An electromagnet, superconducting or otherwise, has large internal forces. If the support structure lets go, it will move. And, if part of the circuit becomes non-conducting, an inductive kickback will occur, generating enough voltage to (initially) sustain the original current.
You could cut a Li-ion battery in half, and the two halves will continue to store their chemical energy, at least until they burn up. If you cut an inductor in half (which is what this type of energy storage device is), that energy will dissipate very quickly whether you like it or not.
When working with large battery arrays I use tools that are taped in all the way except for the business end, just in case. All you need to do is drop a wrench in the wrong spot and it's party time.
Agreed about taped tools, I figured that one out right after replacing the fuse :)
A BMS typically has a small shunt that helps to figure out the state of charge as well as a large transistor in series with the current to allow switching the battery in and out of circuit.
Indeed they do.
> Not a whole lot, but enough that whether you short out with copper wire or superconductor, the effect would be the same.
Not necessarily, assuming a charged battery in many cases with a copper wire the wire will simply heat up to the point of evaporation and then break the circuit as it sprays molten copper bits all over the place. Some heat will be generated in the battery as well. Watch people mess up with starter cables for some ideas on how this tends to go (and do so from a distance...).
Using a massive copper connector that you some how instantly put across the terminal and manage to keep there would indeed make the balance of the resistance shift to the guts of the battery, which would heat up faster than that that energy can be shed and hence in all likelihood (violently) explode. Besides bits of molten lead and zinc for a car battery you now also have the joy of having to deal with spraying acid. Which depending on the state of charge of the battery can be really nasty stuff.
With a superconductor there would be no chance of the conductor evaporating first, there isn't any work done in the superconductor so it will stay cold, an explosion of the battery would be all but guaranteed.
An idle superconducting energy storage at full “charge” is not carrying a charge at all — it’s carrying a current. If you cut the wire (or blow a fuse), V = L dI/dt will generate an arbitrarily high voltage to keep that current flowing.
I imagine one would need some spark gaps and/or capacitors to limit the voltage.
https://www.lorentz.leidenuniv.nl/history/cold/DelftKes_HKO_...
The LHC had a quench event in 2008, which explosively vapourised about 6 tonnes of helium, resulting in considerable damage, and it took more than a year for the accelerator to come back online.
Probably along with a large electromagnetic pulse...
Fortunately the energy density[0] is comparable with rubber bands[1] and supercapacitors[1], so while the EMP is large, it's not terrifyingly large.
[0] at least according to wikipedia, 4-40 kJ/kg: https://en.wikipedia.org/wiki/Superconducting_magnetic_energ...
[1] 1.6-6.6 kJ/kg and 10-30 kJ/kg respectively: https://en.wikipedia.org/wiki/Energy_density
Edit: they were clear that the limiting factor on energy and power density was the forces exerted on the coils.
For now, this is restricted to special applications due to great size and cost. The great size and cost are caused mainly by the cooling systems.
(Inductors are very frequently used for very short-term energy storage (~fractions of a millisecond). For example, all energy output by a flyback converter was briefly stored in the transformer’s magnetic field. Unlike a regular transformer/forward converter, where the magnetic field is just a side effect of coupled inductors, so none of the energy is stored in it.)
And that's before we get into the purely mechanical stresses created by such an event, which likely will destroy the vicinity of the carrier of the current.
Just look at what happens if you leave something made out of metal lying around near an MRI machine when it is switched on and that's not for want of attempts to shield it.
Unlike the effect on nuclear fusion, the idea of using SC as storage devices is pretty much pure theory.
Of course it is, any kind of use of this stuff is still theoretical. That's a content free statement. But GP was making the assumption that if it works it can be used for storage. But that doesn't really follow from the properties of the material as described so far. You'd need a lot more current carrying capacity for that to become a realistic possibility.
[1] LHC Magnet Quench Protection System https://cds.cern.ch/record/259538/files/P00021565.pdf
Additionally it has no internal resistance, so you can charge such battery virtually immediately, but you can also discharge it immediately. This will be important for energy based weapons.