EP2875235A1

EP2875235A1 - Diagnostics for a starter motor

Info

Publication number: EP2875235A1
Application number: EP13806892.9A
Authority: EP
Inventors: Holger Dreher; Gunnar Ledfelt
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2012-06-19
Filing date: 2013-06-12
Publication date: 2015-05-27
Also published as: WO2013191619A1; CN104471238A; BR112014031831A2; SE1250654A1; CN104471238B; RU2604659C2; EP2875235A4; RU2015101228A; SE536552C2

Abstract

An electric starter motor (110) is arranged so as to start a combustion engine (120). The function of the starter motor (110) is subject to diagnostics by means of measuring elements (130, 140) that measure a supply voltage (U) to the starter motor and an rpm (RPM) of the combustion engine. Based on the measured parameters (U, RPM), a processor (160) determines a status indicator (S) that provides a quality metric for the performance of the starter motor (110). A storage element (170) stores a respective value for the status indicator (S) in connection with a number of activations of the electric starter motor (110) in a data series (M). The processor (160) analyzes the data series (M) and determines, on the basis thereof, whether the function of the electric starter motor (11) is acceptable and, if the function is not determined to be acceptable, generates an error code (E).

Description

Diag nostics for a starter motor

TECHNICAL BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention generally concerns diagnostics for an electric starter motor for a combustion engine. The invention concerns in particular a system according to the preamble to claim 1 and a method according to the preamble to claim 1 1 . The invention also concerns a computer program according to claim 21 and a computer-readable medium according to claim 22.

Essentially all current motor veh icles that are equipped with combustion engines are dependent upon an electric starter motor to be able to start. The function of the starter motor is thus vital to the operation of the veh icle. Various known solutions exist for verifying this function . For practical reasons, it is preferable that it not be necessary to remove the starter motor from the veh icle to test the function of the starter motor. The function of the electric starter motor is also critical in stationary mach ines that include a combustion engine. Documents GB 2 003 281 , JP 55057659, US 2009/0309530 and US 7,409,856 describe examples of solutions for evaluating the function of an electric starter motor. Common to these solutions is that they involve determining a supply voltage to the starter motor, an rpm parameter and the current supplied to the starter motor. However, the current measurement is relatively complicated to carry out. I n addition , the measurement per se runs the risk of affecting the function of the starter motor.

Document KR 100819334 describes a method in which the battery voltage to the starter motor and an rpm generated by the starter motor constitute the only input parameters for the diagnostics function . PROBLEMS ASSOCIATED WITH THE PRI OR ART

Solutions thus do exist for evaluating the function of an electric starter motor, such as in a motor veh icle, in a workshop environment. However, no solution exists for checking , in a simple and reliable way, the functional status of an electric starter motor during the normal operation of the machine in which the starter motor is included .

SUMMARY OF THE I NVENTI ON

The object of the present invention is consequently to provide a solution to the foregoing problem that enables automatic and efficient diagnostics of an electric starter motor, where neither the starter motor nor the machine in which it is included needs to be transported to a workshop.

According to one aspect of the invention , this object is achieved by means of the system described above, wherein the system comprises a storage element configured so as to store a respective value for the status indicator in connection with a number of activations of the electric starter motor in a data series. The processor is configured so as to analyze the data series and , on the basis thereof, to determine whether the function of the electric starter motor is acceptable. If the function is not determined to be acceptable, the processor is configured so as to generate an error code, which is in turn , for example, stored and/or gives rise to an alarm. This system is advantageous because the error code need not be generated at a predetermined level for the status ind icator. The system can instead react adaptively to any trend that indicates an unfavorable evolution in terms of the performance of the starter motor. By this means, for example, unnecessary alarms and subsequent workshop visits can be avoided . The alarm is appropriately generated if the starter motor is sufficiently worn that it will need to be replaced relatively soon , with the resu lt that it will be recommended that a visit to a workshop be scheduled in response to an alarm .

According to one embodiment of this aspect of the invention , it is presumed that said number of activations of the electric motor that are contained in the data series are consecutive. Either each activation is tied to a respective time specification , or on ly one ordinal is specified for each activation. I n any event, a consecutive sequence of starter motor activations provides a good basis for analyzing the function of the starter motor. According to another embodiment of th is aspect of the invention , the processor is configured so as to analyze the data series by evaluating a rate at which the status indicator changes over time. The error code is generated either if an absolute value for the rate exceeds a first predetermined limit value or if the status indicator decreases at a rate that is faster than a second predetermined limit value. The limit values depend in their turn on whether the data series includes time information or not. Regardless of the manner employed , sufficient criteria are obtained hereby for detecting any defective function of the starter motor.

