Condition monitoring of opportunity charged batteries

• US 6,380,716 B1
• Filed: 11/17/2000
• Issued: 04/30/2002
• Est. Priority Date: 11/17/2000
• Status: Expired due to Term

• Current Assignee: Curtis Instruments Incorporated
• Original Assignee: Curtis Instruments Incorporated
• Inventors: Finger, Eugene P.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US09/716,121
• Time in Patent Office: 529 Days
• Field of Search: 320/131, 320/130, 320/136, 320/DIG.21, 324/433, 324/426
• US Class Current: 320/131
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]

Abstract

In a preferred embodiment, a method of condition monitoring of an opportunity charged battery, including: determining length of time the battery has been off-line; determining whether charging of the battery has occurred during the length of time; if step (b) results in a determination that the charging of the battery has occurred, determining degree of charging of the battery occurring during the length of time; and if step (b) results in a determination that charging of the battery has occurred, resetting a condition monitor associated with the battery to reflect the degree of charging of the battery.

Claims

1. A method of condition monitoring of an opportunity charged battery, comprising:

(a) determining length of time said battery has been off-line;

(b) determining whether charging of said battery has occurred during said length of time;

(c) if step (b) results in a determination that said charging of said battery has occurred, determining degree of charging of said battery occurring during said length of time; and

(d) if step (b) results in a determination that charging of said battery has occurred, resetting a condition monitor associated with said battery to reflect said degree of charging of said battery.

2. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

step (b) includes measuring terminal voltage of said battery at time of putting said battery on-line and comparing said terminal voltage of said battery at time of putting said battery on-line with a predetermined value which indicates that charging has occurred during said length of time.

3. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

step (b) includes;

(e) computing a state-of-charge of said battery at time of putting said battery off-line and determining an expected voltage threshold at time of putting said battery on-line from said computed state-of-charge;

(f) measuring actual voltage threshold upon putting said battery on-line; and

(g) comparing said expected voltage threshold with said actual voltage threshold.

4. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

steps (b) and (c) include;

(e) combining data representing charging current versus time and coulombic efficiency versus time for said battery to produce a transform of true state-of-charge versus time;

(f) computing state-of-charge at time said battery is taken off-line;

(g) using said state-of-charge at time said battery is taken off-line to extract a first value of time from said transform;

(h) adding said first value of time and said length of time to produce a second value of time; and

(i) using said second value of time to extract a value from said transform representing said degree of charging of said battery.

5. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

steps (b) and (c) include;

(e) computing a state-of-charge of said battery based upon a measurement of dV/dt at time of putting said battery on-line;

(f) computing a state-of-charge of said battery based upon a thermal analysis of said battery at said time of putting said battery on-line;

(g) computing a state-of-charge based on absolute battery voltage at time of putting said battery on-line; and

(h) averaging values obtained in steps (e), (f), and (g) to obtain an estimate of true state-of-charge and said degree of charging of said battery.

6. A method of condition monitoring of an opportunity charged battery, as defined in claim 5, wherein:

said true state-of-charge is not permitted to exceed an upper bound.

7. A method of condition monitoring of an opportunity charged battery, as defined in claim 5, wherein:

said true state-of-charge is not permitted to descend below a lower bound.

8. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

steps (b) and (c) include;

(e) computing VD versus time, where VD is open circuit voltage of said battery which is descending from a previous charge at time of taking said battery off-line, where said battery had been charged, was disconnected from a charger, reconnected to a load and battery monitor, not used, and was taken off-line at the moment of VD measurement;

(f) computing VD′

versus time, where VD′

is terminal voltage at time of taking said battery off-line when said battery is recovering from discharge activity;

(g) computing VS, where VS is voltage at which said battery will reasonably stabilize over a long period of time;

(h) recording voltage (VD or VD′

) at time of taking said battery off-line;

(i) recording computed state-of-charge (SD) at time of taking said battery off-line;

(j) recording real time at time of taking said battery off-line;

(k) recording voltage (VR or VR′

) at time of putting said battery on-line;

(l) recording real time at time of putting said battery on-line;

(m) computing VS based upon SD;

(n) computing said length of time;

(o) determining last charge or discharge by determining whether VD is higher than VS or VD′

lower than VS;

(p) computing anticipated VR or VR′

;

(q) determining if actual VR or VR′

is higher than anticipated VR or VR′

; and

(r) if actual VR or VR′

is higher than anticipated VR or VR′

, then determining whether charging took place near term or some time ago.

9. A method of condition monitoring of an opportunity charged battery, as defined in claim 8, wherein:

determining whether charging took place near term or some time ago is accomplished using dV/dt analysis.

10. A method of condition monitoring of an opportunity charged battery, as defined in claim 8, wherein:

determining whether charging took place near term or some time ago is accomplished using differential thermal analysis.

11. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

step (d) includes running said condition monitor at a high rate during an adaptation, process.

12. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

step (b) includes measuring specific gravity of electrolyte of said battery at time of putting said battery on-line and comparing said specific gravity of electrolyte of said battery at time of putting said battery on-line with a predetermined value which indicates that charging has occurred during said length of time.

13. A method of condition monitoring of an opportunity charged battery, as defined in claim 1, wherein:

step (b) includes;

(e) computing a state-of-charge of said battery at time of putting said battery off-line and determining an expected specific gravity of electrolyte of said battery at time of putting said battery on-line from said computed state-of-charge;

(f) measuring actual specific gravity of electrolyte of said battery upon putting said battery on-line; and

(g) comparing said specific gravity of electrolyte of said battery with said actual specific gravity of electrolyte of said battery.

14. An apparatus for monitoring condition of an opportunity charged battery, comprising:

(a) means to determine length of time said battery has been off-line;

(b) means, connected to means of element (a), to determine whether charging of said battery has occurred during said length of time;

(c) means, connected to means of element (b), to determine if step (b) results in a determination that said charging of said battery has occurred and, if so, to determine degree of charging of said battery occurring during said length of time; and

(d) means, connected to means of element (b), to determine if step (b) results in a determination that charging of said battery has occurred and, if so, to reset a condition monitor associated with said battery to reflect said degree of charging of