Asus G73 Low battery voltage?

When I run HWiNFO64 on my Asus G73JH (which is about 2 years old) I get an indicated battery wear of only 18% (It was on AC most of the time) however I only get 8.1v. The computer shuts off when I disconnect AC, causing me to guess the battery isn't providing enough juice.
I used to have my battery light on the front blink orange but now it stays solid, and it used to (a few days ago) cap at %86, and then %74, but now it stays at 0, along with the "consider replacing your battery" message.
So, is my battery just toast? I have a Newegg extended warranty on it, but I doubt that covers batteries. If I do need a new one, what's a good place to buy from?
Thanks.

 

That does indeed sound like a bad battery, and batteries are considered consumables, so are usually warrantied separately from the rest of the unit. As for where to buy, I would just say any reputable retailer (online or not) that is an authorized Asus reseller. I'd avoid places like eBay and Craigslist myself. Ultimately the choice is yours, but I would look for an official Asus branded battery. When I think about how much a laptop like yours cost, I wouldn't really want to risk its well being just to save a few bucks on a battery. I have no doubt there are some quality third party batteries out there, but there are probably even more that are of extremely poor quality. So -- and this is just my opinion, take it for whatever it is/isn't worth to you -- unless you can be sure of the quality of that third party battery, it's not worth the risk.