Batteries dont seem to be charging?

I recently bought a new VP130 charger for the versapak system and the first day charged fine the transformer was warm whilst charging (which I assume it what was meant too happen) I left the batteries to charge for 6hours for the first charge, they worked fine the next day, the batteries dont seem to charge up when in the charger (theres no warmth coming from the transformer now?) I have left them for 3hours-no charge in them. Then I tried 6hours-still no charge in them, I even tried leaving them overnight but nothing?
Can someone please help me.