According to yet another embodiment of this aspect of the invention , the processor is configured so as to analyze the data series by calculating a mean value for the status indicator over a portion of the values in the data series, such as within a rolling measurement window. The processor is further configured so as to generate the error code if said mean value falls below a third predetermined limit value. Generation of the error code as a result of a temporary deviation in the evolution of the status indicator over time is thereby avoided . According to another embodiment of th is aspect of the invention , the processor is configured so as to take into account at least one parameter describing the cond itions under which the status indicator was generated . If the status indicator is determined to have been generated under a first type of cond itions, the processor is configured so as to guide the storage of the status indicator to a first data series. If the status indicator is instead determined to have been generated under at least one other type of cond itions, the processor is configured so as to gu ide the storage of the status indicator to at least one other data series. The processor is further configured so as to analyze said respective first and at least one other data series individually and , on the basis thereof, to determine whether the function of the electric starter motor is acceptable. The decision as to whether to generate an error code is thereby made on sufficient grounds (such as in connection with similar conditions in terms of ambient temperature, battery voltage, cold , semi-hot or hot start), with the result that the reliability of any error code can be relatively high .

According to one embod iment of this aspect of the invention , the system comprises elements for generating , on the basis of the error code: an acoustical signal that is perceived by an operator, a visual signal intended to be perceived by an operator, storing an error code in a memory unit, a signal arranged so as to be transferred to monitoring equipment connected to the system and/or a wireless signal arranged so as to be transferred via at least one communication network to a monitoring node. High flexibility in terms of the processing of the error code is achieved thereby.

According to yet another embodiment of this aspect of the invention , the system comprises at least one temperature measuring element configured so as to measure at least one temperature related to the electric starter motor. The process is here configured so as to determine the status indicator on the further basis of said at least one measured temperature. Taking the temperature into account in this way is advantageous, as environmental changes (such as those depending on seasonal variations and/or geographical cond itions) can be weighed in in the diagnostic method in a natural and adequate manner. The viscosity of the oil in the combustion engine in fact varies considerably with the temperature, which is in turn reflected in the measured rpm .

According to an add itional embodiment of this aspect of the invention , the processor is configured so as to assign the status indicator a special value indicating that the function of the starter motor cannot be determined if the measured supply voltage is below a voltage threshold . If the supply voltage is too low, it is in fact impossible to draw any conclusions as to whether the fact that the combustion engine will not start is attributable to the starter motor being faulty, or whether the fault is attributable to something else, such as insufficient battery voltage.

According to an add itional embodiment of this aspect of the invention, the measuring elements are configured so as to measure the supply voltage and the rpm during a measurement interval, and the processor is configured so as to average the supply voltage and the rpm over the measurement interval. The processor is also configured so as to determine the status indicator on the basis of an average value for the su pply voltage to the starter motor during the measurement interval and an average value for the rpm of the combustion engine during the measurement interval . The temperature measuring element is advantageously also configured so as to measure said at least one temperature during a measurement interval , and the process is configured so as to average the measured temperature over the measurement interval. The processor is here configured so as to utilize the averaged temperature in determining the status indicator. Taking the average values into account in this way is advantageous, as the instantaneous values for supply voltage, rpm and temperature can be temporarily misleading in relation to the actual cond itions. It can also be advantageous to take other parameters into account, such as a lowest measured su pply voltage to the starter motor during one compression cycle. According to another aspect of the invention , said object is achieved by means of the method described above, wherein a respective value for the status indicator in connection with a number of activations of the electric starter motor is stored in a storage element in the form of a data series. The data series is analyzed and , on the basis of said analysis, a determination is made as to whether or not the function of the electric starter motor is acceptable. An error code is generated if the function is not determined to be acceptable. The advantages of th is method and of the preferred embodiments thereof are presented in the discussion above with reference to the proposed system.

