US 6,486,636 B1Granted

Rechargeable battery measurement and calibration system and method

AssigneeAnalog Devices, Inc.

InventorsDale F. Stolitzka, Steven E. Austin

Life of this patent

Estimating the term…

Loading patent…

Abstract

A rechargeable battery measurement and calibration system for use with a removable battery pack suitably used to power a mobile computer locates current measurement and battery status intelligence outside of the battery pack, thereby reducing the cost, complexity, and power consumption of the battery pack when compared with prior art systems. A system host controls the measurement and calibration of the battery system; the host requests current measurements under both zero-current and non-zero calibration current conditions, with the resulting calibration values enabling linearity errors that might otherwise be present in the current measurements to be totally and easily identified and accounted for in a fuel gauge measurement. The present system complies with the SBS-IF specification for Smart Battery systems.

Claims26

Dependent claims

A rechargeable battery measurement system, comprising:

a power source which provides a DC supply voltage,
a battery charging circuit which is switchably powered by said DC supply voltage and which, when powered, provides a charging current suitable for charging a rechargeable battery which is part of a battery pack,
a current sensing element external to said battery pack and connected to carry current provided to and drawn from said battery pack,
a current measurement circuit connected to said current sensing element and arranged to produce an output which varies with said sensed current, said current measurement circuit connected such that it is powered by current which does not pass through said current sensing element when said charging circuit is providing charging current to said battery pack, and
a system host, said measurement system arranged such that said system host is powered by said DC supply voltage when present and by said battery pack otherwise, said system host connected to receive said current measurement circuit output and programmed to calculate battery status information for presentation to a user based on said current measurements.

2 more elements

A rechargeable battery measurement and calibration system which complies with the specifications of the Smart Battery System Implementers Forum (SBS-IF), comprising:

an AC/DC converter which provides a DC supply voltage,
a battery charging circuit which is powered by said DC supply voltage and is arranged to provide a charging current suitable for charging a rechargeable battery which is part of a battery pack in response to a command signal,
a current sense resistor external to said battery pack, said current sense resistor having a resistance R1 and connected to carry current I1 provided to and drawn from said battery pack, said current I1 developing a voltage across said resistor given by the difference between the voltage V1 at one of its terminal and the voltage V2 at its other terminal,
a current measurement circuit connected across said current sense resistor and arranged to produce an output which varies with current I1, said current measurement circuit connected such that it is powered by current which does not pass through said current sense resistor when said charging circuit is providing charging current to said battery pack,
a system host, said measurement and calibration system arranged such that said system host is powered by said DC supply voltage when present and by said battery pack otherwise, said system host connected to receive said current measurement circuit output and programmed to calculate battery status information for presentation to a user based on said current measurements, and
an SMBus physical layer which interconnects said system host with said battery charging circuit, said battery pack, and said current measurement circuit.

3 more elements

Dependencies are inferred from the claim text.