The method of claim 1 further comprises adjusting usable capacity of the given battery using the determined SofH of the given battery converting the adjusted capacity of the given battery to a remaining usage time for the given battery and displaying the remaining usage time of the given battery on a display of the apparatus.ДЎ0. The method of claim 1 further comprises identifying segments of time when the battery is resting, extracting voltage measurements from the identified segments of time, and constructing the present model from the extracted voltage measurements.Д©. The method of claim 1 further comprises comparing the present model to the set of fingerprints using a regression tree.ДЁ. The method of claim 4 further comprises reducing dimensionality of the voltage measurements by apply principle component analysis.Д§. The method of claim 4 wherein the exponential function is further defined as a power function as follows v( t)= a*t b +c where t is time since start of resting.Д¦. The method of claim 1 wherein constructing the present model further comprises fitting the voltage measurements to an exponential function filtering out the voltage measurements using the exponential function and smoothing filtered voltage measurements with a moving average, thereby yielding the present model for the given battery.ДҐ. The method of claim 1 further comprises constructing the present model using regression analysis.Д¤. The method of claim 1 further comprises charging the given battery until the given battery is fully charged and measuring voltage across the given battery after the given battery is fully charged.ДЈ. A method for estimating state-of-health (SofH) of a rechargeable battery powering an apparatus, comprising: providing a set of fingerprints for a battery of a given type, where each fingerprint links a quantified SofH for the battery to a given predetermined model for the relaxing voltage of the battery and the given predetermined model describes relaxing voltage of the battery over a fixed period of time while the battery is resting by fitting voltage measurements to an exponential function measuring, by a circuit in the apparatus, voltage of a given battery of the given type over the fixed period of time while the given battery is resting, where the given battery is configured to power the apparatus constructing, by a processor in the apparatus, a present model for the given battery from the voltage measurements and determining a SofH for the given battery by comparing the present model to the set of fingerprints.Дў.

Ibackupbot battery cycles