Battery energy monitoring circuits

• US 5,773,962 A
• Filed: 04/22/1997
• Issued: 06/30/1998
• Est. Priority Date: 01/17/1995
• Status: Expired due to Term

• Current Assignee: Minit Charger, LLC
• Original Assignee: Norvik Traction, Inc.
• Inventors: Nor, Jiri K.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): SHIN, KYUNG E
• Application Number:
  US08/841,455
• Time in Patent Office: 434 Days
• Field of Search: 320/134, 320/119, 320/116, 320/122
• US Class Current: 320/134
• CPC Class Codes: B60L 2240/36 Temperature of vehicle components or parts
• CPC Class Codes: B60L 2250/10 by alarm
• CPC Class Codes: B60L 2250/16 by display
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: B60L 3/0092 with use of redundant elements for safety purposes
• CPC Class Codes: B60L 50/20 using propulsion power generated by humans or animals
• CPC Class Codes: B60L 53/11 DC charging controlled by the charging station, e.g. mode 4
• CPC Class Codes: B60L 58/13 Maintaining the SoC within a determined range
• CPC Class Codes: B60L 58/14 Preventing excessive discharging
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/18 of two or more battery modules
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: B60L 58/26 by cooling
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0016 : using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0031 : using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0048 : Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/02 : for charging batteries from ac mains by converters
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 : Electric charging stations
• CPC Class Codes: Y02T 90/14 : Plug-in electric vehicles
• CPC Class Codes: Y02T 90/16 : Information or communication technologies improving the operation of electric vehicles

Abstract

A long chain battery, particularly for an electric vehicle, comprises a plurality of series connected cells or battery modules. To control the operation of the electrical functions, including discharge while the vehicle is being driven, charging when it is at a charging station, or regenerative charging during braking, a main control module and a plurality of battery monitoring modules are provided. The electric motor and a traction controller therefor are connected in series across the long chain battery, and other vehicle electrical loads are in parallel with the motor and controller. Each battery monitoring module will monitor a number of batteries, and the current carrying wire between them, so that incipient problems may be detected before failure or significant damage occurs. A serial communications bus is provided between the main control module and the battery monitoring modules, and data transmitted over that bus is generally digitally encoded. Sensitive analog circuitry in the battery monitoring modules is located in proximity to the battery modules with which it is associated, and is galvanically isolated from the digital communication circuitry and the data communications bus transmitting the data to the main control module. Any switching or other controllers in the battery are galvanically isolated from the battery monitoring modules and the main control module. Means are provided to isolate specific cells or battery modules, as required; other means are provided to ensure that important voltage and/or current samplings are indicative of equilibrium of the electrical charge or discharge reactions, so that erroneous readings taken during fast acceleration or braking, or other circumstances except essentially steady state conditions, may be discarded. Other means are provided whereby the driver of an electric vehicle receives warnings as the available energy still within the battery depletes below specified levels; and further means are provided to ensure that rate of discharge or regenerative charging of the battery do not exceed predetermined limits.

Claims

1. A monitoring and control apparatus for a battery which comprises a long chain of series connected cells or battery modules, said monitoring and control apparatus being a circuit comprising:

a main control module having a plurality of input and output ports;

at least one battery monitoring module associated with a respective plurality of cells or battery modules, and having input and output communications with said main control module; and

a current sensor means in series with said long chain battery, and having a sensed current input to said main control module;

wherein said main control module includes current control means, current flow interruption means for controlling external means or circuits used for periodically interrupting or changing the current flow in said long chain battery, voltage reading means for receiving and storing voltage information from each of said battery monitoring modules when said current flow has been periodically interrupted or changed, timing means, microprocessor means, annunciator means, battery monitoring module control means, temperature monitoring means, and serial communications bus means;

wherein each of said battery monitoring modules includes serial communications bus means, and data acquisition circuitry which comprises cell or battery voltage monitoring means for each cell or battery module with which it is associated, and control means for controlling switches that are within or series connected with each of said cells or battery modules;

wherein said main control module and said battery monitoring modules are in communication with one another over said serial communications bus means; and

wherein said data acquisition circuitry in each of said battery monitoring modules is galvanically connected with the respective cells or battery modules with which it is associated, and galvanically isolated from said serial communications bus means.

2. The apparatus of claim 1, when installed in an electric vehicle together with said battery;

wherein said main control module further includes a vehicle communication bus which provides control, monitoring, and feedback communications to and from a drive controller in said electric vehicle;

wherein said electric vehicle has an electric motor and a traction controller therefor connected in series across said battery, and other vehicle electrical loads in parallel with said electric motor and traction controller, and a power delivery connector for delivering charging current from a source thereof to said battery;

wherein said drive controller controls said traction controller and said electric motor over said vehicle communication bus; and

wherein terminals and other junctions in said power delivery connector and said electric motor are connected to monitoring means therefor within said respective battery monitoring modules.

3. The apparatus of claim 2, wherein said main control module further includes a charge control interface means to control charging of said battery when it is connected through said power delivery connector to a battery charger, an auxiliary data port as may be required, and at least one or more other auxiliary inputs and outputs as may be required to monitor and control displays and other electrically operating appliances and auxiliary equipment as are located in said electric vehicle;

an input from an external ambient temperature sensor which is mounted in said electric vehicle, and at least one or more other microprocessors and switches as may be required to monitor and control the input, output, or operation of said other electrically operating appliances and auxiliary equipment, and said external ambient temperature sensor.

