  Liquid metal batteries (LMBs) are discussed today as a cheap grid scale
energy storage, as required for the deployment of fluctuating renewable
energies. Built as a stable density stratification of two liquid metals
separated by a thin molten salt layer, LMBs are susceptible to short-circuit by
fluid flows. Using direct numerical simulation, we study a sloshing long wave
interface instability in cylindrical cells, which is already known from
aluminium reduction cells. After characterising the instability mechanism, we
investigate the influence of cell current, layer thickness, density, viscosity,
conductivity and magnetic background field. Finally we study the shape of the
interface and give a dimensionless parameter for the onset of sloshing as well
as for the short-circuit.
