Except the energy is stored in the magnetic field. Superconductivity or not, you don't carry tesla-scale electromagnets around without becoming a target for hig

Except the energy is stored in the magnetic field. Superconductivity or not, you don't carry tesla-scale electromagnets around without becoming a target for high-velocity metallic projectiles and wreaking havoc with every electronic device in the neighborhood. Storage facilities for regulating grid power fluctuations are probably a much more realistic use case.