WO1998014975A1 - Charging system for an appliance with rechargeable batteries which are charged when the appliance is placed in a stand - Google Patents

Charging system for an appliance with rechargeable batteries which are charged when the appliance is placed in a stand Download PDF

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Publication number
WO1998014975A1
WO1998014975A1 PCT/IB1997/000830 IB9700830W WO9814975A1 WO 1998014975 A1 WO1998014975 A1 WO 1998014975A1 IB 9700830 W IB9700830 W IB 9700830W WO 9814975 A1 WO9814975 A1 WO 9814975A1
Authority
WO
WIPO (PCT)
Prior art keywords
charging
battery
rechargeable battery
appliance
stand
Prior art date
Application number
PCT/IB1997/000830
Other languages
French (fr)
Inventor
Adrianus Petrus Johannes Maria Jongenelis
Robert Eduard Fransiscus Einerhand
Original Assignee
Philips Electronics N.V.
Philips Norden Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Electronics N.V., Philips Norden Ab filed Critical Philips Electronics N.V.
Publication of WO1998014975A1 publication Critical patent/WO1998014975A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • Charging system for an appliance with rechargeable batteries which are charged when the appliance is placed in a stand
  • the invention relates to a charging system comprising: an electrical appliance with a rechargeable battery incorporated therein; and a stand for supplying charging current to the rechargeable battery when the electrical appliance has been placed in the stand.
  • a charging system is known from European Patent Application EP 0
  • the rechargeable appliance is an electric toothbrush.
  • the charging unit for charging the battery being accommodated in the stand.
  • Rechargeable appliances other than electric toothbrushes such as electric shavers, screwdrivers, drills, hand-held vacuum cleaners, hand-held mixers, electric knives, portable telephone sets and the like are also placed back into their stands.
  • a common feature of these appliances is that after use they are generally placed back into a stand, base, wall mount or the like, which accommodates the charging unit which charges the battery of the appliance when the appliance is placed back.
  • the appliance and the charging unit comprise corresponding electrical contacts.
  • the stand and the appliance having windings which form a transformer when the appliance is placed in the stand.
  • the voltage induced in the winding of the appliance is rectified to enable the battery to be charged.
  • stand is to be understood to mean also a base, a wall mount or the like. Since the appliance should always be ready for use the charging unit is generally connected continuously to the mains voltage, as a result of which the rechargeable battery is charged continuously each time that the appliance is placed back in the stand.
  • This continuous charging is permissible if the continuous charging current is not too large but is it does not contribute to a long life of the rechargeable battery. A consequence of this is that the battery often breaks down before the life of the appliance has ended and a completely new appliance is to be purchased.
  • the charging system of the type defined in the opening paragraph is characterized in that the charging system further comprises: means for measuring the degree of charging of the rechargeable battery; and means to prevent charging current from being supplied to the rechargeable battery when the measured degree of charging exceeds a threshold value smaller than the maximum degree of charging.
  • the threshold value can be, for example, 20 % of the maximum energy available in the battery, but a favourable value is that for which the threshold value corresponds to an energy content in the rechargeable battery which is adequate for a subsequent operating cycle of the appliance.
  • a further embodiment of the charging system in accordance with the invention is characterized in that the charging system further comprises: means for stopping the supply of charging current to the rechargeable battery when the measured degree of charging is equal to the maximum degree of charging.
  • the charging system further comprises: means for stopping the supply of charging current to the rechargeable battery when the measured degree of charging is equal to the maximum degree of charging.
  • the memory effect can be reduced by means of an embodiment which is characterized in that the charging system further comprises: means for discharging the battery prior to the supply of charging current.
  • Means for measuring the degree of charging are known per se from, for example, European Patent Specification EP 0 248 461 and European Patent Application EP 0 425 044, which disclose a battery management system with charge indication for an electric shaver with rechargeable batteries.
  • a simple alternative for determining the degree of charging is a battery voltage measurement. Charging is effected only when the voltage is below a given threshold voltage.
  • Figure 1 shows an electric toothbrush with a charging system in accordance with the invention
  • FIG. 2 shows an electrical circuit diagram of an embodiment of a charging system in accordance with the invention.
  • FIG 1 shows an electric toothbrush with a charging system in accordance with the invention.
  • the toothbrush comprises a brush section 2 to be handled by a user, which brush section is placed into a stand 4 after use.
  • the stand 4 accommodates a charging current unit 6, which is connected to the mains via a mains cord 8, and a simple battery management system 10.
  • the brush section 2 accommodates an electric motor 12 which sets a brush 14 in motion, electronic drive means 16 for controlling the motor 12, an on/off switch 18 for turning the motor 12 on and off, a rechargeable battery 20, and contacts 22 which establish an electrical connection between the stand 4 and the brush section 2 when the brush section 2 is placed in the stand 4.
  • the battery management system 10 monitors the degree of charging of the rechargeable battery 20 and ensures that the charging current unit 6 only supplies charging current to the battery 20 if the degree of charging of the battery 20 is smaller than a predetermined value, for example smaller than 20 % of the maximum capacity.
  • the manner in which the battery management system measures and controls the degree of charging can be based on methods which are known per se. With some of these methods that are known per se it is necessary to accommodate electronic elements in the brush section 2 instead of or in addition to the relevant electronic elements in the stand 4.
  • European Patent Specification EP 0 248 461 and European Patent Application EP 0 425 044 give examples of the implementation of battery management systems based on the duty time of the battery and on the amount of charge drained from the battery.
  • the present example uses a comparatively simple method based on battery voltage measurement, the electrical circuit diagram of which is shown in Figure 2.
  • the stand 4 accommodates a transformer 30 having its primary winding 32 connected to the mains voltage via the mains cord 8.
  • the voltage of the secondary winding 34 is rectified by means of a rectifier 36 and is smoothed by means of a capacitor 38.
  • the smoothed voltage U powers a power supply unit 40, which generates a constant current or a constant voltage for charging the battery 20 via the contacts 22 and an electronic switch 42.
  • the power supply unit can be a DC-DC converter, a special IC for battery charging, a circuit for supplying a constant current, a circuit for supplying a constant voltage etc.
  • the electronic switch 42 can be a relay or a transistor.
  • the electronic switch is controlled by a logic unit 44, which determines whether or not the power supply unit 40 is allowed to supply charging current to the battery 20.
  • the logic unit 44 receives a signal from a first comparator 46, which compares the battery voltage with a first reference voltage U R1 which corresponds to the battery voltage at, for example, 20 % residual capacity of the battery 20.
  • a first comparator 46 which compares the battery voltage with a first reference voltage U R1 which corresponds to the battery voltage at, for example, 20 % residual capacity of the battery 20.
  • Charging can be effected with a comparatively small current. In that case charging may proceed until the brush section is removed from the stand for a subsequent operating cycle. However, particularly if it is desired to charge the battery 20 rapidly with a comparatively large charging current, charging should be stopped in due time so as to preclude overcharging and breakdown of the battery 20. Charging can be stopped in various manners, for example on the basis of a measurement of the battery temperature. In the present example a voltage measurement has been selected, a second comparator comparing the battery voltage with a second reference voltage U R2 , which corresponds to the battery voltage at 100 % capacity. When the battery 20 is full the logic unit 44 turns off the charging current by means of the electronic switch 42.
  • the power supply unit 40, the electronic switch 42 and, if desired, also the logic unit 44 and the comparators 46 and 48 can be united in one integrated circuit or IC.
  • a second electronic switch 50 has been provided, by means of which a discharge resistor 52 can be arranged across the terminals 22 under command of the logic unit 44.
  • a discharge resistor 52 can be arranged across the terminals 22 under command of the logic unit 44.

