Battery life determination

• US 20040178771A1
• Filed: 03/08/2004
• Published: 09/16/2004
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: Fuge, Jonathan P.
• Granted Patent: US 7,285,935 B2
• Time in Patent Office: Days
• US Class Current: 320/136
• 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 the initial off-load voltage of the at least one voltaic cell; and

determining a suitable voltage threshold at which the at least one cell is considered to be discharged, dependent on the initial off-load voltage; 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 cell is considered to be discharged includes selecting an appropriate predetermined voltage threshold from a plurality of such voltage thresholds dependent on the measured initial 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 initial state of the at least one cell by load testing the cell and measuring the 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 initial state of the at least one cell includes accepting the battery if the difference in the measured initial cell voltage and the 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 initial state of the at least one cell by load testing the cell is performed after the step of measuring the off-load voltage of the 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 initial 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 initial off-load voltage of the at least one voltaic cell;

a device determining the suitable voltage threshold at which the at least one cell is considered to be discharged, dependent 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 initial 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 cell when the 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 the difference in the measured initial voltage of the at least one cell and the at least one 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 initial off-load voltage of the at least one voltaic cell, the device determining a suitable voltage threshold at which the at least one 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 initial 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 initial off-load voltage of the at least one voltaic cell;

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

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