Vehicle battery condition monitoring system

• US 6,417,668 B1
• Filed: 01/31/2001
• Issued: 07/09/2002
• Est. Priority Date: 01/31/2001
• Status: Expired due to Term

• Current Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Original Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Inventors: Howard, Charles E., Baker, James D., West, Keith E., Gremaux, Douglas A., Kelwaski, H. Edward
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/774,412
• Time in Patent Office: 524 Days
• Field of Search: 324/426, 324/427, 324/428, 324/429, 324/430, 324/431, 320/134, 320/136
• US Class Current: 324/426
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/14 for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle

Abstract

A method and an apparatus for monitoring a vehicle battery installed on a motor vehicle and indicating the condition of the battery is provided which does not require removal of the battery from the vehicle. Upon initial movement of the ignition key from off to on, open circuit voltage is measured and compared to an allowable range. If open circuit voltage is acceptable, the possibility that polarization is skewing the result is determined, and if the possibility is indicated, a load test is imposed on the engine. Results of testing are maintained as data records to provide updates of the comparison values used for subsequent tests.

Claims

1. Apparatus for monitoring a battery having negative and positive terminals, comprising:

a current sensor connected to a terminal of the battery for measuring current passing into and out of the battery;

a voltmeter connected across the terminals of the battery for measuring battery voltage;

a temperature sensor located near the battery for providing readings of ambient temperature;

a data processing system receiving data from the current sensor, the voltmeter and the temperature sensor and including memory for the storage of programs and data;

an engine starter system coupled for energization by the battery;

a battery history table including records of battery condition during prior starts of the apparatus;

an engine cranking power specification table;

stored in the memory for providing an estimate of cranking power required to start an engine;

a battery capacity table stored in the memory for providing estimates of battery capacity as a function of battery history, ambient temperature, open circuit voltage of the battery, voltage after a period T of cranking and current discharge during cranking; and

a comparator utilizing the estimate of cranking power and an estimate of battery capacity as inputs to determine if battery capacity exceeds the cranking power estimate.

2. Apparatus as claimed in claim 1, further comprising:

means for measuring the time lapse since an immediately prior start of the apparatus;

means responsive to the measurement of the time lapse for providing a battery capacity estimate as a function of open circuit voltage when the measured time lapse exceeds a minimum period; and

means responsive to the measurement of the time lapse falling below the minimum for indicating need for engaging the engine starter system to provide a load test of the battery.

3. Apparatus as claimed in claim 2, wherein the minimum period is long enough to exceed the period required for substantially all polarization effects in the batter to dissipate.

4. Apparatus as claimed in claim 3, further comprising:

means responsive to a determination of the comparator that battery capacity exceeds the engine cranking requirement for recording a time and date stamped record in the battery history and further responsive to the opposite determination to indicate a need for maintenance of the battery.

5. Apparatus as claimed in claim 4, wherein the means for providing a battery capacity estimate as a function of open circuit voltage utilizes the measurement of open circuit voltage as a value in a second order polynomial equation of the form

6. Apparatus as claimed in claim 5, wherein A>

>

0.3351, B>

>

−

7.0154 and C>

>

36.195.

7. Apparatus as claimed in claim 2, and further comprising the current sensor being connected to the negative terminal of the vehicle battery to detect current into and out of the battery undergoing testing.

8. A method of monitoring a vehicle battery installed on a motor vehicle, the method comprising the steps of:

(a) measuring an open circuit voltage for the vehicle battery and the ambient temperature;

(b) providing a table of allowable open circuit voltage ranges as a function of ambient temperature;

(c) comparing the open circuit voltage to an allowable open circuit voltage range for the ambient temperature;

(d) responsive to the open circuit voltage falling within the allowable open circuit voltage range, determining if sufficient time has passed since the most recent execution of the routine to avoid polarization effects on the measured open circuit voltage;

(e) responsive to time since the last start indicating possible polarization effects on the measured open circuit voltage of the vehicle battery, imposing a load on the vehicle battery by engaging an engine starter system;

(f) a period T after the engine starter system has been engaged, measuring voltage across the terminals of the vehicle battery and current from the vehicle battery under the load;

(g) providing a specification table indicating battery capacity as a function of the results of the load test;

(h) applying the results of the load test to the battery specification table to obtain a capacity figure for the vehicle battery;

(i) providing an engine required cranking power specification using engine sensor measurements as inputs; and

(j) comparing the capacity figure for the vehicle battery to an engine required cranking power figure obtained from the engine required cranking power specification and indicating the result of the comparison.

9. A method as set forth in claim 8, and further comprising saving a record of the results of the battery test in a battery history table responsive to the result of the step (j) indicating battery capacity exceeds the engine required cranking power figure.

