Electricity: battery or capacitor charging or discharging – Battery or cell charging – With thermal condition detection
Reexamination Certificate
2000-02-03
2002-01-22
Toatley, Jr., Gregory J (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
With thermal condition detection
C320S130000, C219S201000
Reexamination Certificate
active
06340879
ABSTRACT:
BACKGROUND OF THE INVENTION
A known disadvantage in batteries of all types is that their internal electrochemical reaction, and thus the maximum utilizable output, basically depends very heavily on the battery's internal temperature. When the temperature drops, the speed of the chemical reaction in the electrons decreases. This lowers the maximum electrical current which the battery is able to supply during constant no-load voltage, and thus the battery's output. Furthermore the speed of the mass transfer within the electrolyte and within the porous battery electrodes decreases. Both factors considerably increase the internal resistance of the cold battery. This means that in a supercooled condition of the cells even a fully charged battery is unable to supply all of its nominal electrical output because of its high internal resistance. However the nominal output can be obtained again without adding any charging energy as soon as the battery warms up to normal temperature.
The temperature dependence is also especially disadvantageous for example when the battery has to supply a D.C. voltage transformer where a predetermined electrical output is obtained from the secondary side, regardless of the voltage at the battery contacts. The transmission operation of a radio telephone for example requires an electrical output of a few watts for the power amplifier. Because of the high internal resistance, the voltage at the battery contacts is low and the transformer control causes an increase in current consumption in order to provide the required output. This in turn causes a further voltage reduction at the contacts. Since the transformer does not receive sufficient output, its control is interrupted and goes into an uncontrolled operating mode which corresponds to a total battery discharge.
For example if the transformer is used for a radio telephone, its control perceives this operating condition as a discharged battery and switches the radio telephone to the stand-by mode to protect it from becoming fully discharged. Although the battery is still sufficiently charged, it is impossible in this mode to establish a connection to the network. This situation represents a considerable safety risk for the emergency call function of the radio telephone.
It is known for example to protect motor vehicle starter batteries as long as possible against supercooling by adding a casing of a good thermal insulation material. Various sellers offer such a casing as a car accessory. However, on the one hand this requires a large additional volume and on the other it only provides a time-limited effect. The solution is especially unsatisfactory for a radio telephone because an additional casing undesirably increases the volume of the telephone.
To extend this effect, electronically controlled heating plates can be found in the auto accessories market. They are cemented to the surface of the starter battery housing and have electrical connectors which must be connected to the battery contacts. Such a heating plate prevents cooling of the battery by using its own power, so that its internal temperature remains in a range where the internal resistance is low enough so that the desired output can be obtained at any time.
For reasons of electrical insulation however, the cells of a battery are encased in a material which is also a good heat insulator. This causes a high thermal resistance between the inside of the battery and the heating plate and the battery's environment is kept warm at a considerable cost of electric power to prevent a decrease in its internal temperature. Due to the high thermal resistance however, it is not possible to reactivate a supercooled battery with justifiable cost of time and energy. At low temperatures therefore the heating plate always supplies a significantly higher amount of power to the environment than is required by the inside. This can overtax the battery's capacity. There is the danger that so much power has already been used to maintain the normal temperature that it is no longer possible to establish a connection because the battery is discharged.
It is also known from applicable safety provisions for the safe handling of batteries, such as the IEC recommendations for example, that an external short circuit of the connections of a battery must be strictly avoided. As can be found on the Varta Company internet site: “Basics on the subject of batteries. Additional questions for advanced students, “http//www.varta.de/knowhow/100quest/100-003.html 7”, an external short circuit can have serious consequences if high gas pressure builds up inside the battery.
To carefully charge a radio telephone's battery it is known to place a temperature sensor in the battery between the insulating external skin and the metallic cell body. The radio telephone's control circuit uses this sensor to determine the battery's temperature with a relatively small delay because of the metallic contact, and then interrupts the charging if the battery has been heated to a predetermined degree. This protects against overcharging.
In the area of video technology, compare for example Philips' correspondence lessons: Electrical technology and Electronics, Volume 2, Technique and Application, the heavily reworked 8th. issue, section “Horizontal Deflection Steps”, pages 231 ff, Heidelberg: Hüthig, which describes a simple functional principle for producing a sawtooth-shaped alternating current for horizontal deflection, from a direct current source such as a battery. In principle the direct current source has an inductance in series with a switch, which is bridged by a diode and conducts and blocks with alternating current. A capacitance is in parallel with the inductance. With the appropriate choice of component values in relation to the switching times of the switch, the following takes place: During the time the switch is conducting, a current from the battery builds a magnetic field in the inductance. It collapses after the switch blocks the current, which reverses its direction and the battery power oscillates in the form of a resonance vibration half-wave between the inductance and the capacitance and back. During this half-wave the voltage amplitude is still positive. The subsequent negative half-wave opens the diode and with ideal, namely loss-free components, the battery power flows back into the battery. The process is therefore also called “power recovery”.
SUMMARY OF THE INVENTION
One advantage of the present invention is that it can be used regardless of cell type, cell size and the battery's structural form. The invention is particularly suited for batteries which are used to supply power to mobile devices suc as radio telephones or radio device, since the device can operate again after a few minutes. This makes it possible, for example, to make an emergency call with a radio telephone in dangerous situations, even under the effect of extreme cold such as takes place in polar regions or in Alpine areas. The content “radio telephone” is used in the present case as a generic term for all types of devices for wireless communication, particularly mobile telephones, car telephones, satellite telephones, mobile fax machines and mobile computers which can communicate with a network.
Starting with the defects of the known solutions for reactivating a battery, the object of the invention is to create a solution for a radio telephone which, with a justifiable expense of time and energy enables the use of the radio telephone as fast as possible after the effect of extremely low temperatures, or keeps the telephone in operating condition.
The reactivation of the battery takes place according to the invention through the internal heating of the electrolyte, which is done with the aid of a time-controlled intrinsic current via the battery contacts, where the external circuit transforms a negligibly small electrical power. The high internal resistance, which operates as an internal heating element, is used against supercooling. The amount of electrical power
Nokia Mobile Phones Ltd.
Toatley Jr. Gregory J
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