Would charging with a moded charger(which is ment to tweak it so it charges a lot faster) have any harm on battery?
Not true buddy. check ebay they have modded cables. Those cables charge 3 hour faster. I know it . I have timed my original Cable with a 2.1 AMP charger it takes 5-6 hours. with this cable it takes only 2-3 hours.
Forexample: - Today I put it in charge at 4:30 and at 5:48 it's 58 percent from 15% .. else it would be like 29-35% .. thats the difference.
Update: - It finished charging at 6:30 .. super fast!