Yeah, it SHOULD, but that is the key thing there...
Unfortunately, it is very easy to purchase (and why not?) labeling material, and print up "official" Dell part numbers- and make new labels and sell old gear or bad gear on ebay. For those of us used to being in a country like the USA, it can be a bit unfathomable or impossible to completely comprehend how bogus gear can continually get on the market. Simply put, over here, in Eastern Europe, I can even get a completely FAKE dell laptop- top to bottom. They make up everything and print their own labels. How do I know? I've been where they do it.
So even that XPS you just got, or the Sager, could be completely fake, top to bottom. And the last person who got screwed that way, sold it for parts and now you got a part from it- and the cells inside it are as old as heck- and ceased being effective 5 years ago.
So that's scenario 1.
The more normal one is simply you got a battery that is DOA because it sat on a shelf too long or was overheated in a truck or discharged for too long, etc., etc.
Unfortunately for those of us who buy off ebay, this is the risk we take.
When it comes to parts though, realize that the world is a VERY big place, and elite items like laptops draw crazy schemes for people to get rich in 3rd world countries- like driving 3000 miles in an old truck to steal some and make some prototypes using old failed gear then flying them into somewhere like NewJersey to sell on ebay. Sounds crazy? Try living in a city made of cinderblocks and open sewage for 30 years and then see hollywood for the first time.
Carefull on Ebay with used or "official DELL" parts- sometimes you can score, but sometimes even the sellers don't know they got fake stuff from china somewhere or some 3rd world country. It is a lot more prevalent than it would seem to us when we think about it. Having been to those places, I'd say, almost never buy perfectly new items that are official, and at big discounts, off ebay.
Rather get it local at a store you can go in an talk to a manager if there's a problem.
for those of us who, like MrEvil and I and the original poster, choose to get used gear- the risk is what it is. It's best to learn how to repack your own (no it's not a smoke) and simply buy 9-12 cells and crack the puppy open and then epoxy it back when you're done. You'll not only learn HOW to do it on the first time (and laugh at how easy it was) but you'll be able to continue to do it in the future, for half the cost of buying a new battery, AND you might even discover how to do something fun in the process!