Say you made this, but insulated... does a car battery have enough structural strength in the terminals, though? I imagine you're left holding a handle with two terminals and half a cell stuck to each.
Yeah, they'd be fine. It's surprisingly difficult to break them apart. The load would spread out to almost the full width of the battery on either end (ie the plates attached to the terminals against the underside of the lid).
Some of the models I ship use plastic straps that hook onto the seam between the lid and base and you can really toss em around before they take damage. (some people are less than gentle with parts :/ but I'm not the manager so 🤷)
Some of the larger batteries with screw terminals might not survive, but the ones where these clamp style are used would be fine.