Networked battery monitor and control system and charging method

• US 5,666,040 A
• Filed: 08/27/1996
• Issued: 09/09/1997
• Est. Priority Date: 08/27/1996
• Status: Expired due to Fees

• Current Assignee: Frank Bourbeau
• Original Assignee: Frank Bourbeau
• Inventors: Bourbeau, Frank
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US08/704,226
• Time in Patent Office: 378 Days
• Field of Search: 320/6, 320/7, 320/15, 320/16, 320/18, 320/30, 320/32, 320/35, 320/39, 320/48, 320/46
• US Class Current: 320/118
• CPC Class Codes: B60L 2210/30 AC to DC converters
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A safe, low-cost battery monitor and control system is presented. Electronic modules are connected to the terminals of respective batteries that make up a series string. Each module produces a go/no-go signal for each of four battery conditions: over-voltage, under-voltage, over-temperature and float-voltage, which are read by a network controller connected to each module via a single three-wire local area network. Based on the information received, the controller can adjust the charging current to the string, terminate the charge cycle, limit the current drawn from the string when in use, or disconnect the string from the system it is powering. The controller can record a history of the charge and discharge activity of each battery, so that the weakest batteries can be identified and replaced instead of scrapping the entire string. The system controls the charging current delivered to each battery during a charge cycle to insure that each battery is neither overcharged nor undercharged, by connecting a bypass circuit across the battery'"'"'s terminals to reduce the charging current when an over-voltage condition is detected, or by reducing charge current to the string. A battery'"'"'s voltage measurement is temperature compensated so that it can be accurately compared to temperature dependant limits. The addressable switch is bidirectional, so that the controller can, for example, force bypass resistors to be connected across selected batteries in order to heat up the batteries in a cold environment.

Claims

1. A networked battery monitor and control system, comprising:

monitor circuitry to compare at least one parameter of each battery in a group of batteries with predetermined limits, said monitor circuitry producing go/no-go signals with respect to each of said limits,

bypass circuitry responsive to said monitor circuitry and connectable across the terminals of individual batteries when their respective battery voltages exceed respective predetermined limits, to reduce the amount of charging current flowing through them,

a controller that receives said go/no-go signals and reduces the charging current to a group of batteries when said bypass circuitry is unable to reduce the voltage of a battery in the group below a predetermined limit, said controller located remote from said monitor circuitry, and

cabling interconnecting said monitor circuitry and said remote controller for carrying said go/no-go signals between them.

2. The system of claim 1, further comprising a local area network (LAN) for conveying said go/no-go signals to said controller.

3. A networked battery monitor and control system, comprising:

a plurality of modules, each of said modules connectable to the terminals of a respective battery that is one of a series string of batteries, said modules each comprising;

monitor circuitry to compare at least one parameter of a respective battery with predetermined limits, said circuitry producing a go/no-go signal with respect to each of said limits,

a bypass circuit connectable across the terminals of a battery to reduce charging current to the battery,

bypass control circuitry responsive to said monitor circuitry to connect said bypass circuit across the terminals of a battery when the battery'"'"'s voltage exceeds a predetermined limit, and

at least one addressable switch, said switch connectable to a local area network, said switch making said go/no-go signals available to said network when addressed,

a local area network cable, said cable connected to each of said addressable switches, and

a network controller connected to said cable, said controller addressing each of said switches in turn and determining the state of said go/no-go signals, said controller programmed to control the charging and discharging of a series string of batteries based on the states of said signals.

4. The system of claim 3, further comprising a plurality of temperature sensors connectable to a terminal of a respective battery, each sensor providing an output that varies with temperature to said monitor circuitry in respective modules.

5. The system of claim 3, wherein said monitor circuitry monitors a respective battery for over-temperature, over-voltage, under-voltage, and float-voltage conditions.

6. The system of claim 3, wherein each of said modules is in close physical contact with the terminals of a respective battery such that no separate insulated conductors are required to interface to said battery.

7. The system of claim 3, further comprising a battery pack charger connectable to a series string of batteries, said charger controllable by said network controller.

8. The system of claim 3, wherein said network controller causes a battery pack charger connected across a series string of batteries to reduce the charging current to the string if the voltage of a battery in the string does not fall below a predetermined limit when said bypass circuit is connected across the battery'"'"'s terminals.

