Device for predicting imminent failure of a stationary lead acid battery in a float mode

• US 5,250,904 A
• Filed: 12/16/1992
• Issued: 10/05/1993
• Est. Priority Date: 08/08/1991
• Status: Expired due to Fees

• Current Assignee: Advanced Power Technology Incorporated (Microchip Technology Incorporated)
• Original Assignee: Advanced Power Technology Incorporated (Microchip Technology Incorporated)
• Inventors: Salander, Arthur B., Fortner, Douglas C.
• Primary Examiner(s): Strecker, Gerard R.
• Assistant Examiner(s): DO, DIEP N
• Application Number:
  US07/991,481
• Time in Patent Office: 293 Days
• Field of Search: 324/426, 324/430, 324/431, 324/433, 324/434, 324/435, 340/636, 320/48
• US Class Current: 324/430
• CPC Class Codes: G01R 31/3646 for indicating electrical conditions or variables, e.g. visual or audible indicators
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G01R 31/388 involving voltage measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]

Abstract

A stationary battery testing device as provided for measuring imminent battery failure while the battery is in a float mode. The device includes a circuitry for measuring the internal resistance changes of a battery and then comparing them over a predetermined duration of time so as to provide audible or visual discernable signals to indicate an imminent battery failure after the expiration of said predetermined period of time. An additional temperature monitoring component may be provided for the device to monitor internal changes within the battery with respect to temperature. This can also be combined in a temperature compensated automatic adjustment of voltage and alarm thresholds in an active feedback loop to augment and broaden the basis of stationary battery applications where the battery testing device can be used.

Claims

1. A device for predicting an imminent failure of a stationary lead acid battery/cell comprising a means for monitoring a first predetermined upper voltage limit of said battery/cell and a means for monitoring a predetermined lower limit thereof in a float mode, said float mode comprising a condition in which said battery/cell'"'"'s voltage level is in an electrical equilibrium, being neither substantially electrically charged nor substantially electrically drained in the float mode, said float mode comprising;

a) a float voltage level, said float voltage level being intermediate between said upper voltage limit and said lower voltage limit, the device further comprising;

(b) a current limit battery charger maintaining said voltage level across said battery/cell, said current limiting battery charger causing and maintaining said battery float mode;

(c) said means for monitoring a predetermined upper voltage limit, said means for monitoring a predetermined lower voltage limit and said means for monitoring a float voltage level producing respective output signals, said output signals being fed up to a comparator means;

d) said comparator means being for comparing said float voltage output signals with said predetermined upper voltage limit and said lower voltage limit, said comparator means generating an alarm output signal as required, said upper and lower voltage limits serving as reference values, said comparator means further being capable of delivering discernable output signals in response to input of said predetermined float voltage level across said battery/cell;

e) said discernable comparator output signals being indicative of changes in said float voltage level of said battery/cell and,

f) means for warning a user of an imminent failure of said battery/cell, said warning means comprising a first transistor and alarm means for generating an alarm signal perceivable by said user, said first transistor capable of energizing said warning means and said first transistor responsive to said discernable comparator output signals and, said first transistor capable of energizing said alarm means for warning a user of imminent battery failure of said battery/cell, said device further having

g) a time measurement means for measuring a predetermined interval, said time measurement means providing output signals capable of being fed to said comparator means, said time interval measurements being critical to the operation of said comparator means;

h) said comparator means requiring a predetermined time interval for determining when to generate an alarm output change as required, said alarm signal output being required when said comparator means has detected a battery/cell float voltage level which has exceeded said predetermined upper voltage limit or said predetermined lower voltage limit for a time period exceeding said predetermined time interval and further;

i) said comparator means being capable of delaying an alarm response until an expiration of said predetermined time interval.

2. The device as in claim 1 wherein said device is further provided with a means to isolate and control float voltage monitor signals means, said means to isolate and control said voltage monitor output signals comprises a voltage regulator, said voltage regulator being capable of isolating and controlling said float voltage monitor signals being fed into said comparator means, further wherein:

said comparator means comprises a comparator, circuit having a resistor ladder circuit therein;

said resistor ladder being a circuit capable of causing input signals to be discernable to deliver said output signals.

