Abstract: This invention relates to testing to determine the residual recoverable energy of a battery of cells or a single cell, without requiring any electrical connection to the battery or the addition of special materials, substances, or devices to the intrinsic cell, and therefore, the remaining useful life of the battery or single cell. Two different embodiments, both of which rely on the fact that the electrodes of a battery or cell undergo chemical change during discharge, are disclosed. In the first embodiment, gamma radiation is transmitted through an electrode of the battery or cell and the level of the radiation exiting from the electrode is measured. This measurement is correlated with a known value obtained for that battery or cell before discharge has taken place. The second embodiment utilizes a beta or photon backscattering technique. A battery or cell undergoing test is subjected to beta or photon radiation and the backscatter is measured.