Abstract

A charging system for an electrical appliance, for example an electric toothbrush (2) with a rechargeable battery (20) incorporated therein. After use the appliance is placed in a stand (4) which accommodates a charger (6) which recharges the rechargeable battery (20) via electrical contacts (22). The charging system comprises means (10) for measuring the degree of charging of the rechargeable battery (20). In order to extend the life of the battery (20) the battery (20) is charged only if the degree of charging is smaller than a threshold value.

Description

Charging system for an appliance with rechargeable batteries which are charged when the appliance is placed in a stand.
The invention relates to a charging system comprising: an electrical appliance with a rechargeable battery incorporated therein; and a stand for supplying charging current to the rechargeable battery when the electrical appliance has been placed in the stand. Such a charging system is known from European Patent Application EP 0
634 151 , in which the rechargeable appliance is an electric toothbrush. After use rechargeable electric toothbrushes are generally put back into their stands by the user, the charging unit for charging the battery being accommodated in the stand. Rechargeable appliances other than electric toothbrushes, such as electric shavers, screwdrivers, drills, hand-held vacuum cleaners, hand-held mixers, electric knives, portable telephone sets and the like are also placed back into their stands. A common feature of these appliances is that after use they are generally placed back into a stand, base, wall mount or the like, which accommodates the charging unit which charges the battery of the appliance when the appliance is placed back. For this purpose, the appliance and the charging unit comprise corresponding electrical contacts. However, there are also inductive chargers, the stand and the appliance having windings which form a transformer when the appliance is placed in the stand. The voltage induced in the winding of the appliance is rectified to enable the battery to be charged. Hereinafter, "stand" is to be understood to mean also a base, a wall mount or the like. Since the appliance should always be ready for use the charging unit is generally connected continuously to the mains voltage, as a result of which the rechargeable battery is charged continuously each time that the appliance is placed back in the stand. This continuous charging is permissible if the continuous charging current is not too large but is it does not contribute to a long life of the rechargeable battery. A consequence of this is that the battery often breaks down before the life of the appliance has ended and a completely new appliance is to be purchased. Furthermore, it is known from nickel-cadmium (NiCd) and nickel-metal hydroxide (NiMH) batteries that repeated partial discharging and subsequent full recharging is detrimental to the life of the battery, which effect is referred to as the memory effect. It is an object of the invention to provide a charging system which extends the battery life and which reduces the likelihood of needless premature replacement of the appliance. To this end, in accordance with the invention, the charging system of the type defined in the opening paragraph is characterized in that the charging system further comprises: means for measuring the degree of charging of the rechargeable battery; and means to prevent charging current from being supplied to the rechargeable battery when the measured degree of charging exceeds a threshold value smaller than the maximum degree of charging. This ensures that the battery is not charged each time that it is put back into the stand. The threshold value can be, for example, 20 % of the maximum energy available in the battery, but a favourable value is that for which the threshold value corresponds to an energy content in the rechargeable battery which is adequate for a subsequent operating cycle of the appliance.
A further embodiment of the charging system in accordance with the invention is characterized in that the charging system further comprises: means for stopping the supply of charging current to the rechargeable battery when the measured degree of charging is equal to the maximum degree of charging. Thus, it is prevented that, once the system has decided to charge the battery, the battery is charged unnecessarily long or is overcharged. This makes it possible to use a quick-charging system, as a result of which the appliance is sooner ready for use in the case of a battery which has been discharged to a considerable extent, as in the case that the appliance has been used for a longer than normal or average time.
The memory effect can be reduced by means of an embodiment which is characterized in that the charging system further comprises: means for discharging the battery prior to the supply of charging current.
Means for measuring the degree of charging are known per se from, for example, European Patent Specification EP 0 248 461 and European Patent Application EP 0 425 044, which disclose a battery management system with charge indication for an electric shaver with rechargeable batteries. However, a simple alternative for determining the degree of charging is a battery voltage measurement. Charging is effected only when the voltage is below a given threshold voltage.