9. The system of claim 3, wherein said bypass circuit includes a bypass resistor.

10. The system of claim 9, wherein said bypass resistor is a distributed resistor made from a circuit board trace.

11. The system of claim 3, wherein said bypass circuit includes a DC to DC converter having inputs connectable across a respective battery'"'"'s terminals and having outputs connectable to the top and bottom of a string of batteries.

12. The system of claim 3, further comprising at least one hydrogen detector located within a compartment holding a series string of batteries, said detector causing the string to be disconnected from said system when a predetermined hydrogen concentration limit is exceeded in said compartment.

13. The system of claim 3, further comprising at least one temperature sensor located within a compartment holding a series string of batteries, said sensor causing the string to be disconnected from said system when a predetermined temperature limit is exceeded in said compartment.

14. The system of claim 3, further comprising a discharge controller connected to a series string of batteries to control the discharge of the string, said discharge controller controllable by said network controller.

15. The system of claim 14, wherein said discharge controller is a traction inverter.

16. The system of claim 3, further comprising a contactor connectable in series with a series string of batteries, to connect and disconnect the string to and from said system.

17. The system of claim 3, wherein said string is disconnected from said system when all batteries in said string are fully charged.

18. The system of claim 3, wherein said switches are bidirectional such that said network controller can command an action to occur on a module by addressing and writing to a switch on said module.

19. The system of claim 18, wherein said action comprises connecting said bypass circuit across the terminals of a battery to cause heat to be generated.

20. The system of claim 3, wherein said monitor circuitry comprises a microprocessor suitable for performing said comparisons between said battery parameters and said predetermined limits, producing said go/no-go signals, and providing system timing functions.

21. A networked battery monitor and control system, comprising:

a plurality of batteries connected in series to form a series string,

a plurality of modules, each of said modules connectable to the terminals of a respective one of said batteries, said modules each comprising;

monitor circuitry to compare at least one parameter of the module'"'"'s respective battery with predetermined limits, said circuitry producing a go/no-go signal with respect to each of said limits,

a bypass circuit connectable across the terminals of the module'"'"'s respective battery to reduce charging current to the battery,

bypass control circuitry responsive to said monitor circuitry to connect said bypass circuit across the terminals of the module'"'"'s respective battery when the battery'"'"'s voltage exceeds a predetermined limit, and

at least one addressable switch, said switch connectable to a local area network, said switch making said go/no-go signals available to said network when addressed,

a local area network cable, said cable connected to each of said addressable switches, and

a network controller connected to said cable, said controller addressing each of said switches in turn and determining the state of said go/no-go signals, said controller programmed to control the charging and discharging of said series string of batteries based on the states of said signals.

22. The system of claim 21, wherein said system includes four series strings of 28 batteries, said strings connected in parallel.

23. A networked battery monitor and control system, comprising:

a plurality of modules, each of said modules connectable to the terminals of a respective battery that is one of a series string of batteries, said modules each comprising;

monitor circuitry to compare at least one parameter of a respective battery with predetermined limits, said circuitry producing a go/no-go signal with respect to each of said limits,

and

at least one addressable communication device, said device making said go/no-go signals available to a controller when addressed,

a controller that addresses each of said devices and determines the state of said go/no-go signals, said controller reducing charging current to a series string of batteries when the voltage of a battery in the string exceeds a predetermined limit, said controller located remote from said monitor circuitry, and

cabling interconnecting said monitor circuitry and said remote controller for carrying said go/no-go signal between them.

24. The system of claim 23, further comprising bypass circuitry responsive to said monitor circuitry and connectable across the terminals of individual batteries when their respective battery voltages exceed one of said predetermined limits, to reduce the amount of charging current flowing into them.

25. A battery monitor and control module, comprising:

a plurality of comparators suitable for connection to a battery to compare the voltage and temperature of a battery with predetermined limits and to change the logic state of respective outputs if said limits are exceeded,

a voltage reference for supplying threshold voltages to each of said comparators, said threshold voltages representing different respective predetermined limits,

a bypass circuit connectable to the terminals of a battery to reduce charging current to the battery when the battery'"'"'s voltage exceeds an over-voltage limit, and

at least one communication device, said at least one device connected to receive a combination of said comparator outputs at respective inputs and having respective outputs that assume the state of said respective inputs when said device is interrogated.

26. The module of claim 25, wherein said comparators include an over-voltage limit comparator, an under-voltage limit comparator, an over-temperature limit comparator, and a float-voltage limit comparator.

