Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells
Reexamination Certificate
1999-10-27
2001-09-18
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
C320S132000
Reexamination Certificate
active
06291971
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German patent document 198 49 493.9, filed Oct. 27,1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method and apparatus for detecting the charge balance of storage batteries by summing the charging and discharging currents over time.
In known methods of this kind, the current is measured to determine the charge balance of storage batteries of a vehicle with electric drive. This current is added up or accumulated over time, for example by an integrator circuit. A procedure of this kind is described for example in German patent documents DE 31 42 038 A1 and DE 35 20 985 A1, in which the currents are detected with their proper signs and a charge and discharge balance is generated.
German patent document DE 41 12 987 A1 also utilizes a current measurement. It is mentioned as advantageous in this regard that a frequency can be generated corresponding to the current load on the battery by means of a current-frequency converter even for several consumers. The frequency in turn generates clock pulses that can be added up with their proper signs in order to determine a charge balance for the battery.
It is also known to provide a pulse generator which delivers pulses at certain time intervals, preferably for those consumers that exhibit constant current consumption when they are switched on and which are operated by a storage battery arrangement. By means of the pulse generator, the operating times of the individual consumers can be determined. Since the load current is also known during this time, the charge balance can also be determined as a result of the constant nature of the load current in the respective consumers if the storage battery arrangement is charged with a known charge current. The quantity of charge removed and the quantity of charge supplied are also determined. See for example German patent document DE 41 12 987 A1 in which individual discharge counting frequencies are assigned to the individual consumers when they are in the “ON” state.
For the sake of completeness, mention should also be made of German patent document DE 196 37 574 A1 which teaches the determination of the charge state of a storage battery by evaluating the terminal voltage of the battery. The temperature must also be taken into account. See, for example, German patent document DE 42 41 012 A1 in which the charge balance is determined by evaluating the terminal voltage of the storage battery. In this case also, the temperature must be taken into account.
One object of the present invention is to improve the accuracy of the charge balance in a vehicle with electric drive.
This goal is achieved by the charge balance detection method and apparatus according to the invention in which several current measuring arrangements are provided. Each of the individual electrical consumers is assigned to one of these current measuring arrangements, and the currents detected by the current go measuring arrangements are added over time.
Each current measuring arrangement has a measurement error which is determined essentially by the maximum current that it can detect. According to the invention, the consumers are assigned to different current measuring arrangements so that the load currents of the individual consumers are determined by the current measuring arrangements to which these consumers are assigned. In this manner load components which consume only a small current can be measured by instruments which are designed to measure small currents, and accordingly, generate a small measurement error, while load components which draw a large current are assigned to measuring instruments with a large current capacity.
For example, the electric drive has a power draw that is well into the kW range, with a comparably high associated current. The other electrical consumers on the vehicle for the most part exhibit consumption that is less than 1 kW. This is true for example for the lighting of the vehicle and an electric rear window heater that still rank with the highest electrical consumers in a vehicle. These consumers which have a power draw of several hundred watts can only be switched on when the vehicle is running.
Other consumers in the vehicle, that have a power draw in the range of several watts, are constantly active. This is true for example for a central locking system which can also be designed to be remote-controlled, or for a theft warning device.
Problems with creating a charge balance can be avoided by the method according to the invention. Such problems can occur in known devices under different operating conditions of the vehicle. When creating a charge balance with only a single current measuring arrangement, the latter must be designed so that currents can be measured at power levels within a range of several kW. This requirement can cause a corresponding measurement error; for example, when the vehicle is parked for a long interval. In such circumstances, an erroneous charge balance determination can occur because the measured currents, which correspond to a power draw of only a few watts, are below the margin of error of the current measuring arrangement. If the user of the vehicle, for example, goes on vacation without the vehicle and therefore leaves the vehicle parked for several weeks, the consumers mentioned, which are active even when the vehicle is parked, cause a non-negligible discharge of the storage battery system. When the charge balance has been erroneously determined, the storage battery arrangement can drain completely.
Advantageously, therefore, according to the invention the consumers are assigned to different current measuring arrangements corresponding to their respective power draw (which essentially corresponds to the current draw), so that the measurement errors of the current measuring arrangements are adapted to the rated currents of the individual consumers. This allocation by power draw correlates fully with whether the consumers can be activated only when the vehicle is being driven, or can be activated even when the vehicle is parked. Such an allocation of the consumers also creates a situation in which the respective current measuring arrangements are energized in accordance with the operating state of the vehicle that can be detected optimally from the measurement error standpoint.
When the vehicle is being driven, the charge balance is determined essentially by the power draw of the electric drive. In addition, the charge balance is also correctly determined in the phases in which the vehicle is at rest. This has an advantageous effect especially during longer parking times for the vehicle.
In an advantageous embodiment of the invention, two current measuring arrangements are provided, with the electric drive being assigned to one of the current measuring arrangements, and the other consumers assigned to the other current measuring arrangement. In this way, an allocation of the consumers is obtained in which those consumers whose power draw lies in the kW range are assigned to one current measuring arrangement, and the power draw of the remaining consumers is detected by means of the other current measuring arrangement which reaches up to approximately 1 kW per consumer. In known methods for determining charge balances, it has been shown that a charge balance with sufficient accuracy can be determined in this way.
In another embodiment of the invention, two current measuring arrangements are provided, with one current measuring arrangement having assigned to it, in addition to the electric drive, those consumers that can be activated only while the vehicle is operating; and the other current measuring arrangement having allocated to it those consumers that are active or can be activated even when the vehicle is at rest.
As already described, during driving the charge balance is determined essentially by the power draw of the electric drive. Since the measurement error of this current measuring arrangement also enters into t
Boll Wolf
Falkenmayer Bernd
Schorpp Matthias
Crowell & Moring LLP
Daimler-Chrysler AG
Tso Edward H.
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