I have a two year old of which the battery just died - the laptop will only work if plugged in. Are non-OEM batteries just as good as OEM batteries?
There's really no answer to your question. It's not about whether or not the battery is OEM, it's about the battery quality itself.
While it's impossible to check if the battery is good before you buy it (especially if online), you can definitely opt for new batteries (as opposed to used), and batteries that come with a warranty (just in case you need to return/exchange it).
You should also check the reputation of the battery maker (say, Dell), and of the seller (New Egg, for example). You can use the internet to search for reviews on products, manufacturers, and online stores. And for the USA and Canada, you can use the Better Business Bureau businesses up to find out how reputable they are.
So when looking for a new battery ask yourself:
- Is the battery new?
- Does it come with a good warranty?
- What do the reviews say?
- Can I trust this place not to steal my money, or sell me junk?
Please see this review of OEM batteries:
EDIT: Removed editorial.
I have purchased inexpensive batteries and had good luck with them so far, bought them off of Amazon. Last one I bought was for my Dell Latitude D600, seems to be working well, it was under $40 after shipping and tax. The vendor was MLC Distribution Inc.
I have seen this site recommended on many forums for quality replacement laptop batteries at reasonable prices.
I had success buying no-name batteries (after I discovered Dell wanted hundreds of dollars more for the same parts).
(if your interested, my blog post about it has more details)