30. The module of claim 25, wherein said bypass circuit comprises a resistor.

31. The module of claim 30, wherein said resistor is formed from a circuit board trace.

32. The module of claim 25, wherein said bypass circuit comprises a DC to DC converter having inputs that are connectable across a battery'"'"'s terminals and outputs connectable to the top and bottom of a series string of batteries.

35. The module of claim 25, further comprising a temperature sensor suitable for attachment to a battery and producing an output that varies in accordance with the battery'"'"'s temperature, said module receiving and using said sensor output to bias a voltage received from the battery as a function of the battery'"'"'s temperature, said biased voltage being used for comparison with said predetermined limits.

36. The module of claim 25, further comprising a battery connected to said module, said module comparing parameters of said battery with said predetermined limits and to change the logic state of respective outputs when said limits are exceeded and making said outputs available for interrogation through said communication devices.

37. The module of claim 36, wherein said module is mounted to said battery such that the terminals of said battery are directly connectable to said module without intervening insulated conductors.

27. A battery monitor and control module, comprising:

a plurality of comparators suitable for connection to a battery to compare the voltage and temperature of a battery with predetermined limits and to change the logic state of respective outputs if said limits are exceeded,

a voltage reference for supplying threshold voltages to each of said comparators, said threshold voltages representing different respective predetermined limits,

a bypass circuit connectable to the terminals of a battery to reduce charging current to the battery when the battery'"'"'s voltage exceeds an over-voltage limit, and

at least one communication device, said at least one device connected to receive a combination of said comparator outputs at respective inputs and having respective outputs that assume the state of said respective inputs when said device is interrogated, wherein said communication devices are addressable switches.

28. A battery monitor and control module, comprising:

a plurality of comparators suitable for connection to a battery to compare the voltage and temperature of a battery with predetermined limits and to change the logic state of respective outputs if said limits are exceeded,

a voltage reference for supplying threshold voltages to each of said comparators, said threshold voltages representing different respective predetermined limits,

a bypass circuit connectable to the terminals of a battery to reduce charging current to the battery when the battery'"'"'s voltage exceeds an over-voltage limit, and

at least one communication device, said at least one device connected to receive a combination of said comparator outputs at respective inputs and having respective outputs that assume the state of said respective inputs when said device is interrogated, wherein said communication devices comprise a single one-bit addressable switch.

29. A battery monitor and control module, comprising:

a plurality of comparators suitable for connection to a battery to compare the voltage and temperature of a battery with predetermined limits and to change the logic state of respective outputs if said limits are exceeded,

a voltage reference for supplying threshold voltages to each of said comparators, said threshold voltages representing different respective predetermined limits,

a bypass circuit connectable to the terminals of a battery to reduce charging current to the battery when the battery'"'"'s voltage exceeds an over-voltage limit,

at least one communication device, said at least one device connected to receive a combination of said comparator outputs at respective inputs and having respective outputs that assume the state of said respective inputs when said device is interrogated, and

a timing circuit that connects said bypass circuit across a battery'"'"'s terminals for a predetermined amount of time to reduce charge current to the battery.

33. A battery monitor and control module, comprising:

a plurality of comparators suitable for connection to a battery to compare the voltage and temperature of a battery with predetermined limits and to change the logic state of respective outputs if said limits are exceeded,

a voltage reference for supplying threshold voltages to each of said comparators, said threshold voltages representing different respective predetermined limits,

a bypass circuit connectable to the terminals of a battery to reduce charging current to the battery when the battery'"'"'s voltage exceeds an over-voltage limit,

at least one communication device, said at least one device connected to receive a combination of said comparator outputs at respective inputs and having respective outputs that assume the state of said respective inputs when said device is interrogated, and

an electrical isolation barrier between said addressable switches and said comparator outputs.

34. The module of claim 33, wherein said electrical isolation barrier is comprised of optocouplers.

38. A method of charging a series string of batteries, comprising the steps of:

applying a predetermined amount of charging current through a string of series-connected batteries,

monitoring the voltage of each battery making up said series string,

bypassing a portion of said charging current around any individual battery in the string whose voltage exceeds an over-voltage limit,

reducing the charging current through said string if the voltage of any battery that is exceeding said over-voltage limit does not fall below said limit after a predetermined amount of time, the value of said reduced charging current being greater than zero,

terminating said charging current through said string when the voltage of each battery making up said string exceeds a predetermined limit.

39. The method of claim 38, wherein said bypassing of charging current around an individual battery is accomplished by switching a bypass resistor across the terminals of said battery.