US 5,773,962 A · Battery energy monitoring circuits

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.

Claims15

Dependent claims

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.

6 more elements

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.

7 more elements

Dependencies are inferred from the claim text.

Battery energy monitoring circuits

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Battery energy monitoring circuits

Life of this patent

Abstract

Claims15