Defects in semiconductors can exhibit multiple charge states, which can be used for charge storage applications. Here we consider such charge storage in a series of oxygen deficient phases of TiO$_2$, known as Magneli phases. These Ti$_n$O$_{2n-1}$ Magneli phases present well-defined crystalline structures, i. e., their deviation from stoichiometry is accommodated by changes in space group as opposed to point defects. We show that these phases exhibit intermediate bands with the same electronic quadruple donor transitions akin to interstitial Ti defect levels in TiO$_2$-rutile. Thus, the Magneli phases behave as if they contained a very large pseudo-defect density: $frac{1}{2}$ per formula unit Ti$_n$O$_{2n-1}$. Depending on the Fermi Energy the whole material will become charged. These crystals are natural charge storage materials with a storage capacity that rivals the best known supercapacitors.
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