I hasten to add that the Voltron Evo team is the least
likely to ever need an arc extinguisher, because of the safe design of your battery packs. But you may be able to set a useful example for other teams, and even if they don't follow it, you may be a hero for saving one of their bikes with a few bags of sand one day.
One story I was told was of a bike with two stacks of pouch cells with no barrier between the stacks, which shorted between the stacks and continued to arc, and then burn, destroying the bike. The owner ended the story by saying something like, "Who could have predicted that?". I bit my tongue.
It's possible that, after that bike was dragged away from anything else it could set fire to, sand may have been able to extinguish the arc, followed by water to control the fire.
On observing another team's bike with exposed fuses and contactors while visitors milled about it, I asked a team member, "So if I touched the wrong two points there, would I be dead." He replied jokingly, "Sure. Would you like me to show you which two points. Is that your aim in life".
He showed them to me. They were bare bolts only about 50 mm apart, with unfused 400 V coming straight from the battery. I said, "You wouldn't want to drop a spanner across there." He reached into a toolbox and pulled out a spanner with one crescent blown away.
I said, "You didn't do that across those two points. If you had, the arc wouldn't have stopped until the battery went flat and the bike would be a charred mess. He stopped smiling and put the cover back on.
Again, if such an arc had
started between those two points, it's likely that a single unopened bag of sand dropped on top of it, would have extinguished it. Of course you won't be able to see
anything for the blinding light, but after a few bag lobbing attempts, one bag might succeed.
Few people seem to appreciate the difficulty of extinguishing a DC arc from a battery, because most of their experience has been with 24 volt batteries or less, and there is a threshold for maintaining an arc, in air, that is just above that voltage.
And few seem to understand the difference between an arc and a fire.
A fire needs fuel, heat and oxygen (or other oxidising agent). An arc needs none of those. It just needs volts, amps, proximity and any kind of gas at all (which it proceeds to ionise, i.e. turn into plasma).
I hope everyone has read How Plasma Boy got his name
If he'd dumped dry sand on it instead of baking soda, it would have been a very different outcome. Baking soda is good for fires, because when heated it generates carbon dioxide which excludes oxygen.
But the arc just thinks, "Carbon dioxide, yum. That's as good as any other gas to me. Just watch me turn it to plasma."
It says the same about water, because any water that hits it turns into that gas called steam, which it happily ionises too. In fact an arc can continue while completely submerged under water. It just forms a bubble of ionised steam around the arc.
To put out an arc, carbon dioxide and dihydrogen monoxide
are no use at all, you need silicon
dioxide (silica or quartz). "There, try ionising that
ya bastard!", you say as you toss the sand at the arc. Silica doesn't turn into a gas until it gets to 2,230°C. But indeed arcs are hotter than that, and some of it will
vapourise, but more of it will melt and fill the space, excluding all gasses.
10 kg of sand (in four 2.5 kg bags) may not be enough in some cases, but the idea is that 10 kg is small enough not to be too annoying for any one team to lug around, and if someone's bike goes up, everyone comes out with their 10 kg. And in fact, you wouldn't have to lug them around at all if you could leave them at the venue for next time.
And heck at $2.50 a bag you could hand them out for free with your team logo on them.
But of course there is no substitute for proper design and insulated tools.
[Edit: Replaced "or if not, it may have extinguished the subsequent fire where water could not, because of extreme temperatures." with "followed by water to control the fire."]