Charger is 500ma. http://www.upgi.com/media/2481/chargers.pdf
7ah battery / 0.5a charge = 14
So, 14 hours would be the best case for a full charge of a fully discharged battery. But, that’s a perfect world scenario that never happens. Battery heating, chemistry, ambient temperature, blah blah blah. Too many variables. 24-28 hours is probably a safe bet for all cases. Suffice it to say that if anybody gives you an absolute number with the data that’s been posted, it’s just a guess.
Worth a mention is that is a really basic, bare bones charger with no voltage control. A better unit will charge faster and extend battery life As a better charger will reduce the charge rate and thus the heat generated in the battery when charging is complete. A dumb charger just keeps dumping current, making heat which is the mortal enemy of any battery.