Shunt resistance device for monitoring battery state of charge

DETAILED DESCRIPTION What is needed therefore, is a device that minimizes the length of the conductors that connect the shunt resistor to the current monitoring unit, thereby reducing the effect of EMI and enabling the current monitoring unit to obtain accurate current measurements for the determination of the state of charge of the battery system.
The present invention is directed to a shunt for use in monitoring the charge and discharge currents in a battery system of a high current system such as automotive Starting, Lighting and Ignition (SLI) systems, electric vehicles, hybrid electric vehicles and Stationary Backup Power (UPS) systems.
A current measurement device in the form of a hybrid circuit on a printed circuit board is mounted directly on the shunt and is electrically connected to the shunt at at least two points.
The portion of the shunt between the at least two points forms the shunt resistance, across which the voltage is measured.
The current measurement device includes an analog-to-digital converter which measures the current and provides the measurement in a digital format to a microprocessor which computes the state of charge of the associated battery system.
According to one aspect of the invention, a device for monitoring current flowing through an electrical circuit includes a current shunt plate connected between at least one terminal of the electrical circuit and an electrical load; a circuit board mounted to the current shunt plate at at least two connection points; and a current measuring device mounted on the circuit board, the current measuring device being adapted for measuring a voltage drop between the at least two connection points and determining the current flowing the current flowing through the electrical circuit.
A portion of the shunt plate between the at least two connection points forms a shunt resistance R which is related to geometric properties of the current shunt plate.
The shunt resistance R may be determined based on the following equation: R=