My iPhone won't charge?

[sxg l]

My iPhone will charge when connected via USB to computer, however it will only charge roughly 3/4th of all the way using this method. Then when I use the outlet USB adapter it was working fine then the little adapter broke. (I know the adapter broke because we use it to charge a blackberry phone too and it wouldn't charge with phone however the cord still charged my phone from a computer [3/4ths the way].) so I went on eBay and got a generic adapter that looks 100% like the authentic one, makes me wonder if it really is generic. Anyways when I plug it into that it worked fine the first day I got it but now today when I plug it in it shows it as charging but it drains my battery all the way out instead of charging it! The computer method still works but doessnt charge all the way which is frustrating. Please help