According to an additional aspect of the invention , said object is achieved by means of a computer program that is directly downloadable to the internal memory of a computer, and that comprises software for controlling the steps according to the method proposed above, wherein said program is run on a computer. The computer can in turn be represented by a control unit in the system, a diagnostics unit connected thereto, a tablet computer, a smartphone etc. According to yet another aspect of the invention , said object is achieved by means of a computer-readable medium with a program stored thereon , wherein the program is adapted so as to enable a computer to control the steps according to the method proposed above. BRI EF DESCRI PTI ON OF TH E DRAWI NGS

The present invention will now be explained in greater detail with the help of embodiments, which are described as examples, and with reference to the accompanying drawings.

Figure 1 shows a schematic depiction of a proposed system,

Figures 2a-b show graphs of examples of how the status indicator can change over time, and Figure 3 shows a flow diagram that illustrates the general method according to the invention .

DESCRI PTI ON OF EMBODI MENTS OF THE I NVENTI ON

We refer by way of introduction to Figure 1 , which shows a schematic depiction of a system according to the invention for diagnostics of an electric starter motor 1 10. The electric starter motor 1 10 is arranged so as to start a combustion engine 120, and can thus be included in a motor vehicle. However, the proposed system can just as well be integrated into a stationary machine, such as an electrical generator or stone crusher. In any case, the electric starter motor 1 10 is advantageously powered by a battery 135.

The proposed system comprises measuring elements 130 and 140, a processor 160 and a storage element 1 70. It is also advantageous if at least one temperature measuring element (not shown) is included in the system .

The measuring elements 130 and 140 are respectively configured so as to measure a supply voltage U to the starter motor 1 10 and an rpm RPM of the combustion engine 120. The rpm RPM of the combustion engine 120 will be discussed throughout in the description that follows. Because the starter motor 1 10 and the combustion engine 120 are coupled together (for example via a so-called Bendix clutch), there is naturally a correlation between the rpm of the combustion engine 120 and the rpm of the starter motor 1 10, with the resu lt that a measured rpm for the starter motor 1 10 can be utilized just as well as the proposed rpm RPM of the combustion engine 120.

The temperature measuring element is configured so as to measure at least one temperature related to the machine in which the starter motor 1 10 is included . Said at least one temperature can , for example, pertain to an ambient temperature, an oil temperature in the eng ine, a cooling fluid temperature, an engine block temperature, a starter motor temperature and/or a battery temperature. It is advantageous to register more than one temperature, as this enables a determination as to whether a cold start (all temperature essentially equal) or a hot start (the oil temperature in the engine and a cooling fluid temperature exceed the ambient temperature considerably) is taking place, or if the engine is being started in a semi-hot state (the cooling fluid temperature exceeds the ambient temperature considerably, but the oil temperature in the engine is relatively low; or the oil temperature is relatively high , but the cooling fluid temperature is relatively low).

The processor 160 is configured so as to determine, based on the su pply voltage U and rpm RPM , a status indicator S, which provides a quality metric for the performance of the starter motor 1 10. The status ind icator S is stored in the storage element 1 70. A respective value for the status indicator S is advantageously stored in connection with each activation of the electric starter motor 1 10 so that, after a time, the storage element 1 70 contains a data series M of status indicators S . The processor 160 is further configured so as to analyze the data series M and determine, on the basis thereof, whether the function of the electric starter motor 1 10 is acceptable. The processor 160 is configured so as to generate an error code E if the function is not determined to be acceptable.

Because the start conditions can vary most considerably, it is advantageous to reg ister two or more data series M in parallel, where the status indicators S within a given data series M have been generated under similar conditions, such as ambient temperature T, battery voltage U , start type (cold , semi-hot or hot). This is advantageous, as it makes it possible to determine whether a given start went worse (or better) than a previous start under corresponding circumstances. This also makes it possible for the decision regarding the generation of any error code E to be made based on adequate grounds, with the result that the reliability of the error code E is relatively high .

For example, the processor 160 can consequently be configured so as to take into account at least one parameter that describes the conditions under which the status indicator S was generated . If the status indicator S is determined to have been generated under a first type of cond itions, then the processor 1 60 is further configured so as to guide the storage of the status ind icator to a first data series in the storage element 1 70. If the status indicator S is instead determined to have been generated under a second type of conditions, then the processor 160 is configured so as to guide the storage of the status indicator S to a second data series in the storage element 1 70, and so on . The processor 160 then analyzes each data series individually and determines, on the basis thereof, whether the function of the electric motor 1 10 is acceptable. The processor 160 generates an error code E in the event that the function is not determined to be acceptable.

