I am assuming that by saying it charges from a battery charger that would be totally sparate from the van?
If you have a multimeter, or access to one, after making sure the van selector switches are in the correct positions for hook up use, and that the battery charger is ON, check the voltage at the battery terminals, it should be 13.8v or thereabouts.
If it is not, then the charger in the van has failed.
To get you through the holiday, buy a multi stage charger from a local equivalent to Argos and connect direct to the battery terminals using, if necessary, an extension cable from one of the mains outlets in the van