These and other aspects of the invention will be described and elucidated with reference to the accompanying drawings, in which
Figure 1 shows an electric toothbrush with a charging system in accordance with the invention; and
Figure 2 shows an electrical circuit diagram of an embodiment of a charging system in accordance with the invention.
In these Figures like elements and parts bear the same reference symbols. Figure 1 shows an electric toothbrush with a charging system in accordance with the invention. The toothbrush comprises a brush section 2 to be handled by a user, which brush section is placed into a stand 4 after use. The stand 4 accommodates a charging current unit 6, which is connected to the mains via a mains cord 8, and a simple battery management system 10. The brush section 2 accommodates an electric motor 12 which sets a brush 14 in motion, electronic drive means 16 for controlling the motor 12, an on/off switch 18 for turning the motor 12 on and off, a rechargeable battery 20, and contacts 22 which establish an electrical connection between the stand 4 and the brush section 2 when the brush section 2 is placed in the stand 4. The battery management system 10 monitors the degree of charging of the rechargeable battery 20 and ensures that the charging current unit 6 only supplies charging current to the battery 20 if the degree of charging of the battery 20 is smaller than a predetermined value, for example smaller than 20 % of the maximum capacity. The manner in which the battery management system measures and controls the degree of charging can be based on methods which are known per se. With some of these methods that are known per se it is necessary to accommodate electronic elements in the brush section 2 instead of or in addition to the relevant electronic elements in the stand 4. European Patent Specification EP 0 248 461 and European Patent Application EP 0 425 044 give examples of the implementation of battery management systems based on the duty time of the battery and on the amount of charge drained from the battery.
The present example uses a comparatively simple method based on battery voltage measurement, the electrical circuit diagram of which is shown in Figure 2. The stand 4 accommodates a transformer 30 having its primary winding 32 connected to the mains voltage via the mains cord 8. The voltage of the secondary winding 34 is rectified by means of a rectifier 36 and is smoothed by means of a capacitor 38. The smoothed voltage U; powers a power supply unit 40, which generates a constant current or a constant voltage for charging the battery 20 via the contacts 22 and an electronic switch 42. The power supply unit can be a DC-DC converter, a special IC for battery charging, a circuit for supplying a constant current, a circuit for supplying a constant voltage etc. The electronic switch 42 can be a relay or a transistor. The electronic switch is controlled by a logic unit 44, which determines whether or not the power supply unit 40 is allowed to supply charging current to the battery 20. For this purpose, the logic unit 44 receives a signal from a first comparator 46, which compares the battery voltage with a first reference voltage UR1 which corresponds to the battery voltage at, for example, 20 % residual capacity of the battery 20. When the brush section is put back into the stand, which can be detected, for example, on the basis of a variation of the voltage across or a variation of the current through the contacts 22, the logic unit 44 examines the output signal of the first comparator 46 and determines whether the electronic switch 42 should be closed in order to charge the battery.
Charging can be effected with a comparatively small current. In that case charging may proceed until the brush section is removed from the stand for a subsequent operating cycle. However, particularly if it is desired to charge the battery 20 rapidly with a comparatively large charging current, charging should be stopped in due time so as to preclude overcharging and breakdown of the battery 20. Charging can be stopped in various manners, for example on the basis of a measurement of the battery temperature. In the present example a voltage measurement has been selected, a second comparator comparing the battery voltage with a second reference voltage UR2, which corresponds to the battery voltage at 100 % capacity. When the battery 20 is full the logic unit 44 turns off the charging current by means of the electronic switch 42. The power supply unit 40, the electronic switch 42 and, if desired, also the logic unit 44 and the comparators 46 and 48 can be united in one integrated circuit or IC. Moreover, in order to reduce the memory effect of the battery 20, a second electronic switch 50 has been provided, by means of which a discharge resistor 52 can be arranged across the terminals 22 under command of the logic unit 44. Thus, it is possible to first discharge the battery 20 completely upon each or several decisions to recharge the battery 20. It will be obvious that the principles disclosed herein can also be applied to other electrical appliances with rechargeable batteries which after use are generally placed back in a stand, wall mount, base or other device, such as electric shavers, screwdrivers, drills, hand-held vacuum cleaners, hand-held mixers, electric knives, portable telephone sets and the like.

