Battery Low [Q] How can i use the kekda charger????

I have a rooted Sony Xperia Arc running unnofficial CM 11 build by mikeioannina, which stopped charging suddenly via the normal usb cable, thus I bought this kekda charger to charge the battery without using the phone. The seller told me it takes around 2-3 hrs for a full charge, but when i connect my battery to this charger, it takes almost 8-9 hrs for a full charge. Where is the problem??? Somebody pls help.... I cant keep my phone off for 8 hrs. Is it that I am connecting the wrong terminals or is it some problem with the battery????