Battery life determination

• US 7,285,935 B2
• Filed: 03/08/2004
• Issued: 10/23/2007
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: Fuge, Jonathan P
• Primary Examiner(s): Tso; Edward H
• Application Number:
  US10/793,879
• Publication Number:
  US 20040178771A1
• Time in Patent Office: 1,324 Days
• Field of Search: 320/132, 320/149, 320/DIG.21, 324/426, 324/430, 324/433
• US Class Current: 320/132
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm

Abstract

A method and apparatus are disclosed for providing a battery low voltage warning for a range of batteries having various initial voltages. When a battery is inserted into a battery holder its initial off-load voltage is measured using a microprocessor. The microprocessor selects a suitable voltage threshold, at which the battery is considered to be discharged, from a predetermined number of voltage thresholds. The initial off-load voltage of the battery is used by the microprocessor as a basis for selecting a suitable threshold. An LED warning or the like is used to indicate that the threshold is reached in use. A measurement probe is shown which uses such a method and apparatus.

Claims

1. A method for providing a battery low voltage warning comprising the steps of:

electrically connecting a battery having at least one voltaic cell to a battery holder;

measuring an off-load voltage of the at least one voltaic cell; and

determining a suitable voltage threshold, only from the off-load voltage, at which the at least one voltaic cell is considered to be discharged; and

providing a warning when that threshold is reached.

2. A method for providing a battery low voltage warning as claimed in claim 1 wherein the step of determining a suitable voltage threshold at which the at least one voltaic cell is considered to be discharged includes selecting an appropriate predetermined voltage threshold from a plurality of such voltage thresholds dependent on the measured off-load voltage.

3. A method for providing a battery low voltage warning as claimed in claim 1 wherein the method provides the further step of determining the a state of the at least one voltaic cell by load testing the voltaic cell and measuring the voltaic cell voltage during the load test.

4. A method for providing a battery low voltage warning as claimed in claim 3 wherein the step of determining the state of the at least one voltaic cell includes accepting the battery if a difference in the measured cell voltage and the voltaic cell voltage measured during the load test is less than a predetermined amount.

5. A method for providing a battery low voltage warning as claimed in claim 4 wherein the predetermined amount is about 10%.

6. A method for providing a battery low voltage warning as claimed in claim 4 wherein the step of determining the state of the at least one voltaic cell by load testing the voltaic cell is performed after the step of measuring the off-load voltage of the voltaic cell.

7. A method for providing a battery low voltage warning as claimed in claim 1 employing a microprocessor and an algorithm for carrying out the steps.

8. A method for providing a battery low voltage warning as claimed in claim 7 wherein the method provides the further step of entering a microprocessor programming mode for altering the algorithm if the measured off-load voltage falls within a predetermined range.

9. A method for providing a battery low voltage warning as claimed in claim 1 wherein every time the step of electrically connecting a battery to a battery holder is carried out, the other steps of claim 1 are repeated.

10. Apparatus for providing a battery low voltage warning comprising:

a battery holder into which a battery is insertable, the battery comprising at least one voltaic cell;

a voltage measuring device electrically connected to the at least one voltaic cell when the battery is inserted in the holder, and providing a measure of the off-load voltage of the at least one voltaic cell;

a device determining the suitable voltage threshold at which the at least one voltaic cell is considered to be discharged, dependent only on the off-load voltage measured by the voltage measuring device; and

a warning device providing a warning when that threshold is reached.

11. Apparatus for providing a battery low voltage warning as claimed in claim 10 wherein the device for determining a suitable voltage threshold selects an appropriate predetermined voltage threshold from a plurality of such voltage thresholds dependent on the measured off-load voltage.

12. Apparatus for providing a battery low voltage warning as claimed in claim 10 further comprising:

a load testing device which measures the voltage of the at least one voltaic cell when the voltaic cell is subjected to an electrical load.

13. Apparatus for providing a battery low voltage warning as claimed in claim 12 wherein the load testing device is operative such that the battery is accepted if a difference in the measured voltage of the at least one voltaic cell and the at least one voltaic cell voltage measured during the load test is less than a predetermined amount.

14. Apparatus for providing a battery low voltage warning as claimed in claim 13 wherein the predetermined amount is about 10%.

15. Apparatus for providing a battery low voltage warning as claimed in claim 10 wherein the voltage measuring device providing a measure of the off-load voltage of the at least one voltaic cell, the device determining a suitable voltage threshold at which the at least one voltaic cell is considered to be discharged, and the load testing device comprise a microprocessor having an algorithm performing the function of the said devices.

16. Apparatus for providing a battery low voltage warning as claimed in claim 15 wherein the algorithm is reprogrammable when the off-load voltage is measured to be within a predetermined range.

17. A measurement probe having apparatus for providing a battery low voltage warning comprising:

a battery holder into which a battery is insertable, the battery comprising at least one voltaic cell;

a voltage measuring device electrically connected to the at least one voltaic cell when the battery is inserted in the holder, and providing a measure of the off-load voltage of the at least one voltaic cell;

a device determining a suitable voltage threshold at which the at least one voltaic cell is considered to be discharged, dependent only on the off-load voltage measured by the voltage measuring device; and

a warning device providing a warning when that the suitable voltage threshold is reached.