From The Hacksmith:

We made this awesome electromagnet arm bracer for the Replica Captain America shield, just in time for Captain America: Civil War. It uses a set of lithium-polymer batteries from Hobby King running in series at 72V. This produces 720kg of magnetic force at each electromagnet. That’s over 3000lbs of magnetic lifting force together!

The electromagnets are available on Amazon, and are rated for 12V, which produces ~120kg (1200N) of lifting force. We’re running them at a much higher voltage for short periods of time to create awesome power. They will overheat if you use them for over a minute at this power level!

[the Hacksmith | Via Kotaku]