Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Reexamination Certificate
2000-09-08
2001-09-11
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
C320S124000
Reexamination Certificate
active
06288521
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to charging mechanisms for batteries and in particular to recharging batteries which must be substantially discharged before recharging.
2. Description of the Prior Art
A growing number of “cordless” or “mobile” electronic devices rely on rechargeable batteries rather than disposable batteries, including wireless telephones, laptops, personal digital assistants (PDAs), cordless telephones, etc. The devices typically utilize battery power when not connected to another power source, and recharge the battery when connected to an external power source through a charging cradle, power adapter, or the like.
In order to maximize useful lifetime, nickel-cadmium (NiCad) rechargeable batteries must be substantially discharged before being recharged. Although generally less expensive than “memory-free” rechargeable batteries such as nickel metal hydride (NiMH) or lithium ion (Li-Ion) batteries, the need for discharge prior to recharging has resulted in NiCad batteries finding less commercial acceptance than might be expected. A probable cause of this unpopularity is the hassle of trying to remember whether a battery has been discharged, or waiting until the battery has been discharged, before recharging.
Various charging schemes have been proposed for NiCad rechargeable batteries, each of which have proven less than satisfactory. For example, “flash” discharge mechanisms designed to quickly discharge a battery to an acceptable level before recharging have reduced the wait before a battery may be recharged, but can be only somewhat less harmful to battery life than recharging before complete discharge. Battery life is best when the battery is discharged utilizing a slow, controlled drain through a load.
It would be desirable, therefore, to provide a power management system for rechargeable batteries which intelligently controls discharge and recharging to extend battery life.
SUMMARY OF THE INVENTION
An electronic device battery pack for a battery requiring cycling to prolong lifetime is divided into at least two parallel cells for which the charging state is automatically maintained. When external power is available and one or more cells is substantially discharged, the substantially discharged cell(s) are selected one at a time to be fully drained and recharged. A partially discharged but not substantially discharged cell will be left in that state until use of the electronic device has substantially discharged the cell. Once a cell has been recharged, the next substantially discharged cell is drained and recharged, and so on until all cells are fully charged. If the charging of a cell is interrupted by removal of the external power, another cell is utilized to provide power to the electronic device and recharging is resumed once the external power is restored. A device kept in a charging cradle except when being utilized may thus be used and returned to the charging cradle without adversely impacting battery life.
REFERENCES:
patent: 5656915 (1997-08-01), Eaves
patent: 5666006 (1997-09-01), Townsley et al.
patent: 5739596 (1998-04-01), Takizawa et al.
patent: 5867007 (1999-02-01), Kim
patent: 5959368 (1999-10-01), Kubo et al.
patent: 6060864 (2000-05-01), Ito et al.
Galanthay Theodore E.
Jorgenson Lisa K.
STMicroelectronics Inc.
Tibbits Pia
Venglarik Daniel E.
LandOfFree
Intelligent power management for rechargeable batteries does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Intelligent power management for rechargeable batteries, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Intelligent power management for rechargeable batteries will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2504061