10. A method as set forth in claim 9, wherein battery current for the load test is measured from the voltage drop across a ground wire from the negative terminal of the battery to chassis ground.

11. A method as set forth in claim 8, wherein responsive to the open circuit voltage falling outside the allowable open circuit voltage range in step (c), aborting the method and indicating need for battery maintenance.

12. A method as set forth in claim 11, wherein responsive to a counter indication of possible polarization in the vehicle battery, determining a proportion of battery state of charge by solution of a second order polynomial equation of the form

13. A method as set forth in claim 12, wherein A>

>

0.3351, B>

>

−

7.0154 and C>

>

36.195.

14. A method as set forth in claim 12 further comprising, responsive to solution of the polynomial equation to obtain a proportion of the battery state of charge, substituting that result for the results of a load test in executing step (i).

15. A method as set forth in claim 14, further comprising saving a record of the results of the battery test in a battery history table responsive to the result of the step (j) indicating battery capacity exceeds the engine required cranking power figure.

16. A method as set forth in claim 15, wherein the battery history table includes a record for each start and successful test of the vehicle battery, with the records being ordered and each record including the measured open circuit voltage and a state of charge metric.

17. A method as set forth in claim 16, wherein the battery specification table for battery capacity includes battery ratings at ambient temperature correlated with records in the battery history table.

18. A method as set forth in claim 17, where the engine required cranking power specification is addressed using measurements for ambient temperature, coolant temperature and engine lubricant temperature as well as engine history.

19. Apparatus for monitoring a vehicle battery installed on a motor vehicle, comprising:

a voltage sensor providing for measuring voltage across the terminals of the vehicle battery;

an ambient temperature sensor;

a battery current sensor;

a data processing system including memory;

a table of allowable open circuit voltage ranges as a function of ambient temperature stored in memory;

a first comparator executable on the data processing system taking an open circuit voltage provided by the voltage sensor as an input and an entry from the table of allowable open circuit voltage ranges as another input to determine if the open circuit voltage falls within the allowable open circuit voltage range;

a timer, responsive to the open circuit voltage falling within the allowable open circuit voltage range, for determining if sufficient time has passed since the most recent execution of the routine to avoid polarization effects on the measured open circuit voltage;

load test initiating means responsive to insufficient time having passed since the last start, for imposing a load on the vehicle battery by engaging an engine starter system;

sampling means response to passage of a period T after the engine starter system has been engaged, for taking a voltage measurement from the voltage sensor and a current measurement from the battery current sensor;

a specification table indicating battery capacity as a function of the results of a load test;

an engine required cranking power specification using at least ambient temperature as an input; and

a second comparator taking the a capacity figure for the vehicle battery and an engine required cranking power figure obtained from the engine required cranking power specification as inputs and indicating a result for the comparison.

20. Apparatus as claimed in claim 19, further comprising a battery history table including records of the results of each battery test for which the capacity of the vehicle battery exceeded the engine required cranking power figure.

21. Apparatus as claimed in claim 20, further comprising a comparator for taking the open circuit voltage and the allowable open circuit voltage range as inputs and for indicating a need for battery maintenance if the open circuit voltage falls outside the allowable range.

22. Apparatus as claimed in claim 20, wherein battery current sensor is connected to the negative terminal of the battery and to the chassis ground for obtaining a voltage drop across a battery ground wire and determining current from that measurement.

23. Apparatus as claimed in claim 21, further comprising a mathematical function execution block stored in memory responsive to the timer giving a counter indication of possible polarization in the vehicle battery, for determining a proportion of battery state of charge by solution of a second order polynomial equation of the form

24. Apparatus as claimed in claim 23, wherein A>

>

0.3351, B>

>

−

7.0154 and C>

>

36.195.

25. Apparatus as claimed in claim 23 further comprising, means for substituting a solution of the second order polynomial equation as an input to the second comparator for the results of a load test.

26. Apparatus as claimed in claim 25 further comprising, means for saving a record of the results of the battery test in a battery history table responsive to the each start where battery capacity is indicated as exceeding the engine required cranking power figure by the second comparator.

27. Apparatus as claimed in claim 26, wherein the battery history table includes a record for each start and successful test of the vehicle battery, with the records being ordered and each record including the measured open circuit voltage and a state of charge metric.

28. Apparatus as claimed in claim 27, wherein the battery specification table for battery capacity includes battery ratings at ambient temperature correlated with records in the battery history table.

29. Apparatus as claimed in claim 28, further comprising sensors for engine coolant temperature, engine lubricant and a timer tracking time of operation for the engine, and wherein the engine required cranking power specification is addressed using measurements for ambient temperature, coolant temperature and engine lubricant temperature as well as engine time of operation.