A battery charger and method is disclosed for detecting when a battery has a low state of health while simultaneously charging or maintaining the battery. A battery charger includes a processor; a non-transitory memory device; a power management device to receive an input power and to output a charging current; a pair of electrical conductors to electrically couple with a battery, and a display electrically coupled to the processor. The display being configured to indicate a bad battery indicator when the battery has a low state of health and whether the battery is good to start.

A battery device includes a first battery and a second battery connected in series. An electronic device for determining a state of charge of the battery device includes a sense resistor connected in series to the second battery, and a fuel gauge. The fuel gauge is configured to determine the state of charge of the battery device based on a first terminal voltage of the first battery, a first calculation current of the first battery, a second terminal voltage of the second battery, and a measurement current of the second battery measured through the sense resistor. The fuel gauge calculates a second calculation current of the second battery using a battery parameter of an equivalent circuit model, corrects the battery parameter when a difference between the measurement current and the second calculation current is not less than a threshold value, and calculates the first calculation current using the battery parameter or a corrected battery parameter.

A battery device includes a first battery and a second battery connected in series. An electronic device for determining a state of charge of the battery device includes a sense resistor connected in series to the second battery, and a fuel gauge. The fuel gauge is configured to determine the state of charge of the battery device based on a first terminal voltage of the first battery, a first calculation current of the first battery, a second terminal voltage of the second battery, and a measurement current of the second battery measured through the sense resistor. The fuel gauge calculates a second calculation current of the second battery using a battery parameter of an equivalent circuit model, corrects the battery parameter when a difference between the measurement current and the second calculation current is not less than a threshold value, and calculates the first calculation current using the battery parameter or a corrected battery parameter.

A battery monitoring apparatus includes a circuit board, a signal control unit configured to cause a predetermined AC signal to be outputted from a storage battery through a first electrical path, a response signal input unit configured to input, through a pair of second electrical paths, a response signal of the storage battery to the AC signal, and a calculating unit configured to calculate, based on the response signal, a complex impedance of the storage battery. The first and second electrical paths are provided on a major face of the circuit board. On the circuit board, there is defined a first region which is surrounded by the first and second electrical paths and two terminals of the storage battery. The size of the first region is set to have an electromotive force, which is induced in the second electrical paths by the AC signal, be within an allowable electromotive-force range.

A battery monitoring apparatus includes a circuit board, a signal control unit configured to cause a predetermined AC signal to be outputted from a storage battery through a first electrical path, a response signal input unit configured to input, through a pair of second electrical paths, a response signal of the storage battery to the AC signal, and a calculating unit configured to calculate, based on the response signal, a complex impedance of the storage battery. The first and second electrical paths are provided on a major face of the circuit board. On the circuit board, there is defined a first region which is surrounded by the first and second electrical paths and two terminals of the storage battery. The size of the first region is set to have an electromotive force, which is induced in the second electrical paths by the AC signal, be within an allowable electromotive-force range.

An active isolation detection method may be used with an electrical system having a battery pack connected to a high-voltage bus. The bus has positive and negative bus rails, each having a respective rail-to-ground voltage. The method may include connecting variable resistance element to the high-voltage bus, and determining input information indicative electrical characteristics of the battery pack, the high-voltage bus, and/or a charging station. The method includes varying a bias resistance of the high-voltage bus, via control of the variable resistance element, e.g., via duty cycle control of a binary switch in series with a bias resistor, to produce a varied bias resistance based on the input information. A target voltage shift is achieved on the high-voltage bus as a target level of change in one of the rail-to-ground voltages. An isolation resistance of the electrical system is determined via the controller using the varied bias resistance.

An active isolation detection method may be used with an electrical system having a battery pack connected to a high-voltage bus. The bus has positive and negative bus rails, each having a respective rail-to-ground voltage. The method may include connecting variable resistance element to the high-voltage bus, and determining input information indicative electrical characteristics of the battery pack, the high-voltage bus, and/or a charging station. The method includes varying a bias resistance of the high-voltage bus, via control of the variable resistance element, e.g., via duty cycle control of a binary switch in series with a bias resistor, to produce a varied bias resistance based on the input information. A target voltage shift is achieved on the high-voltage bus as a target level of change in one of the rail-to-ground voltages. An isolation resistance of the electrical system is determined via the controller using the varied bias resistance.

A contact test device for a hi-pot test includes: a contact test device connected to a hi-pot test device in parallel by lines branched from first and second lines of the hi-pot test device by being connected to first and second terminals of a battery through first and second probes, respectively, and having third and fourth probes directly connected to the first and second terminals, wherein the contact test device includes: a first closed loop including first to third switch units, a direct current (DC) voltage source and a first continuity detection unit; a second closed loop including fourth to sixth switch units, the DC voltage source and a second continuity detection unit; and a control unit controlling turning the first to sixth switch units on and off and detecting a continuity signal of each of the first and second continuity detection units.

A contact test device for a hi-pot test includes: a contact test device connected to a hi-pot test device in parallel by lines branched from first and second lines of the hi-pot test device by being connected to first and second terminals of a battery through first and second probes, respectively, and having third and fourth probes directly connected to the first and second terminals, wherein the contact test device includes: a first closed loop including first to third switch units, a direct current (DC) voltage source and a first continuity detection unit; a second closed loop including fourth to sixth switch units, the DC voltage source and a second continuity detection unit; and a control unit controlling turning the first to sixth switch units on and off and detecting a continuity signal of each of the first and second continuity detection units.

A method for operating a battery sensor having at least one measuring resistor and at least one voltage capture device for capturing a voltage drop across the measuring resistor and for outputting at least one measured value dependent on the captured voltage drop and an evaluation circuit. The method including determining a correction value for the measured value by the evaluation circuit, and determining a first temperature value of the measuring resistor on the basis of the determined correction value by the evaluation circuit.