Was that 7.76 volts that you measured? If so that battery was beyond dead. You certainly can bring lead acid batteries back to life especially if the internal structures are still fine, but I have never seen one at 7 volts. In my experience even you bring it back it may not have the same capacity as before. Depending on how much time or passion you have, it's less trouble to replace it.
I also suggest checking the acid levels. Open up those six top screws and add distilled water if it's low. Don't add anything else. No salt, no sulphuric acid. Just distilled water.
Best of luck.