The argument is, what warranty if void? The battery only (as you assume), or the entire car? The act referenced, is all about this difference. Lets argue on the same page.
The standard approach here is warranty doesn't cover the part you damaged through misuse. So if you stab the car seats with a big knife, they won't give you new seats, but that doesn't void whole warranty.
Some things do void entire car warranty, those are pretty standard as well. Things like salvage title, submerged in a flood etc.
Others void out powertrain warranty or larger areas, usually pretty logical (flash cars computer with a tune, race car and destroy engine probably one of the more common ones?) Even though just engine may be obviously destroyed, you might lose warranty for entire powertrain (clutch / transmission etc).