“Federal law requires car companies replace current batteries if they fail within 10 years.”
Do you have a reference to that ‘law’, as I’ve heard there are loopholes within it.
All EV sellers here abide by that law. However, the "loopholes" you mention speak of remaining capacity, usually the batteries must retain 70 percent capacity after ten years or can be replaced under warranty. But if they fail, then they get replaced. What is nice, is that if they fall under 70 percent capacity then they can also get replaced. Early EVs were problematic, losing much of their capacity to retain a charge after a few years, which is why the law came into being.