I registered at Tesla motors website so I could comment, but it says to login to comment, even when I'm logged in. When I click 'login' it says I'm already logg

I registered at Tesla motors website so I could comment, but it says to login to comment, even when I'm logged in. When I click 'login' it says I'm already logged in. I would like to ask if it's true or not that any batteries have become inoperable due to being drained completely. Also If that does occur, what is the cost of replacement, and is it at all covered by warranty. It doesn't seem like that answer is forthcoming...