HV MAXX / won't move as used to

[neweuser]

I have an HV Maxx, two weeks old if that. It started out great, but now just coggs and stutters. You guys are the pros! So help me out if you can. When I try to hit the full throttle on it now, it just boggs. When my batts are half gone, it still does it a little but eventually i can get it to go full throttle. By then, i hardly have juice left....what's going on with this??? Someone, anyone, please HELP ME!!!!