1st :

Apple still offers refurbed PBs in the day and ages ???? W !!!!! T !!!!!! FRACK ????????

Just take a close look on your PSU, there are some faint scribbling on it right next to the detachable plug there should be 65W (in a box).

If it reads 45W instead your PSU was made for iBooks and won't be sufficient to run the PB and charge the battery at the same time.