This chapter describes the application of solid-state NMR spectroscopy for investigating battery electrode materials at controlled state of charge. Magic-angle spinning NMR gives the highest possible chemical resolution, but only allows these often metastable electrode materials to be studied in an ex situ manner, i.e., outside the electrochemical cell, with a risk of oxidation and chemical relaxation. Complementary to the MAS NMR approach, we therefore explain the use of dedicated static NMR probes optimally designed for coupling to battery cyclers. This in situ approach allows electrode materials to be studied inside electrochemical cells during repeated charge and discharge cycles. As electrode materials are generally paramagnetic or conductive in, at least, certain charge states, one of the NMR challenges is to deal with the large line broadening and shifts. In conjunction with density functional theory computation described in this chapter, however, these paramagnetic and Knight shifts are, in fact, rich sources of detailed information about the underlying materials’ structure.