Method for checking a connection between a low-voltage supply system and a battery, and motor vehicle
A process to check a connection between a battery ( 2 ) supplying a low-voltage network ( 1 ) of a motor vehicle ( 12 ), the voltage of which is less than the voltage of a high-voltage network ( 6 ) of the motor vehicle ( 12 ), and the low-voltage network ( 1 ); wherein a DC voltage converter ( 5 ), which is configured for exchanging electrical power between the high-voltage network ( 6 ) and the low-voltage network ( 1 ), connects the high-voltage network ( 6 ) to the low-voltage network ( 1 ); wherein a DC voltage converter ( 5 ) modulates the output voltage into the low-voltage network at a modulation frequency; wherein the current hereby applied and the voltage hereby applied are measured by the battery ( 2 ), and a resistance value is determined and evaluated with respect to at least one connection criterion, according to which a connection fault is determined when at least one connection criterion is not fulfilled.
1. A method of checking a connection between a battery supplying a low-voltage network of a motor vehicle, a voltage of which is lower than a voltage of a high-voltage network of the motor vehicle, and the low-voltage network, the method comprising:
connecting the high-voltage network to the low-voltage network, using a DC voltage converter that is configured for exchanging electrical power between the high-voltage network and the low-voltage network;
evaluating a resistance value with respect to at least one connection criterion; and
determining a connection fault when at least one connection criterion is not fulfilled,
wherein at least one connection criterion is a check of whether a resistance is less than a resistance threshold value, the check based on a triggering event that includes a critical operating situation of the low-voltage network, wherein a critical operating situation is detected at least when at least one predetermined, in particular safety-relevant load can no longer be supplied solely by the DC voltage converter from the high-voltage network.
2. The method according to claim 1 , wherein the check is made as a connection criterion to determine whether the resistance is less than a resistance threshold value in a range from 25 to 50 mOhm and/or whether a fluctuation value derived from the chronological progression of the resistance is less than a fluctuation threshold value.
3. The method according to claim 1 , wherein multiple modulation frequencies are used simultaneously and/or in chronological sequence, and/or the modulation is sinusoidal.
4. The method according to claim 1 , wherein the modulation frequency is selected in a frequency band from 50 to 200 Hz and/or the amplitudes of the modulation are less than 10% of the absolute voltage of the DC voltage portion of the DC voltage converter, and/or the DC voltage portion of the output voltage of the DC voltage converter is selected as a function of the charge state of the battery.
5. The method according to claim 2 , wherein the check takes place cyclically or continuously or is triggered based on a triggering event.
6. The method according to claim 5 , wherein a starting of the motor vehicle and/or the detection of a critical operating situation of the low-voltage network is used as the triggering event.
7. The method according to claim 1 , wherein a corresponding message is generated and output to the driver of the motor vehicle in the event of a determined connection fault.
8. The method according to claim 1 , wherein a resistance measurement is also conducted at the DC voltage converter, and its connection to the low-voltage network is checked.
9. A motor vehicle, comprising:
a low-voltage network;
a high-voltage network, a voltage of which is greater than a voltage of the low-voltage network;
a battery supplying the low-voltage network;
a DC voltage converter connecting the high-voltage network with the low-voltage network, which DC voltage converter is configured to exchange electrical power between the high-voltage network and the low-voltage network; and
at least one control unit which is configured to execute a process to check a connection between the battery supplying the low-voltage network of the motor vehicle, the voltage of which is lower than the voltage of the high-voltage network of the motor vehicle, and the low-voltage network,
wherein a DC voltage converter connects the high-voltage network to the low-voltage network, the DC voltage converter modulates an output voltage into the low-voltage network at a modulation frequency, wherein a current hereby applied and a voltage hereby applied are at the battery, a resistance value is determined from a measured voltage and a measured current, and the resistance value is evaluated with respect to at least one connection criterion, according to which a connection fault is determined when at least one connection criterion is not fulfilled,
wherein the check is triggered based on a triggering event, and wherein a critical operating situation is detected at least when at least one predetermined, in particular safety-relevant load can no longer be supplied solely by the DC voltage converter from the high-voltage network.
10. The motor vehicle of claim 9 , wherein a starting of the motor vehicle and/or the detection of a critical operating situation of the low-voltage network is used as the triggering event.
11. A method of checking a connection between a battery supplying a low-voltage network of a motor vehicle, a voltage of which is lower than a voltage of a high-voltage network of the motor vehicle, and the low-voltage network, the method comprising:
connecting the high-voltage network to the low-voltage network, using a DC voltage converter that is configured for exchanging electrical power between the high-voltage network and the low-voltage network;
modulating, via the DC voltage converter, an output voltage into the low-voltage network at a modulation frequency;
wherein a current hereby applied and a voltage hereby applied are at the battery;
determining a resistance value from a measured voltage and a measured current;
evaluating the resistance value with respect to at least one connection criterion; and
determining a connection fault when at least one connection criterion is not fulfilled,
wherein at least one connection criterion is a check of whether a resistance is less than a resistance threshold value, the check based on a triggering event that includes a critical operating situation of the low-voltage network, wherein a critical operating situation is detected at least when at least one predetermined, in particular safety-relevant load can no longer be supplied solely by the DC voltage converter from the high-voltage network.
12. The method according to claim 11 , wherein a check is made as a connection criterion to determine whether the resistance is less than a resistance threshold value in a range from 25 to 50 mOhm and/or whether a fluctuation value derived from the chronological progression of the resistance is less than a fluctuation threshold value.
13. The method according to claim 11 , wherein multiple modulation frequencies are used simultaneously and/or in chronological sequence, and/or the modulation is sinusoidal.
14. The method according to claim 11 , wherein the modulation frequency is selected in a frequency band from 50 to 200 Hz and/or the amplitudes of the modulation are less than 10% of the absolute voltage of the DC voltage portion of the DC voltage converter, and/or the DC voltage portion of the output voltage of the DC voltage converter is selected as a function of the charge state of the battery.
15. The method according to claim 12 , wherein the check takes place cyclically or continuously.
16. The method according to claim 11 , wherein a corresponding message is generated and output to the driver of the motor vehicle in the event of a determined connection fault.
17. The method according to claim 11 , wherein a resistance measurement is also conducted at the DC voltage converter, and its connection to the low-voltage network is checked.