Electricity: battery or capacitor charging or discharging – Battery or cell discharging – Regulated discharging
Reexamination Certificate
2000-03-14
2002-05-21
Toatley, Jr., Gregory J. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
Regulated discharging
C320S162000, C320S150000
Reexamination Certificate
active
06392387
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to battery packs and battery charging systems.
BACKGROUND AND OVERVIEW OF THE INVENTION
Battery packs consist of a plurality of electrochemical devices. Electrochemical devices comprise such devices as rechargeable batteries, fuel cells, double layer capacitors, and a hybrid battery containing fuel cell electrode and electrochemical supercapacitors. Battery cells are electrochemical devices that store energy in chemical form. A rechargeable battery cell is capable of storing electrical charge in the form of a reversible chemical reaction. When the battery cell is subsequently placed across a load, this reaction reverses from the direction in the storage mode, thereby producing electrical energy for use by the load. Rechargeable battery packs, also known as secondary batteries, are widely used as a power source for many devices. The number and type of electrochemical devices comprising the battery pack determines the power rating of a battery pack. A battery pack may consist of rechargeable battery cells in series, in parallel, or in series and parallel. To obtain a battery pack consisting of rechargeable battery cells which has a higher voltage than a single cell's voltage, typically a plurality of cells are placed in series, while to obtain a battery pack that has a higher capacity than a single cell's storage capacity, typically a plurality of cells are placed in parallel.
Those skilled in the art understand battery cell life and performance can be enhanced with battery cell conditioning. Battery cell conditioning occurs when the battery cell is discharged in a predetermined sequence in relationship to the recharging of the battery cell. Prior art further teaches us the benefits of pulse charging and discharging. U.S. Pat. No. 5,633,574 entitled “Pulse charge Battery Charger”, issued to Sage on May 27, 1997 provides enhanced battery conditioning capability with pulse charging and discharging, and is hereby incorporated by reference. In order to accomplish the discharge pulse for battery pack conditioning, current from the battery pack must flow in the reverse direction, that is, from the battery pack to a load included in the battery charger. However, not all battery packs are capable of allowing a discharge pulse through all of their terminals.
Battery packs may include short circuit battery terminal protection preventing a conditioning reverse current flow from occurring through these terminals. Unprotected battery terminals may themselves come in contact with foreign objects, which can cause a battery pack to short circuit, spark, or cause the terminals to overheat. To deal with this problem, battery packs may include two sets of terminals or connectors, one unprotected operatively accessible by the battery powered device and one set of terminals accessible to an external power source for battery charging. This external set of charging terminals may be short circuit protected or unprotected. Alternatively, battery packs with two sets of terminals can be located within the battery powered device, with one set of terminals operatively coupled to or positioned adjacent to a set of terminals located in the housing of the device, which are themselves accessible to an external power source for battery charging.
The present start of the art for passively protecting battery pack terminals from an externally induced short circuit uses a conventional blocking diode operatively coupled to the battery terminals. However, the conventional blocking diode conducts current in only one direction, thereby preventing the discharging of the battery pack through these terminals. This type of battery pack protection requires a battery charging system using a discharging means for conditioning of battery packs to be operatively coupled to a set of unprotected battery pack terminals or connectors, therefore requiring the removal of the battery pack with protected external terminals from the battery powered device to expose the unprotected terminals or connectors and then, once removed from the device, further requiring the user to operatively couple the battery pack to the battery charging system. These charging systems require the user to take the time to execute this operation, and take more time to replace the battery pack on the battery powered device once battery charging and conditioning is completed, thereby adding to the total labor time and costs associated with using battery powered devices and in the case of emergency personnel such as firefighters, adding to their overall emergency response time as well.
Prior art has addressed the lack of discharge capability of the conventional blocking diode passively protected battery pack by adding an active means of “turning on” and “turning off” an electronic device included in the charge path of the battery pack. “U.S. Pat. No. 5,710,505” shows us a battery pack with short circuit protection which allows both charging and discharging. “U.S. Pat. No. 5,710,505” uses a Triac device in the charge path of a battery pack and operationally requires a battery pack with a minimum of three terminals. The Triac device, when actively “turned on”, allows the conduction of current through the device. However, a limitation of a Triac device is that once the device is in an “on state”, that is, conductive, the current through the device must be interrupted, or drop below a minimum holding current, to restore the non-conductive “off state” condition, thereby restoring the short circuit protection. Therefore, unless the current in “U.S. Pat. No. 5,710,505” is reduced to the minimum level or completely interrupted, the reverse current non-conductive battery short circuit protection will not be restored. This same operational limitation which applies to a triac device likewise applies to a Thyristor. Field Effect Transistors (FETs) and Metal Oxide FETs (MOSFETs) devices also must be “turned on” to conduct current, but then must be actively “turned off” to restore the non-conductive state, thereby restoring the battery pack short circuit protection.
In addition to devices such as Triacs and Thyristors, current flow can also be controlled using voltage clamping devices, which include but are not limited to, Zeners, Transient Voltage Suppressors (TVS), and Metal Oxide Varistors (MOV). Voltage clamping devices have a reverse voltage breakdown threshold; that is, allowing the conduction of a reverse current flow without restriction through the voltage clamping device, given enough reverse voltage is applied, then automatically restoring to a non-conducting mode when the voltage drops below the breakdown threshold. Depending on operating conditions, the breakdown threshold of the voltage clamping device may be due to an avalanche type junction breakdown or a tunneling type junction breakdown or a combination of both. This voltage breakdown threshold is a well-defined reproducible operating characteristic of the device. The classic voltage-current interrelationship diagram for voltage clamping devices is depicted in
FIG. 4
of the accompanying drawings.
Each voltage clamping device will have an optimum operating voltage range and will exhibit predictable operating variations such as reaction time, variation in reverse current leakage, and variations in device failure mode and device failure frequency. The useful life of the voltage clamping device in the battery pack is dependent on the correct voltage clamping device selection for the specific battery pack application. Voltage clamping devices are further characterized by specifying the maximum clamping voltage at the maximum reverse current rating. Silicon voltage clamping devices incorporating a larger junction cross section are also known as Transient Voltage Suppressors (TVS) and will survive a large number of reverse current draws, given the appropriate operational environment.
The overall useful life, that is, survival capability under a particular load for a specific time period, of the voltage clamping device can be maximized with the
Fuhr Jay A.
Sage George E.
Sage Electronics and Technology, Inc.
Toatley , Jr. Gregory J.
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