According to embodiments of the invention , the system also comprises elements for processing the error code E in their turn. For example, the error code E can constitute the basis for generating an acoustical and/or visual signal intended to be perceived by an operator. Alternatively, or as a complement, the error code E can be stored in a memory unit to be read out during a later workshop visit. The system can further comprise elements for generating a signal intended to be transferred to monitoring equipment (for example in a workshop) connected to the system, and/or elements for generating a wireless signal intended to be transferred by means of at least one communication network to a monitoring node. Convenient remote monitoring of the function of the electric starter motor 1 10 is thereby made possible.

Figure 2a shows a first graph of an example of how the status indicator S can change over time, wherein the horizontal axis represents a number n of activations of the starter motor 1 10 and the vertical axis represents the values for the status indicator S in a data series M . Figure 2b shows a second graph with the same values for the status indicator S, but here the horizontal axis instead represents chronological time t. The horizontal axis thus represents not only a sequence, but rather reflects a common chronolog ical distance between the values in the data series M .

According to one embodiment of the invention , the activations of the electric starter motor 1 10 that are contained in the data series M are consecutive, i.e. there are no gaps in the data series M , and the values therein are processed in the order in which they were stored .

According to one embodiment of the invention , the processor 160 is configured so as to analyze the data series M by determining a rate Rn or Rt at which the status indicator S is changing over time. The processor 160 is configured so as to generate an error code E if an absolute value of the rate Rn or Rt exceeds a first predetermined limit value E.

In Figures 2a and 2b, the rate Rn or Rt is represented by the slope of the graph . The processor 160 can advantageously be configured so as to determine the slope between two consecutive activations n of the starter motor 1 10, such as R_n- _{3: n-2} between n-3 and n-2, or R_{n : n} + i between n and n+1 . As can be seen , the rates Rn and Rt (or the slope of the graph) between two consecutive activations can vary depending on whether the graph specifically represents a sequence (as in Figure 2a) or if the graph also shows a common chronological distance between the values in the data series M (as in Figure 2b). For example, the slope of the graph R_t-3 t-2 between a measurement instance t_-3 and a measurement instance t_-2 respectively corresponding to the activations n-3 and n-2 is relatively flat, while the slope of the graph R_n._3:n.₂ between n-3 and n-2 is relatively steep. On the other hand , the slope of the graph R_{t0 :}ti between a measurement instance t₀ and a measurement instance t respectively corresponding to the activations n+1 is relatively steep, while the slope of the graph R_{n : n} + i between n and n + 1 is relatively flat. The first predetermined limit value at wh ich the processor 1 60 is configured so as to generate the error code E will thus depend on whether, in add ition to representing a sequence, the data series M also includes information concerning a common chronolog ical d istance between the values.

Although a sudden positive evolution of the status indicator S may indicate an anomaly in the function of the starter motor 1 10, a negative evolution is typically more problematic. According to one embodiment of the invention , the processor 160 consequently reacts on ly to a negative evolution of the values of the status ind icator S. Specifically, this means that the processor 160 is configured so as to analyze the data series M by determining a rate Rn or Rt at which the status ind icator S is changing over time. The processor 160 is configured so as to generate the error code E if the status indicator S decreases at a rate Rn or Rt that is faster than a second predetermined limit value. For the same reasons as above, the second predetermined limit value will also depend on whether the data series M only represents a sequence, or if it also includes common chronolog ical distances between the values in the data series M .

According to one embodiment of the invention , the processor 160 is configured so as to analyze the data series M by calculating an mean value S_M for the status indicator S over a portion of the values in the data series M , such as within a rolling measurement window representing a certain number n of measurement values or a certain time t. The processor 160 is configured so as to generate the error code E if the mean value S_M is less than a third predetermined limit value.

