Battery charger and method to recall last charge state

Details Battery charger and method to recall last charge state Battery charger and method to recall last charge state

2001-07-18

2002-09-24

Tso, Edward H. (Department: 2838)

Electricity: battery or capacitor charging or discharging

Means to identify cell or battery type

C320S133000

Reexamination Certificate

active

06456037

ABSTRACT:

BACKGROUND
1. Technical Field
This invention relates generally to battery chargers, and more specifically to smart chargers having capabilities to identify batteries and to charge them accordingly.
2. Background Art
Portable devices routinely depend upon batteries as a power source. To reduce battery replacement costs, rechargeable batteries have found wide utility in powering contemporary consumer and business products. For example, both nickel- and lithium-based batteries may be repeatedly used to energize computers, radios, pagers, phones and other such devices.
Manufacturers have developed many devices for charging batteries. Some of these chargers are in the form of desk-top stands, where the user can leave the stand plugged in all the time and charge the battery simply by placing the device in the stand. The stand thus serves a dual function: first it acts as a charger, and second it acts as a mechanical holder for the electronic device. A problem with chargers of this type is that they can overcharge batteries, thereby compromising battery performance and cycle life.
For example, imagine a person with a two-way radio sitting in a desk-stand charger. If the person wants to transmit a message, he takes the radio out of the stand, presses the “talk” button and sends his message. Once he has finished transmitting, a process that may take a matter of seconds, the person will typically reinsert the radio back into the stand. After all, if the person doesn't want the radio lying about haphazardly on the desk, the stand provides a tidy and stable holder for the radio.
The problem with this “take out; use for a short time; reinsert” method is that nickel-based batteries can be overcharged. Typical nickel-based battery chargers have at least two modes: rapid charge and trickle charge. When a dead battery is inserted into a charger, the charger wants to charge the battery as fast as possible, so the charger blasts the battery with a high current. This is known as rapid charge. Once the battery “fills up”, the charger detects a rapid rise in temperature—due to cell impedance increasing—and the charger switches to a very low current. The low current, which is just enough to keep the battery topped off, is known as “trickle” charge.
When a person takes a fully charged battery out of the charger and uses it for a brief period of time and reinserts it into the charger, the charger has no way of knowing that the battery is nearly fully charged. As a result, the charger blasts the battery in rapid charge mode until it detects a temperature rise. As there is a time delay with the temperature rise, the battery gets ever so slightly over charged. When the process is repeated numerous times, battery reliability is compromised.
Prior art solutions have attempted to solve this problem. For example, U.S. Pat. No. 5,175,211, issued to Brotto, teaches a means of identifying a battery via a resistor identifier or a microprocessor. The problem with the prior art is that it merely identifies the battery type, e.g. “This is a lithium battery”; or “This is a 1 Amp-hour, prismatic, Sony, cell.” The prior art solutions do not identify the status of charge to avoid overcharging.
There is thus a need for an improved battery identification system.


REFERENCES:
patent: 5150031 (1992-09-01), James et al.
patent: 5568037 (1996-10-01), Massaroni et al.
patent: 5633573 (1997-05-01), van Phuoc et al.
patent: 5912544 (1999-06-01), Miyakawa et al.
patent: 6175211 (2001-01-01), Brotto
patent: 6252380 (2001-06-01), Koenck

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