3. The device as in claim 1, further comprising a second transistor and an optically isolated sensing means capable of exciting said second transistor, and a battery failure alarm relay, wherein said second transistor is responsive to energizing said battery failure alarm relay, which said relay in turn, energizes said alarm means to produce a sensible alarm indicating imminent battery failure.

4. The device as in claim 3 wherein said optically isolated sensing means comprises an opto-isolator array with Darlington transistors driving said battery failure alarm relay.

5. The device as in claim 1, further comprising a temperature indicating means, said temperature indicating means being responsive to monitoring ambient temperature and temperature of single cells within a monitored battery/cell.

6. The device as in claim 5 wherein said temperature indicating means is capable of providing alarm signals in response to both high and low measured temperatures, said temperature indicating means further providing a remote temperature indication output.

7. The device as in claim 1, further comprising an automatic feedback control loop having a temperature-controlled alarm threshold, said loop capable of measuring said first predetermined upper limit of a voltage level and said second predetermined lower limit of a voltage level.

8. The device as in claim 2 wherein said voltage regulator has a preset input voltage, said voltage regulator capable of regulating said float voltage monitor signals emanating from said battery/cell in a float mode;

said float voltage monitor signals being fed to said comparator, said comparator further being capable of evaluating a predetermined deviating fluctuation pattern of voltage monitor signals in comparison to expected norms for said fluctuations of voltage in a monitored battery/cell and further wherein;

a) said resistor ladder circuit capable of receiving said float voltage monitor signals emanating from said battery/cell in a float mode, said resistor ladder circuit causing said fed voltage monitor signals to be incrementally transmitted as said voltage value of said fed float voltage monitor signals fluctuates; and

b) said comparator being capable of converting analog signals to digital signals, said digital signals in turn being indicative of a voltage greater than zero or a voltage of zero.

9. The device as in claim 3 wherein said battery failure alarm relay comprises a timing relay, said timing relay being capable of indicating imminent battery failure after a predetermined time interval.

10. A battery-life indicator that predicts failure of a stationary battery/cell within a predetermined minimum warning time period before occurrence of actual battery/cell failure, comprising:

a) a sensing means for sensing a change in the internal resistance of a battery/cell, said sensing means including a monitoring means to monitor a float voltage across a battery/cell, said monitoring means being responsive to changes in said float voltage;

b) indicating means for indicating changes in said float voltage of a battery/cell, and further for indicating whether the fluctuations in battery/cell float voltage represent a change in said battery/cell'"'"'s internal resistance, further

c) said monitoring means being responsive to changes in an internal structure of said battery/cell;

d) said monitoring means further including a plurality of resistors and a comparator, said monitoring means receiving and continuously comparing said monitored battery/cell float voltage level to predetermined upper or lower normative values within a normative range, said normative float voltage range being comprised of a range of voltage values between said upper and lower float normative voltage levels, said comparators being capable of operating an alarm signal indicating that said battery/cell float voltage exceeds said normative float voltage range of said float voltage window;

e) a series of visual indicator means responsive to said comparator, said series of visual indicators for providing a visual indication of an instant battery float voltage level as compared to said normative float voltage range.

11. The battery life indicator of claim 10 further comprising:

a) at least one transistor;

b) at least one opto-isolator capable of exciting said, at least one transistor,

c) one or more battery/cell failure alarm relays capable of providing a time delay, wherein

d) said at least one transistor is responsive to an excitation of said at least one transistor provided by said at least one opto-isolator by energizing said one or more battery/cell failure alarm relays, which said relays after a time delay, and in response to a battery/cell float voltage deviation outside of a float voltage window of normative values for a period of time greater than a preset temporal interval, energize said alarm means to produce a sensible alarm indication of imminent battery/cell failure.

12. The battery life indicator as in claim 11 wherein said one or more battery failure alarm relays further comprises an alarm circuit including a flashing light emitting diode, an audible signal, and a digital output, all of which are activated by a required activating input from said one or more time delay relay.

13. The battery life indicator as in claim 12, further comprising a temperature measurement module for indicating ambient, single battery/cell and single cell temperature, the ambient temperature measurement further providing a feedback signal to said battery life indicator to compensate for shifts in ambient temperature which could affect the accuracy of said battery/cell life indicator, the temperature measurement module further comprising a temperature alarm system providing audible, visual, electronic and switching indications of predetermined high or low temperature events.