Charging system

New me here not sure if it is the right thread to post on..anyway my firblade 929cc is baffling me with starting issues/ battery power. It's probably so easy to diagnose but it's only easy if you know how..the battery is completely dead when starting..put battery pack on it jump starting..then when out riding I stop for a while get back on battery dead again. So jump started again then same thing happens...keep the battery pack contacted to get home then the power runs out of that am stuck..when coming up to lights etc it's wanting to quit and have to keep reving it..how do I go about checking other things?? Its not the battery as its a new one ..yes probably simple to check but I Don't know how that's why am asking here..????
Matt