US Patent 7554294 Battery health monitor

A battery health monitor (BHM) that operates as a battery-mountable full-spectrum alternating current (ac) impedance meter that facilitates monitoring a state-of-charge and a state-of-health of a battery. The BHM is used for monitoring one or more electrical parameters, e.g., impedance, of a battery. The BHM includes: a current sink coupled to the first terminal and configured to sink therefrom an oscillatory current so as to cause the battery to produce at a first terminal thereof an oscillatory voltage equal to or less than a dc operating voltage of the battery that would be present at the first terminal in the absence of the oscillatory current; and a voltage sensor configured to sense the oscillatory voltage at the first terminal.