Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Patent
1992-06-08
1994-05-03
Hickey, R. J.
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
320 13, H02J 710
Patent
active
053090802
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates generally to a control unit for a battery-operated device.
BACKGROUND:
It is known that battery-operated devices that are equipped with rechargeable batteries are, connected to a charging unit for recharging the battery. The charging units are often equipped in such a way that they can be used for fast charging of the battery. In fast battery charging, however, considerable heating of the battery occurs toward the end of the charging process, to indicate that the battery is charged. A temperature sensor is connected to the battery by a thermal coupling to protect the battery against damage, such as overcharging. The temperature sensor detects the battery temperature so that the charging unit is turned off once a limit temperature is reached.
In practice, this means that charging the battery requires at least a third line, which leads to a corresponding control input to the charging unit. During battery operation of the electric unit, this control line is not needed.
From German Patent Application 25 20 599 (A1), assigned to General Electric Co. a circuit arrangement for charging storage batteries is known in which the temperature of both the storage battery and its surroundings is measured The charging current is determined as a function of the temperature difference.
From British Patent 2,088,158, corresponding to U.S. Pat. No. 4,507,368 a battery unit is known in which a bimetallic switch is thermally coupled to the battery, and when a temperature limit value is reached, it can interrupt the current circuit to the battery, both in charging and discharging operation.
THE INVENTION
The control unit according to the invention, has the advantage over the prior art that the control line not used in battery operation can now be used for other functions It is especially advantageous that monitoring of the battery with respect to drawing too much current during battery operation of the unit is possible.
It is especially advantageous that the evaluation circuit reacts to temperature changes of the temperature sensor. Since the temperature of the battery changes relatively slowly, brief interfering signals can easily be stabilized, so that if a predetermined limit value is exceeded, the output signal is still reliable. Particularly simple evaluation circuits are obtained if comparators are used, to the output of which suitable displays can be connected without major effort.
It is also advantageous that the evaluation circuit not only detects the static temperature but also measures the temperature gradient, so that it can evaluate a rapid or not so rapid temperature rise. The temperature gradient can advantageously be measured with a differentiation element that has only a few components.
The control unit becomes especially advantageous if the time constant of the differentiation element is variable. This allows simple adaptation of the control unit to various types of battery or conditions of use of the battery-operated device, particularly to the thermal time constants of an electric motor used. Resistors that change their resistance as a function of temperature have proved themselves as sensors.
Moving parts are not needed. To save battery power, it is favorable if the display is one that can be turned off. If an overload situation with respect to the battery or the electric unit arises, which was recognized by the exceeding of one of the predetermined limits, then advantageously the battery or the electric device is shut off.
Further advantages of the invention can be inferred from the description.
DRAWINGS
An exemplary embodiment of the invention is shown in the drawing and described in further detail in the description below.
FIG. 1 shows a battery with a charging unit;
FIG. 2 shows a battery with an electric tool; and
FIG. 3 shows an exemplary embodiment of the invention.
FIG. 4 shows another exemplary embodiment of the invention.
DETAILED DESCRIPTIONS
It is known that rechargeable batteries 2, for instance nickel-cadmium cells (NC cells), can be cha
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Fiebig Armin
Odendahl Alfred
Hickey R. J.
Robert & Bosch GmbH
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