I have a phillips dvd video player with dock for ipod with video ?

Okay, this is the silliest thing but both my husband and I have looked and read the instructions twice and we cannot seem to find where the batteries go, the only battery we have found is the one for the remote, where do ther rechargeable go as my machine is not holding the charge so I am assuming the batteries are shot.
It does say that it is built in but does any one know if they can be replaced.