Apparatus and methods for determining appropriate timing for recharging rechargeable batteries

• US 6,577,104 B2
• Filed: 04/15/2002
• Issued: 06/10/2003
• Est. Priority Date: 04/17/2001
• Status: Expired due to Term

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Sakakibara, Kazuyuki
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/123,508
• Publication Number:
  US 20020149346A1
• Time in Patent Office: 421 Days
• Field of Search: 320/106, 320/110, 320/128, 320/132, 320/134, 320/136, 320/133, 320/155, 320/157, 320/158, 320/159, 320/135
• US Class Current: 320/132
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

When rechargeable batteries have been discharged to a selected voltage reference level, LED 29 (and/or buzzer BZ) and controller 32 may warn the operator that the rechargable batteries should be recharged. Controller 32 may change the selected reference voltage level based upon use history information concerning the rechargeable batteries. The use history information may, e.g., be stored in EEPROM 52 of battery pack 40. Thus, the rechargeable batteries can be discharged to different voltage levels before the operator is warned that the rechargeable batteries should be recharged. In addition or in the alternative, switch 36 may be disposed between the rechargeable batteries and a motor (M). Controller 32 may open switch 36 when the detected voltage of the rechargeable batteries drops below the selected reference voltage level (or a derivative of the selected reference voltage level) in order to interrupt the flow of current to the motor (M). Thus, the rechargeable batteries can be prevented from being over-discharged and from developing memory effects, thereby prolonging the usable life of the rechargeable batteries.

Claims

1. An apparatus comprising:

a voltage detector arranged and constructed to detect the voltage level of at least one rechargeable battery, and

a controller arranged and constructed to (a) select a reference voltage level from a plurality of reference voltage levels stored in memory based upon use history of the rechargeable batteries stored in memory, (b) compare the detected battery voltage level to the selected reference voltage level, and (c) indicate that the at least one rechargeable battery is due for recharging when the detected battery voltage level becomes equal to or less than the selected reference voltage level.

2. An apparatus as in claim 1, wherein the controller is further arranged and constructed to select a first reference voltage level when the use history does not satisfy a predetermined condition and to select a second reference voltage level when the use history satisfies the predetermined condition, and wherein the second reference voltage level is lower than the first reference voltage level.

3. An apparatus as in claim 2, further comprising at least one means for warning an operator that the rechargeable batteries are due for recharging when the detected battery voltage becomes equal to or less than the selected reference voltage level.

4. An apparatus as in claim 3, further comprising means for shutting off electric current supplied by the rechargeable batteries to a load when the detected battery voltage becomes equal to or less than (a) the selected reference voltage level or (b) the selected reference voltage level minus a small voltage (EV. Δ

V).

5. An apparatus as in claim 1, further comprising means for shutting off electric current supplied by the rechargeable batteries to a load when the detected battery voltage becomes equal to or less than (a) the selected reference voltage level or (b) the selected reference voltage level minus a small voltage (EV. Δ

V).

6. An apparatus as in claim 1, further comprising:

at least one means for warning an operator that the rechargeable batteries are due for recharging when the detected voltage of the rechargeable batteries becomes equal to or less than the selected reference voltage level, and

means for shutting off electric current supplied by the recharagble batteries to a load when the detected voltage of the rechargeable batteries becomes equal to or less than the selected reference voltage level minus a small voltage (EV. Δ

V), wherein the warning means first warns the operator when the detected voltage of the rechargeable batteries falls below the selected reference voltage and, if the operator does not discontinue use of the rechargeable batteries before the detected voltage of the rechargeable batteries falls below the selected reference voltage level minus a small voltage (EV. Δ

V), the shutting off means automatically stops the supply of electric current from the rechargeable batteries to the load.

7. An apparatus as in claim 5, further comprising the at least one rechargeable battery, wherein the load comprises a power tool motor driven by the rechargeable batteries.

8. An apparatus as in claim 1, further comprising the at least one rechargeable battery and a power tool motor driven by the rechargeable batteries.

21. An apparatus as in claim 1, further comprising means for releasably attaching to a battery pack comprising the at least one rechargeable battery and means for releasably attaching to a power tool comprising a motor driven by the at least one rechargeable battery.

9. A method for determining an appropriate timing for recharging at least one rechargeable battery, comprising:

selecting a reference voltage level from a plurality of reference voltage levels based upon use history of the at least one rechargeable battery, wherein the use history and the plurality of reference voltage levels are stored in a semiconductor memory,

detecting the voltage level of the at least one, rechargeable battery,

comparing the detected battery voltage level to the selected reference voltage level, and

indicating to an operator that the at least one rechargeable battery is due for recharging when the detected battery voltage level becomes equal to or less than the selected reference voltage level.

10. A method as in claim 9, further comprising shutting off electric current supplied by the rechargeable batteries when the detected battery voltage becomes equal to or less than the selected reference voltage level minus a small voltage (EV. Δ

V).

11. A method as in claim 10, further comprising supplying current from the at least one rechargeable battery to a motor of a power tool while detecting the voltage level of the at least one rechargeable battery.

12. A method as in claim 9, further comprising supplying current from the at least one rechargeable battery to a motor of a power tool which detecting the voltage level of the at least one rechargeable battery.

13. An apparatus for determining an appropriate timing for recharging at least one rechargeable battery, comprising:

means for detecting the voltage level of the at least one rechargeable battery,

means for storing a plurality of reference voltage levels and for storing use history of the at least one rechargeable battery,

means for selecting a reference voltage level from the plurality of stored reference voltage levels based upon the stored use history for the at least one rechargeable battery,

means for comparing the detected battery voltage level to the selected reference voltage level, and

means for indicating to an operator that the at least one rechargeable battery is due for recharging when the detected battery voltage level becomes equal to or less than the selected reference voltage level.

14. An apparatus as in claim 13, further comprising means for shutting off electric current supplied by the rechargeable batteries when the detected battery voltage becomes equal to or less than the selected reference voltage level minus a small voltage (EV.Δ

V).

15. An apparatus as in claim 14, further comprising means for supplying current from the at least one rechargeable battery to a motor of power tool while detecting the voltage level of the at least one rechargeable battery.

16. An apparatus as in claim 13, further comprising means for supplying current from the at least one rechargeable battery to a motor of a power tool while detecting the voltage level of the at least one rechargeable battery.

17. An apparatus as in claim 13, wherein the indicating means comprise a light.

18. An apparatus as in claim 13, wherein the indicating means comprises a buzzer.

19. An apparatus as in claim 13, further comprising the at least one rechargeable battery, wherein the load comprises a power tool motor driven by the rechargeable batteries.

20. An apparatus as in claim 13, further comprising means for releasably attaching to a battery pack comprising the at least one rechargeable battery and means for releasably attaching to a power tool comprising a motor driven by the at least one rechargeable battery.