# Can a 'superconductor battery' , theoretically at least, last forever? Even if it is being used? [closed]

One of the amazing 'killer apps' of a cheap, non-toxic, high-temperature superconductor is storing electrical energy in a large current that loops around indefinitely.

If this could be scaled down, it could result in a 'superconductor battery' for your laptop, or whatever.

But, does actually USING the electricity in your smartphone or whatever 'use up' the electricity?

Or would it never need to be recharged?

• A flywheel that has no friction still slows down whenever you extract energy from it. It only spins forever if you leave the energy in it, in it. Zero losses doesn't mean energy producing. – DKNguyen Feb 16 at 16:21
• "Conservation of Energy".... one of the fundamental physical laws. You can't extract energy from a system w/o that system losing energy. – Kyle B Feb 16 at 17:00
• Hmm, wouldn't high-current superconductor loops also produce a strong magnetic fields? That's how MRI scanners tend to create theirs. I wonder if that's very practical for a laptop battery... – marcelm Feb 16 at 17:15
• @marcelm Anything with too strong a strong external magnetic field is not permitted on most aircraft. We had to make modifications because the field caused by some fancy gadgetry which shall go unnamed was capable of disturbing the (backup) magnetic compass by more than 2°. – Spehro Pefhany Feb 16 at 17:45
• I’m voting to close this question because it's another of those free energy questions without any research. – Andy aka Feb 16 at 17:49

The energy in an inductance L is E = $$\0.5I^2L\$$. To store much energy that way relative to a battery you would need a lot of inductance and/or a lot of current. All superconductors have limits in current density and limits in magnetic field (and lower limits in combination) so you can only go so far depending on the material, temperature (colder is better) and whatever enormous pressures you can subject it to (more pressure is better).