Method and device for determining the starting capability of a vehicle

1. A method for determining the ability of a vehicle to start, comprising the steps of:

sensing current values (I) and voltage values (U) of a battery during a predefined time window,

determining an internal resistance (R I ) of the battery by reference to the current values (I) and the voltage values (U) by means of linear regression,

determining a reference resistance value (R S ) for the starting behavior of the vehicle by reference to a maximum value (I MAX ) for the current (I) and a minimum value (U MIN ) for the voltage (U) which are sensed within the predefined time window and

determining a value which represents the ability to start by reference to a comparison between the internal resistance (R I ) and the reference resistance value (R S ).

2. The method as claimed in claim 1 , wherein a value for the internal resistance (R I ) of the battery is monitored to determine whether it drops below the reference resistance value (R S ).

3. The method as claimed in claim 2 , wherein as a function of an instantaneously determined temperature (T 1 ) of at least one of the battery and the starter circuit, the value which represents the ability to start is determined for another temperature (T 2 , T 3 ) by reference to the value, which represents this temperature (T 1 ), for the internal resistance (R I ) or reference resistance value (R S ).

4. The method as claimed in claim 1 , wherein a signal message (M) is output in when the value for the internal resistance (R I ) of the battery is equal to or greater than the reference resistance value (R S ).

5. The method according to claim 4 , wherein a temperature (T) of at least one of the battery and a starter circuit of the vehicle is determined.

6. The method according to claim 1 , wherein a temperature (T) of at least one of the battery and a starter circuit of the vehicle is determined.

7. The method as claimed in claim 1 , wherein as a function of an instantaneously determined temperature (T 1 ) of at least one of the battery and the starter circuit, the value which represents the ability to start is determined for another temperature (T 2 , T 3 ) by reference to the value, which represents this temperature (T 1 ), for the internal resistance (R I ) or reference resistance value (R S ).

8. The method as claimed in claim 1 , wherein charge start (L) of the battery is monitored and is linked to the internal resistance (R I ) of the battery in such a way that, when the value drops below a limiting value (G U ) for the internal resistance (R I ) for a given charge state (L), the battery is disconnected from the on-board electrical system.

9. A device for determining the ability of a vehicle to start, said device comprising:

a current sensor for sensing current values (I) and a voltage sensor for sensing voltage values (U) of a battery during a predefined time window;

an evaluation unit for determining an internal resistance (R I ) of the battery by reference to the current values (I) and the voltage values (U) by means of linear regression, and for determining a reference resistance value (R S ) for the starting behavior of the vehicle by reference to a maximum value (I MAX ) for the current (I) and a minimum value (U MIN ) for the voltage (U) which are sensed within the predefined time window, whereby it is possible to determine a value which represents the ability to start by reference to a comparison between the internal resistance (R I ) and the reference resistance value (R S ).

10. A method for determining the starting status of an automobile, comprising the steps of:

measuring current and voltage values of a battery;

determining an internal resistance of the battery as a function of said current and voltage values;

providing a reference resistance value as a function of a maximum current value and a minimum voltage value during a predetermined interval;

comparing said internal resistance value with said reference resistance value.

11. The method as claimed in claim 10 , wherein a value for the internal resistance (R I ) of the battery is monitored to determine whether it drops below the reference resistance value (R S ).

12. The method as claimed in claim 10 , wherein, a signal message (M) is output in when the value for the internal resistance (R I ) of the battery is equal to or greater than the reference resistance value (R S ).

13. The method according to claim 10 , wherein a temperature (T) of at least one of the battery and a starter circuit of the vehicle is determined.

14. The method as claimed in claim 10 , wherein, as a function of an instantaneously determined temperature (T 1 ) of at least one of the battery and the starter circuit, the value which represents the ability to start is determined for another temperature (T 2 , T 3 ) by reference to the value, which represents this temperature (T 1 ), for the internal resistance (R I ) or reference resistance value (R S ).

15. The method as claimed in claim 10 , wherein charge start (L) of the battery is monitored and is linked to the internal resistance (R I ) of the battery in such a way that, when the value drops below a limiting value (G U ) for the internal resistance (R I ) for a given charge state (L), the battery is disconnected from the on-board electrical system.

16. The device according to claim 9 , including means for monitoring a value for the internal resistances of the battery to determine whether said internally resistance of a battery drops below the reference resistance value.

17. The device claimed at claim 9 , further including a means for outputting a signal message when the value for the internal resistances of the battery is equal to or greater than the reference resistances value.

18. The device claimed at claim 9 , further including a sensor for determining a temperature of at least one of the battery and a starter circuit of the vehicle.