According to one preferred embodiment of the invention , the processor 160 is configured so as to determine a status indicator S on the further basis of one or a plurality of the aforementioned temperatures. For greater reliability/robustness, the measuring elements 130 and 140 are suitably configured so as to measure the technical parameters during a measurement interval, such as 1 second , during which measurement interval , for example, 10 separate measurements are registered . Alternatively, the measurement interval can be adaptively linked to one or a plurality of compression cycles of the combustion engine 120, so that the measurement interval represents a whole number of compression cycles. A typical compression cycle is roughly 15 ms long . As an alternative to a pure averaging of the rpm RPM , the processor 1 60 can in such cases be configured so as to register the lowest rpm during a compression cycle. Start performance has in fact shown itself to be dependent upon the speed at wh ich it is lowest. Furthermore, the processor 160 can be configured so as to generate averages between a respective lowest measured supply voltage U to the starter motor 1 1 0 in each of a number of compression cycles.

The processor 160 can thus be configured so as to generate averages of the measured parameters U and RPM over the measurement interval and determine the status indicator S on the basis of an average of the supply voltage U_aVg to the starter motor 1 10 during the measurement interval and an average of the rpm RPM_avg of the combustion engine 120 during the measurement interval.

In a corresponding manner, the temperature measuring element is su itably configured so as to measure at least one temperature during a measurement interval . If such is the case, the processor 1 60 is naturally configured so as to generate the average for said at least one measured temperature over the measurement interval , and to utilize at least one of said at least one averaged temperatures in determining the status indicator S. It may further be advantageous to adapt the diagnostic method performed by the processor 160 in dependence upon seasonal variations. For example, a temperature adaptation can be performed in two steps (summer/winter), in multiple steps (such as below -25°C, between -25°C and -20°C, between -20°C and - 10°C, between -10°C and ±0°C, between ±0°C and 1 0°C, and above 1 0°C), or continuously on the basis of a defined relationship: RPM_eXp = U χ P 1 /(T + P2), where RPM_eXp designates the expected rpm , U designates the measured supply voltage to the starter motor 1 10, T designates a measured temperature and P 1 and P2 are adaptation parameters.

It is advantageous to calculate the status ind icator S continuously by comparing a measured rpm RPM to an expected rpm, and to apply at least one threshold level (for example a first level representing acceptable starter motor function OK and a second level corresponding to unacceptable starter motor function NOT), for example according to the relationship below:

RPM ₊ MKT)

U / N2(T) where

RPM designates a measured rpm during a start attempt, T designates a measured temperature (such as a characteristic engine temperature),

U designates a measured supply voltage during the start attempt,

N 1 (T) designates an rpm offset at the temperature T, and

N2(T) designates an rpm parameter at the temperature T.

In the above equation , the status indicator S = 80 if the function of the starter motor is good . S > 70 can thus correspond to an acceptable starter motor function OK. If, on the other hand , S < 70, the starter motor function is considered to be unacceptable. If the trend for the status indicator S does not reverse, or at least stabilize, replacing the starter motor is consequently recommended in th is case.

If the measured supply voltage U is below a voltage threshold, it is impossible to determine the function of the starter motor. According to one embodiment of the invention , the processor 160 is consequently configured in such cases to assign the status indicator S a certain value indicating that the function of the starter motor cannot be determined . The processor 160 is suitably controlled so as to function in accordance with the foregoing by means of a computer program stored in a memory unit 180, which is either contained in the processor 160 or commun icatively connected therewith .

To summarize, the general method according to the invention will now be described with reference to the flow diagram in Figure 3.

In a first step 310, a determination is made as to whether the starter motor has been activated . If such is not the case, the process loops back and stops at step 310. Otherwise there follows a step 320, which reg isters a measured rpm of the combustion engine. As described above, the rpm is suitably registered during one measurement interval, which can be synchronized with one or a plurality of compression cycles. In parallel with step 320, a step 330 reg isters a su pply voltage to the starter motor.

A step 340 then determines a status ind icator for the starter motor based on the measured parameters: rpm and su pply voltage. The status indicator provides a quality metric for the current performance of the starter motor. A step 350 then stores a value for the status indicator in a storage element, after which a step 360 determines whether there are at least two status indicators stored in the storage element in the form of a data series. If such is the case, there follows a step 370. Otherwise the process loops back to step 310.

In step 370 the data series is analyzed and an overall function of the starter motor is estimated . A determination as to whether the function is acceptable or not is then made in a step 380. If the function is determined to be acceptable, the process loops back to step 310. Otherwise there follows a step 390, in which an error code is generated . The process then loops back to step 310.