4. The apparatus of claim 2, wherein each said battery monitoring module further includes at least one or more other auxiliary inputs and outputs as may be required to monitor and control any electrically operating appliances and auxiliary circuits or equipment that are associated with the respective cells or battery modules with which said battery monitoring module is associated;

and

wherein said battery monitoring module further includes one or more additional inputs and outputs as may be required to connect and control any sensors for cell or battery temperature or internal cell or battery pressure or electrolyte level for each individual cell or battery module with which said battery monitoring module is associated.

5. The apparatus of claim 1, wherein data and other transmissions over said serial communications bus means are digitally encoded.

6. The apparatus of claim 4, wherein all battery current carrying wiring which is external to each cell or battery module is, itself, monitored for changes in resistance or voltage which may occur therein by one or more respective battery monitoring modules through a respective input thereto.

7. The apparatus of claim 4, wherein all wiring associated with said cell or battery voltage monitoring means for each cell or battery module with which it is associated is connected to power cable clamps or terminals used to connect battery current wiring to the respective cell or battery module.

8. The apparatus of claim 7, wherein said power delivery connector and said electric motor and traction controller wiring are monitored for changes in resistance or voltage which may occur therein by a respective battery monitoring module through a respective input thereto.

9. The apparatus of claim 1, wherein each cell or battery module in a chain of cells or battery modules associated with each said battery monitoring module has a high current capacity single pole, double throw switch and a bypass current conductor arranged so that one throw of each said switch connects to a first end of said cell or battery module and the other end of said cell or battery module is connected to the common point of the next single pole, double throw switch, and the other throw of each said switch connects to said bypass current conductor and through it also to said common point of said next single pole, double throw switch;

whereby any one or all of said cells or battery modules may be bypassed in said chain; and

whereby, if all cells or battery modules in said chain are bypassed, then the respective other ends or each of said cells or battery modules are all connected to a single bus comprising the series connected bypass conductor, and the respective first ends of each of said cells or battery modules are isolated.

10. The apparatus of claim 9, wherein each of said single pole, double throw switches is a mechanical switch or a solid state, semiconductor switch.

11. The apparatus of claim 10, wherein when said single pole, double throw switch is a solid state, semiconductor switch, said cell or battery module is configured as a two-terminal module having two sides;

wherein one side comprises a cell or battery in series with a parallel connection of a first semiconductor switch and a free wheeling diode which is forward facing with respect to the polarity of said cell or battery and the flow of charging current,

wherein the other side comprises a bypass current conductor in series with a parallel connection of a second semiconductor switch and a rearward facing, with respect to the polarity of said cell or battery, free wheeling diode; and

wherein interlock control means are included in said respective battery monitoring module to preclude a situation where both of said first and second semiconductor switches is permitted to be in their conductive states at the same time.

12. The apparatus of claim 1, wherein the galvanic isolation is by optocouplers.

13. The apparatus of claim 10, wherein said switch is a MOSFET or an IGBT semiconductor switch.

14. The apparatus of claim 12, wherein said switch is a MOSFET or an IGBT semiconductor switch.

15. A method of controlling the rate of charge or discharge current of a long chain battery during discharge or regenerative charging thereof, when said long chain battery is installed in an electric vehicle together with a monitoring and control apparatus therefore;

wherein said long chain battery comprises a plurality of series connected cells or battery modules;

wherein said electric vehicle has installed therein a main control module, at least two battery monitoring modules each associated with a respective plurality of cells or battery modules, a current sensor means in series with said long chain battery, a vehicle communication bus, a drive controller, an electric motor and a traction controller therefor in series across said battery, other vehicle electrical loads in parallel with said series connected electric motor and traction controller, current control means and current flow interruption means within said main control module, a serial communications bus, and voltage reading means for receiving and storing voltage information for each cell or battery module from each of said battery monitoring modules, when said current flow has been periodically interrupted or changed;

wherein said method comprises the steps of;

(a) determining the characteristic charge acceptance curve and discharge ability curve, each being a plot of battery current related to state of charge of said long chain battery, determining a maximum discharge current allowable for said long chain battery, and determining a maximum permitted regenerative charging current due to regenerative braking of said electric vehicle;

(b) during discharge of said long chain battery, limiting the discharge current to no greater than said maximum allowable discharge current;

continuously monitoring said discharge current and the state of charge of said battery; and

when said discharge current and state of charge of said battery reach a point which is indicative of an intersection of said discharge current with said discharge ability curve, activating an annunciation of that fact and controlling the discharge current so that it does not exceed the permitted value of discharge current for any state of charge of said battery; and

when said discharge current falls below a predetermined limit, initiating a controlled stoppage of said electric motor by controlling said traction controller therefor, and causing disconnection of said other electrical loads as necessary; and

(c) during regenerative charging of said long chain battery, limiting regenerative charging current to no greater than said maximum allowable regenerative charging current, continuously monitoring said regenerative charging current and the state of charge of said battery, and when said state of charge of said battery approaches a predetermined level less than the point at which said charge acceptance curve would be intercepted by said maximum regenerative charging current, controlling said regenerative charging current so as to always be below said charge acceptance curve as said state of charge increases.