with the output of an ambient temperature detector, on the one hand, and the output of a detector of the temperature of a rechargeable cell in a state of being charged, on the other hand, so that when the ambient temperature decreases, the battery temperature threshold or testing point for determining a charge saturation status of the rechargeable cell is reduced accordingly, while when the ambient temperature increases, the corresponding battery temperature threshold or testing point will be increased correspondingly, thereby increasing the precision and reliability of the charge saturation test results.

Claims

1. A charging device arranged to monitor a charging state of a rechargeable battery by detecting a temperature of the battery, comparing the detected battery temperature with a threshold, and determining whether the battery has reached a state of charge saturation based on a comparison of the detected battery temperature with the threshold, comprising:

a battery temperature detector arranged to detect a temperature of the battery;

an ambient temperature detector arranged to detect an ambient temperature; and

a control circuit arranged to determine whether said battery has reached a state of charge saturation by comparing a temperature detected by the battery temperature detector with a threshold,

wherein an input of said control circuit is connected to an output of said ambient temperature detector, said control circuit being arranged to adjust said threshold based on the output of said ambient temperature detector such that when said ambient temperature increases, said threshold is increased, and such that when said ambient temperature decreases, said threshold is reduced.

2. A charging device as claimed in claim 1, further comprising a master control element connected in series between the battery and a charging current source, and wherein said control circuit is arranged to at least reduce said charging current when said threshold is reached.

3. A charging device as claimed in claim 1, wherein said battery temperature detector and ambient temperature detector are negative temperature resistance coefficient elements.

4. A charging device as claimed in claim 1, wherein said battery temperature detector and ambient temperature detector both are positive temperature resistance coefficient elements.

5. A charging device as claimed in claim 1, wherein said battery temperature detector is a negative temperature resistance coefficient element and said ambient temperature detector is a positive temperature resistance coefficient element.

6. A charging device as claimed in claim 1, wherein said battery temperature detector is a positive temperature resistance coefficient element and said ambient temperature detector is a negative temperature resistance coefficient element.

7. A charging device as claimed in claim 1, wherein said battery temperature detector is a normally closed electromechanical thermo-sensitive switching element and said ambient temperature detector includes a preheating resistor connected in series with a negative temperature resistance coefficient sensor, and in parallel with a power source to thereby adjust said threshold by changing a switching point of said thermo-sensitive switching element in an inversely proportional manner relative to the ambient temperature.

8. A charging device as claimed in claim 1, wherein said battery temperature detector is a normally open electromechanical thermo-sensitive switching element and said ambient temperature detector includes a preheating resistor connected in series with a negative temperature resistance coefficient sensor, and in parallel with a power source to thereby adjust said threshold by changing a switching point of said thermo-sensitive switching element in an inversely proportional manner relative to the ambient temperature.

9. A charging device as claimed in claim 1, wherein said battery temperature detector is a normally closed electromechanical thermo-sensitive switching element and said ambient temperature detector includes a preheating resistor connected in parallel with a positive temperature resistance coefficient sensor and further in parallel with a power source to thereby adjust said threshold by changing a switching point of said thermo-sensitive switching element in an inversely proportional manner relative to the ambient temperature.

10. A charging circuit as claimed in claim 9, further comprising a regulatory resistor connected in series between said power source and said parallel-connected preheating resistor and positive temperature resistance coefficient sensor.

11. A charging device as claimed in claim 1, wherein said battery temperature detector is a normally open electromechanical thermo-sensitive switching element arranged to switch at a specific temperature and said ambient temperature detector includes a preheating resistor connected in parallel with a positive temperature resistance coefficient sensor and further in parallel with a power source to thereby adjust said threshold by changing said specific temperature at which said thermo-sensitive switching element is arranged to switch in such a manner that said specific temperature is increased when said ambient temperature decreases, and said specific temperature is decreased when said ambient temperature increases.

12. A charging device as claimed in claim 11, further comprising a regulatory resistor connected in series between said power source and said parallel-connected preheating resistor and positive temperature resistance coefficient sensor.

13. A charging device as claimed in claim 11, wherein said battery temperature detector is a thermo-sensitive switching element connected in series with the battery to thereby control a charging current supplied to said battery.