Pretty much everyone in this comment thread besides you seems to think that I am suggesting replacing a car's main battery with a lithium battery. I do not beli

Pretty much everyone in this comment thread besides you seems to think that I am suggesting replacing a car's main battery with a lithium battery. I do not believe I ever suggested that. While I respect that you seem to have read a more circumscribed version of my comment, I'm not sure what your quibble is. A two-pound battery pack that can be used to jump-start your car seems like a heck of a win for most people. Yes, you can start your car by disconnecting your battery and connecting a charged lead-acid battery. That seems pretty obvious. I can't think of a reason you'd need to do this, though, unless your car's main battery has gone bad. And if that's the case you will need to call a mechanic anyway. Leave alone that the lithium batteries mentioned above are advertised to supply 400 amps, enough to start many cars.