Patent Application
20050118497
The invention relates to the field of battery evaluation. More specifically, it relates to methods and assemblies for determining the state of charge of one or more batteries without disturbing the surrounding environment of the batteries.
Battery-operated electrical devices are very common, and in many situations it is desirable to determine the state of charge of the batteries before they are used to provide power to a device. It is also desirable that this determination be made as quickly and easily as possible. The need to assess the state of charge can be especially crucial in situations where a battery has been idle for an extended time period but must then reliably supply power at any given moment. In such situations recharging or replacing defective batteries alone may be too time consuming or even impossible, and replacing an entire electronic or electrical assembly is the only feasible remedy, once the battery state of charge is quickly determined. A quick and easy method of battery testing would be beneficial in such areas as emergency equipment, military equipment, and avionics.
As one example, flashlights and batteries to power them are often kept in storage for use during a power outage or other emergency. A supply of charged batteries must be immediately available at all times. An easy way to monitor the state of charge of such stored batteries is clearly essential.
Another example is an alarm system that must be put into service immediately upon installation. It would be highly desirable for full battery capacity to be available to provide full functionality of the alarm system without waiting for the batteries to become charged.
As another example, quality control of battery-operated devices would be facilitated by a convenient battery evaluation. A charged battery may gradually become discharged while on an assembly line, after sitting for a long time in a warehouse, or after being delivered to a customer. A simple way to check the state of charge of the battery would benefit the manufacturer and purchaser alike.
U.S. Pat. No. 3,454,873, granted to Abrahams discloses a very simple battery test device using a small light bulb as indicator. Although simple and convenient, this device provides only a crude, qualitative indication of the state of charge, not sufficient for the applications described above.
A battery tester is often included in the packaging of AA or 9-volt batteries. One attaches the positive and negative battery terminals to the tester and a colored display indicates whether the battery is fully charged, partially charged, or only minimally charged. These battery testers are typically rather complex multilayer flat structures incorporating a thermochromic or electrochromic material, one which changes color in response to heat or electric fields, respectively. Such testers are disclosed in U.S. Pat. Nos. 5,223,003; 5,389,458; and 5,418,085; U.S. Patent Application Publication US/0049522; and EP Application Publication 0 495 636 A2.
Another class of battery testers makes use of a separate electrochemical or electrolytic cell, as disclosed in U.S. Pat. Nos. 5,627,472 and 5,596,278. However, the need for an extra cell makes such testers relatively complex and costly.
U.S. Pat. No. 6,291,096 B1 discloses a relatively simple tester that continuously displays the state of charge of a battery, with no action required by the user. While offering convenience, this device must continuously draw a small current from the battery, which could discharge the battery over a prolonged idle period.
There is thus a need for a simple, quick, and inexpensive method and apparatus for assessing the state of charge of batteries prior to use. For greatest convenience, one should be able to assess the batteries without disturbing them or removing them from their packaging or from a device in which they are installed.
The invention comprises a method and assembly for quickly and easily evaluating the state of charge of at least one battery without disturbing the batteries. In one embodiment, the batteries are physically installed in a battery-operated device, but the battery terminals are electrically insulated from contact areas of the device by insulating material between the terminals and the contact areas. The purpose of this insulating is to minimize loss of battery charge before the device is put into operation. At the same time, positive and negative battery terminals are each in electrical contact with an electrical conductor, and these conductors extend outward from the battery-operated device. This enables a user to bring the battery terminals into electrical contact with a measuring device, such as a voltmeter, and thereby determine the state of charge of the battery or batteries. If the state of charge is determined to be acceptable, the insulating material may then be removed, bringing the battery terminals into electrical contact with the contact areas of the battery-powered device, thereby activating the device. If the state of charge is found to be unacceptable, the battery may be recharged or replaced or the entire assembly of battery and battery-operated device may be replaced and the state of charge measured again.
In another embodiment, the batteries, with or without a battery-operated device, are either partially or fully enclosed in such a way that direct physical contact with the actual terminals of the batteries is not possible. Conductors, connected to battery terminals at one end, extend to the outside of the enclosure, thereby allowing one to determine the state of charge of the batteries by attaching a measuring device to the conductors outside the enclosure. An example of this embodiment is batteries enclosed in a package, with the conductors extending to the outside of the package.
Once the state of charge is determined, the battery-operated device may be activated by removing the conductors 13 and insulator 12 by pulling in the direction of the solid arrow. Once this is done the battery terminals 20 will be in electrical contact with the device contact areas 22 and power from the battery will be conveyed to the battery-powered device through the wires 15 and 16 connected to the device contact areas 22.
Alternatively, the conductors 13 could be sandwiched between two layers of insulting material. In this case the layer indicated by 12 in
In one embodiment the insulating material 12 and the conductors 13 are integrated into a single unit in the form of a flat flexible ribbon. The insulating material 12 must withstand the voltage of the battery 11 without breakdown and without allowing leakage currents to flow. It should also have a slippery quality, allowing it to be easily removed by sliding. It must also have sufficient mechanical integrity so as not to be punctured, tom, or otherwise penetrated by the battery terminals 20 or device contact areas 22. Suitable materials for the insulator 12 include, but are not limited to, bonded spun polymeric material such as those known by the trademark TYVEK®; polymeric paper, pressboard, nonwoven materials, and film materials, such as those known by the trademarks TEFLON®, KAPTON®, MYLAR®, KYNAR®, and NOMEX®; or paper coated with a wax or a resin.
Also in this embodiment, the conductors 13 are in the form of thin film-like stripes of conducting material, providing connections between the battery terminals and the measuring device. Preferably, these stripes may be fabricated on the insulating material by a process such as, but not limited to, painting, spraying, printing, or silk-screen printing. Suitable materials for the conducting stripes include, but are not limited to, carbon ink, thin carbon films, and conductive epoxies.
In another embodiment the resistance of the stripes 13 is relatively high and the measuring device 24 is a high-impedance voltmeter which measures the open-circuit voltage of the battery 11. An advantage of using such high-impedance conductors is that very little current is drawn from the battery during the test. A further advantage is that the high resistance of the stripes 13 will limit the current drawn from the battery 11, thereby preventing damage to the battery in the event that the conductors 13 are bridged or “shorted” by highly conducting material. Alternatively, at least one of the conductors 13 could be in series with a resistance high enough to prevent damage to the battery by limiting the current in the event the conductors are bridged. Alternatively, at least one of the conductors 13 could be in series with a fuse, which is designed to open in the event the conductors are bridged, thereby protecting the battery.
In other embodiments, the measuring device 24 could be an ammeter for measuring current, a thermochromic, electrochromic, or electrophoretic device, or an electrochemical cell or an electrolytic cell.
In this embodiment, the conducting stripes 13 are connected to the battery terminals at one end (not shown) and the stripes 13 extend to and terminate on the outside of the package 30. The state of charge of the battery may be determined by placing the probes of a measuring device on the two test point targets 14. The battery terminals are electrically isolated from each other and from other conductors by the insulating material 12.
If the state of charge is found unacceptable the package may be returned to the vendor unopened, thereby avoiding time and costs associated with repackaging and with replacing the battery after it is installed.
It is to be understood that the descriptions and embodiments described above are exemplary, and are not to be taken as limiting the scope of the invention. Alternatives, modifications, and variations, which do not depart from the spirit and scope of this invention, will be apparent to those skilled in the art. The scope of this invention is to be defined by the following claims:
