I went on euro car parts website to look for a new battery, as my one was dying too quickly after charging it. I noticed the one I bought from them 2 and bit and years ago came with a 3 year warranty, as I hadn't kept the receipt and don't have account with euro parts I still thought I'd have to spend some money.
I went in with old battery and asked about the warranty and they'd said they'd normally wouldn't swap it without a receipt but they'd let me off this time and gave me a new one for for free and didn't even bother testing the old one.