Claims

CLAIMS:
1. A charging system comprising: an electrical appliance (2) with a rechargeable battery (20) incorporated therein; and a stand (4) for supplying charging current to the rechargeable battery (20) when the electrical appliance (2) has been placed in the stand (4), characterized in that the charging system further composes means (46, 44) for measuring the degree of charging of the rechargeable battery (20); and means (42, 44) to prevent charging current from being supplied to the rechargeable battery (20) when the measured degree of charging exceeds a threshold value smaller than the maximum degree of charging
2. A charging system as claimed in Claim 1 , characteπzed in that the charging system further comprises means (48, 44, 42) for stopping the supply of charging current to the rechargeable battery (20) when the measured degree of charging is equal to the maximum degree of charging.
3. A charging system as claimed in Claim 1 or 2, characteπzed in that the threshold value corresponds to an energy content of the rechargeable battery (20) which is adequate for a subsequent operating cycle of the appliance (2)
4 A charging system as claimed in Claim 1 , 2 or 3, characteπzed in that the charging system further comprises means (44, 50, 52) tor discharging the battery (20) pπor to the supply of charging cuπent
5 An electric toothbrush comprising a brush section (2) including a movable brush (14), a motor (12) for driving the brush (14), and a rechargeable battery (20) for supplying current to the motor (12), and a stand (4) for supplying charging current to the rechargeable battery (20) when the brush section (2) has been placed in the stand, characteπzed in that the charging system further comprises means (46, 44) for measuring the degree of charging of the rechargeable battery (20); and means (42, 44) to prevent charging cuπent from being supplied to the rechargeable battery (20) when the measured degree of charging exceeds a threshold value smaller than the maximum degree of charging
PCT/IB1997/000830 1996-09-30 1997-07-04 Charging system for an appliance with rechargeable batteries which are charged when the appliance is placed in a stand WO1998014975A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP96202719 1996-09-30
EP96202719.9 1996-09-30

Publications (1)

Publication Number Publication Date
WO1998014975A1 true WO1998014975A1 (en) 1998-04-09

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB1997/000830 WO1998014975A1 (en) 1996-09-30 1997-07-04 Charging system for an appliance with rechargeable batteries which are charged when the appliance is placed in a stand

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5115182A (en) * 1990-04-23 1992-05-19 Motorola, Inc. Battery charging controller for a battery powered device and method for using the same
EP0669693A1 (en) * 1994-02-28 1995-08-30 Black & Decker Inc. Battery recharging system with state of charge detection to prevent overcharging

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5115182A (en) * 1990-04-23 1992-05-19 Motorola, Inc. Battery charging controller for a battery powered device and method for using the same
EP0669693A1 (en) * 1994-02-28 1995-08-30 Black & Decker Inc. Battery recharging system with state of charge detection to prevent overcharging

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