Abstract: A method of maintaining a rechargeable battery pack having a plurality of rechargeable batteries. The method includes measuring charge-level for the rechargeable batteries; and selecting a first battery set including a doner battery having a high charge-level, and a recipient battery having a low charge-level that is less than the high charge-level of the doner battery. The method also includes: rebalancing the first battery set; measuring a rest profile of the recipient battery after rebalancing the first battery set; and determining battery health of the recipient battery based on at least the rest profile.

Abstract: A system and method for measuring thicknesses of layers of a multi-layered structure, The method includes generating a terahertz wave pulse, transmitting the terahertz wave pulse to a multi-layered structure having multiple layers of materials, receiving reflected terahertz wave pulses reflected by boundaries between the multiple layers as the terahertz wave pulse penetrates the structure, and processing the reflected terahertz wave pulses to: (i) measure the time delays associated with each of the reflected terahertz pulses and (ii) determine a thickness of each of the multiple layers of materials based upon the time delay and a material refractive index of each of the materials.