Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
1998-12-09
2001-01-23
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S134000
Reexamination Certificate
active
06177780
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a battery charger. More particularly, the invention relates to a modular battery charger system with charging control distributed among various modules. Still more particularly, the invention relates to a modular charger system with improved reliability and employing an improved method for determining a fully charged battery.
2. Background of the Invention
Although rechargeable batteries and battery rechargers have been available for years, significant room for improvement remains in this technology. Some rechargeable batteries are used in non-benign, outdoor environments. For example, land-based seismic survey equipment typically employs rechargeable batteries to power the data acquisition units used to acquire seismic data. These batteries, like all rechargeable batteries, must be recharged periodically. Normally, the batteries are removed from the equipment and connected to rechargers which are transported to the site being seismically surveyed. For some surveys it may be preferable to leave the recharging equipment in the field rather than transporting it to the field each time the batteries need charging.
As such, the rechargers are operated in an outdoor environment which often is harsh to the electronics comprising the recharger. The environment may include conditions such as high humidity, high or low temperature, rain, snow, or sleet. Such environmental conditions increase the likelihood of a failure in the charger. Field-based battery chargers typically are constructed to minimize the risk of the internal components becoming ruined from moisture and also to reduce damage to the unit occasioned by falling tree limbs, mishandling by field personnel and other factors. Although being able to easily maintain the recharger is important, conventional chargers are constructed more for durability than maintainability. That is, servicing such chargers usually is difficult to perform in the field. Thus, when a conventional charger fails, a technician is sent into the field to examine and, if possible, repair the unit. Often, however, the technician is forced to return the unit to a well-equipped, indoor service facility to make the repair, a procedure which is time consuming and costly.
Some field-based battery chargers are capable of charging more than one battery at a time. Such chargers usually have multiple charging circuits, each circuit capable of charging a single battery. Typically, if just one of the charging circuits in such a charger fails, the entire charger, including the remaining fully functional charging circuits, may have to be transported to a service facility to repair or replace the one malfunctioning circuit. Thus, because of one malfunctioning charging circuit, the entire charging capability of the charger is lost until the repair is completed. Accordingly, it would be desirable have a battery charger that, is highly reliable, and also can be repaired without losing the full charging capability of the unit while the failure is being corrected.
The desire for increased reliability also applies to battery chargers that are used indoors in a more benign environment where the possibility of a malfunction still exists. In many indoor applications, battery chargers may be used in time critical events such as related to the use of medical equipment in a hospital in which battery and battery charger “down time” should be minimized.
Another aspect of reliable battery charging involves determining when a battery has been fully charged. Determining the “end of charge” condition prevents a battery from being over-charged, a condition that can damage certain types of rechargeable batteries. Many conventional end of charge determinations are based on measuring the voltage of the battery and determining when the voltage meets or exceeds a predetermined threshold. Often, such voltage-based end of charge protocols are inaccurate because of a particular battery's chemistry. Such inaccuracies may cause a battery to be under-charged (i.e., not be fully charged) or be over-charged to a certain extent. Thus, a more accurate, reliable method for determining the end of charge condition is needed.
Accordingly, it would be desirable to have a battery charger that provides greater reliability and maintainability than with conventional chargers and can more precisely charge a battery to full capacity. Despite the advantages that such a charger would offer, to date no such charger has been introduced.
BRIEF SUMMARY OF THE INVENTION
The deficiencies of the prior art described above are solved in large part by a battery charger system that provides increased reliability over conventional chargers. The charging system includes one or more charging modules coupled to a central controller module. Each charging module operates independently of, and is unaffected by, other charging modules. In this manner, reliability of the overall charging system is increased because a failure of one charging module does not affect the charging capability of other charging modules.
Electrical power for charging the batteries and driving the electronics internal to the charging and controller modules preferably is provided by a 24 VDC power supply. Each charging module is cable of charging one or more batteries and includes control logic that separately controls the charging current provided to each battery. Each charging module is capable of charging the associated batteries using a pre-programmed, selectable charging protocol. The control logic included in any each charging module provides a “first level of intelligence” for charging batteries. The first level of intelligence generally selects various stages of charging and discontinues charging when the battery is fully charged.
The controller module provides a “second level of intelligence” that generally operates in conjunction with the first level of intelligence provided by the discrete charging modules. The second level of intelligence provided by the controller module enables and disables charging to an individual battery by asserting an inhibit signal to the charging module associated with the targeted battery. Disabling battery charging may be desired as a result of detecting a fully charged battery or detecting fault conditions such as over voltage, over current, out of range temperature, or leakage current. Disabling battery charging also may be desired as a result of detecting faulty batteries by monitoring rate of voltage, current and temperature changes within the charging battery. The charging modules advantageously are capable of charging batteries even without control from the second level of intelligence. Thus, reliability also is increased by being able to continue battery charging even if the controller module fails or is removed from the battery charging system.
Other factors contribute to the increased reliability of the preferred battery charging system. For example, the present battery charging system does not require a pair of sense lines connecting the battery terminals to the charging module as is typical for conventional battery chargers. Sense lines of conventional chargers permit those chargers to determine the actual voltage of the battery without the voltage drop associated with battery cables. The charging modules of the preferred embodiment include a resistor which develops a voltage indicative of the current through the battery and that voltage is used by the control logic in each charger module to compensate for battery cable voltage drop during charging.
The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following disclosure.
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patent: 4918368 (1990-04-01), Baker et al.
patent: 5013992 (1991-05-01), Eavenson et al.
patent: 5157320 (1992-10-01), Kuriloff
patent: 5198743 (1993-03-01), McClure et al.
patent: 5319298 (1994-06-01), Wanzong et al.
patent: 5422558 (1995-06-01), Stewart
patent: 5459671 (1995-10-01), Duley
pa
Lafont Don
Roy James
Conley & Rose & Tayon P.C.
Harris Jonathan M.
Toatley Jr. Gregory J
Veritas DGC Inc.
Wong Peter S.
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