Conditioning of a rechargeable battery

• US 6,747,439 B2
• Filed: 12/12/2002
• Issued: 06/08/2004
• Est. Priority Date: 05/28/2002
• Status: Expired due to Fees

• Current Assignee: Braun GmbH (The Procter & Gamble Company)
• Original Assignee: Braun GmbH (The Procter & Gamble Company)
• Inventors: Franke, Michael
• Primary Examiner(s): Tibbits, Pia
• Application Number:
  US10/317,325
• Publication Number:
  US 20030222622A1
• Time in Patent Office: 544 Days
• Field of Search: 320/133, 320/131, 320/132, 320/135, 320/149, 320/155, 320/6.21, 324/428
• US Class Current: 320/133
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/0071 with a programmable schedule

Abstract

Methods and devices for the conditioning of a rechargeable battery. The methods include providing a fully charged battery and discharging that battery to a voltage threshold value. The time required to discharge the rechargeable battery to the voltage threshold value is measured and then compared to a reference value. If the discharge time is less than the reference value, the battery is then further discharged. The methods can be applied to rechargeable batteries used in consumer products such as electric shaver and electric toothbrushes. The devices include a rechargeable battery, a second device that detects whether the device is connected to an external energy sources, and an electronic circuit. The electronic circuit discharges the battery by way of a load only if the device is connected to an external energy source. The devices can include appliances such as an electronic shaver or an electronic toothbrush.

Claims

1. A method of conditioning a rechargeable battery, the method comprising:

providing a fully charged rechargeable battery;

measuring a discharge time for which the voltage of the battery takes to decrease to a voltage threshold value;

comparing the discharge time to a reference value, and if the discharge time is less than the reference value, shorting the battery through a discharge load to further discharge the battery.

2. The method of claim 1, further comprising:

measuring a current flow during discharge;

from the measured current flow and the measured discharge time, determining a charge quantity;

comparing the determined charge quantity with the charge quantity of a reference value; and

if the battery voltage drops to the voltage threshold value before the charge quantity corresponding to the reference value is released, shorting the battery through the discharge load to further discharge the battery.

3. The method of claim 1 or 2, wherein shorting the battery through a discharge load fully discharges the battery.

4. The method of claim 2, wherein the current flow is measured while also measuring the discharge time.

5. The method of claim 1 or 2, further comprising:

measuring a first time interval which has passed since the battery voltage last dropped to the voltage threshold value;

determining whether the first time interval exceeds a maximum reference time; and

if the first time interval exceeds the maximum reference time, shorting the battery through the discharge load to discharge the battery until the battery voltage drops to the voltage threshold value.

6. The method of claim 1 or 2, further comprising after shorting the rechargeable battery, recharging the rechargeable battery.

7. The method of claim 6, further comprising

measuring again a discharge time for which the voltage of the battery takes to decrease to the voltage threshold value;

comparing again the discharge time to the reference value;

if the discharge time is again less than the reference value, indicating, on a display, that the discharge time is less than the reference value.

8. The method of claim 7, further comprising

measuring again a current flow during discharge;

from the measured current flow and the measured discharge time, determining again the charge quantity;

comparing again the determined charge quantity with the charge quantity of the reference value;

if the battery voltage drops to the voltage threshold value again before the charge quantity corresponding to the reference value is released, indicating, on a display, that the charge quantity is less than the reference value.

9. The method of claim 7, wherein the current flow is measured while also measuring the discharge time.

10. The method of claim 1 or 2, further comprising:

measuring a second time interval since a latest replacement or charging of the battery;

comparing the second time interval to a minimum reference time; and

if the second time interval exceeds the minimum reference time, and if during the second time interval the battery voltage dropped to the voltage threshold value due solely to self-discharge of the battery;

then activating a display to indicate that the rechargeable battery is aged or needs to be replaced.

11. The method of claim 1 or 2, further comprising changing the voltage threshold value to correspond with a change in temperature.

12. An electrical appliance comprising:

a discharge load;

a rechargeable battery for powering the electrical appliance connected through a switch to the discharge load for powering the discharge load;

a connector for connecting the appliance to an external source of electrical energy; and

an electronic circuit that measures a discharge time for which the voltage of the battery takes to decrease to a voltage threshold value, compares the discharge time to a reference value, and if the discharge time is less than the reference value, shorts the battery through the discharge load to further discharge the battery only while the appliance is connected to the external energy source.

13. The appliance of claim 12, wherein the electronic circuit:

measures a current flow during discharge;

from the measured current flow during the measured discharge time, determines a charge quantity;

compares the determined charge quantity with the charge quantity of a reference value; and

if the battery voltage drops to the voltage threshold value before the charge quantity corresponding to the reference value is released, shorts the battery through the discharge load to further discharge the battery.

14. The appliance of claim 12 or 13, wherein shorting the battery through the discharge load fully discharges the battery.

15. The appliance of claim 13, wherein the current flow is measured while also measuring the discharge time.

16. The appliance of claim 12 or 13, wherein the electronic circuit:

measures a first time interval which has passed since the battery voltage last dropped to the voltage threshold value;

determines whether the first time interval exceeds a maximum reference time; and

if the first time interval exceeds the maximum reference time, shorts the battery through the discharge load to discharge the battery until the battery voltage drops to the voltage threshold value.

17. The appliance of claim 12 or 13, wherein the electronic circuit after shorting the rechargeable battery recharges the battery.

18. The appliance of claim 12 or 13, wherein the discharge load is a resistor disposed within the appliance.

19. The appliance of claim 12 or 13, wherein the appliance is an electric shaver.

20. The appliance of claim 12 or 13, wherein the appliance is an electric toothbrush.