The method steps described with reference to Figure 3 can be controlled by means of a programmed computer device. Furthermore, although the embodiments of the invention described above with reference to the figures comprise a computer and processes performed in a computer, the invention extends to a computer program, particularly a computer program on or in a carrier adapted so as to implement the invention practically. The program can be in the form of source code, object code, a code that constitutes something intermed iate between source and object code, such as code in partly compiled form, or in any other form whatsoever that is suitable for use in implementing the process according to the invention . The carrier can be any arbitrary entity or device that is capable of serving as a medium for the program . For example, the carrier can comprise a storage med ium such as a flash memory, a ROM (Read Only Memory) , for example a CD (Compact Disc) or a semiconductor-ROM , EPROM (Electrically Programmable ROM), EEPROM (Erasable EPROM) , or a magnetic record ing medium such as a floppy disk or hard drive. The carrier can also be a transmitted carrier such as an electrical or optical signal , which can be conducted through an electrical or optical cable or by radio in some other way. If the program is realized as a signal that can be conducted directly by a cable or other device or element, the carrier can consist of such a cable, device or element. Alternatively, the carrier can be an integrated circuit in which the program is embedded , wherein the integrated circu it is adapted so as to perform , or to be used in connection with the performance of, the relevant processes.

The invention is not limited to the embodiments described with reference to the figures, but rather can be varied freely within the scope of the following claims.

Claims

1 . A system for diagnostics for an electric starter motor (1 10) that is arranged so as to start a combustion engine (120), which system comprises:

measuring elements (130, 140) configured so as to measure a supply voltage (U) to the electric starter motor and an rpm (RPM) of the combustion engine, and

a processor (160) configured so as to determine, based on the measured supply voltage (U) and the measured rpm (RPM), a status ind icator (S) for the starter motor (1 10), which status indicator (S) provides a quality metric for the performance of the starter motor (1 10) , characterized i n that

the system comprises a storage element (1 70) configured so as to store a respective value for the status indicator (S) in connection with a number of activations of the electric starter motor (1 1 0) in a data series (M), and

the processor (1 60) is configured so as to analyze the data series (M), determine on the basis thereof whether the function of the electric starter motor (1 10) is acceptable and , if the function is not determined to be acceptable, generate an error code (E).

2. The system according to claim 1 , wherein said number of activations of the electric starter motor (1 10) that are contained in the data series (M) are consecutive.

3. The system according to any of claims 1 or 2, wherein the processor (160) is configured so as to analyze the data series (M) by determining a rate (Rn; Rt) at which the status indicator (S) is changing over time, and to generate the error code (E) if an absolute value of the rate (Rn ; Rt) exceeds first predetermined limit value.

4. The system according to any of claims 1 or 2, wherein the processor (160) is configured so as to analyze the data series (M) by determining a rate (Rn; Rt) at which the status indicator (S) is changing over time, and to generate the error code (E) if the status indicator (S) is decreasing at a rate (Rn ; Rt) that is faster than a second predetermined limit value.

5. The system according to any of the preceding claims, wherein the processor (160) is configured so as to analyze the data series (M) by calculating a mean value (S_M) for the status indicator (S) over a portion of the values in the data series (M) , and to generate the error code (E) if the mean value (S_M) is less than a th ird predetermined limit value.

6. The system according to any of the preceding claims, wherein the processor (160) is configured so as to:

take into account at least one parameter describing the cond itions under wh ich the status indicator (S) was generated , guide the storage of the status indicator (S) to a first data series if the status indicator (S) was generated under a first type of conditions,

guide the storage of the status indicator (S) to at least one other data series if the status ind icator (S) was generated under at least one other type of cond itions,

analyze said first and at least one other data series individually and , on the basis thereof,

determine whether the function of the electric starter motor (1 10) is acceptable.

7. The system according to any of the preceding claims comprising elements for generating , on the basis of the error code

(E), at least one of: an acoustical signal intended to be perceived by an operator, storing an error code in a memory unit, a signal arranged so as to be transferred to monitoring equipment connected to the system and a wireless signal arranged so as to be transferred by means of at least one communication network to a monitoring node.

8. The system according to any of the preceding claims, wherein:

the system comprises temperature measuring elements (150) configured so as to measure a temperature related to the electric starter motor ( 1 10) , and

the processor (1 60) is configured so as to determine the status indicator (S) on the further basis of said at least one measured temperature.

9. The system according to any of the preceding claims, wherein

the measuring elements (130, 140) are configured so as to measure the supply voltage (U) and the rpm (RPM) during a measurement interval, and

the processor (160) is configured so as to: average the supply voltage (U) and rpm (RPM) over the measurement interval and determine the status ind icator (S) on the basis of an average value for the supply voltage (U_avg) to the starter motor (1 10) during the measurement interval and an average value for the rpm (RPM_avg) of the combustion engine during the measurement interval.

10. The system according to claim 8, wherein the processor is configured so as to assign the status indicator (S) a special value indicating that the function of the starter motor cannot be determined if the measured supply voltage (U_avg) is below a voltage threshold .

1 1 . A method for d iagnostics for an electric starter motor (1 10) arranged so as to start a combustion engine (120), which method comprises:

measuring a su pply voltage (U) to the starter motor and an rpm (RPM) of the combustion engine, and

determining a status ind icator (S) for the starter motor

(1 10) based on the measured su pply voltage (U) and the measured rpm (RPM), where the status indicator (S) provides a quality metric for the performance of the starter motor ( 1 10), characterized by:

storage in a storage element (1 70) of a respective value for the status indicator (S) in connection with a number of activations of the electric starter motor (1 10), where said values constitute a data series (M),

analysis of the data series (M),

a determination as to whether the function of the electric starter motor (1 10) is acceptable on the basis of said analysis and , if the function is not determined to be acceptable,

generation of an error code (E).

12. The method according to claim 1 1 , wherein said number of activations of the electric starter motor (1 10) that the data series (M) contains are consecutive.

13. The method according to any of claims 1 1 or 12, wherein the analysis of the data series (M) comprises determining a rate

(Rn ; Rt) at which the status indicator (S) is changing over time, and wherein the error code (E) is generated if an absolute value of the rate (Rn ; Rt) exceeds a first predetermined limit value.

14. The method according to any of claims 1 1 or 12, wherein the analysis of the data series (M) comprises determining a rate

(Rn ; Rt) at which the status indicator (S) is changing over time, and where the error code (E) is generated if the status indicator (S) is decreasing at a rate (Rn ; Rt) that is faster than a predetermined second limit value.

15. The method according to any of claims 1 1 till 14, wherein the analysis of the data series (M) comprises calculating a mean value (S_M) for the status ind icator (S) over a portion of the values in the data series (M) , and wherein the error code (E) is generated if the mean value (S_M) is below a third predetermined limit value.

16. The method according to any of claims 1 1 to 15, comprising : the taking into account of at least one parameter describing the cond itions under which the status indicator (S) was generated ,

storage of the status indicator (S) in a first data series if the status indicator (S) was generated under a first type of conditions,

storage of the status ind icator (S) in at least one other data series if the status indicator (S) was generated under at least one other type of conditions,

individual analysis of said respective first and at least one other data series and , on the basis thereof,

a determination as to whether the function of the electric starter motor (1 10) is acceptable.

1 7. The method according to any of claims 1 1 to 16, comprising the generation, on the basis of the error code (E), of at least one of: an acoustical signal intended to be perceived by an operator, storing an error code in a memory unit, a signal arranged so as to be transferred to monitoring equipment connected to the system and a wireless signal arranged so as to be transferred by means of at least one communication network to a monitoring node.

18. The method according to any of claims 1 1 to 1 7, comprising , measurement of at least one temperature related to the electric starter motor ( 1 10) , and

determination of the status indicator (S) on the further basis of said at least one measured temperature.

19. The method according to any of claims 1 1 to 18, comprising : measurement of the supply voltage (U) and the rpm (RPM) during a measurement interval,

averaging of the supply voltage (U) and the rpm (RPM) during a measurement interval over the measurement interval, and

utilizing the averaged supply voltage (U_avg) and the rpm (RPMav_g) in determining the status indicator (S).

20. The method according to claim 19, comprising assigning the status indicator (S) a special value indicating that the function of the starter motor cannot be determined if the measured supply voltage (U_avg) is below a voltage threshold .

21 . A computer program that is directly downloadable to the internal memory (180) of a computer and comprises software to control the steps according to any of claims 1 1 to 20 when said program is run on the computer.

22. A computer-readable medium (180) with a program stored thereon , wherein the program is adapted so as to enable a computer to control the steps according to any of claims 1 1 to 20.