Van won't start makes a clicking sound under dashboard

Hello, this sounds like not enough power is getting to the starter. The first thing one imagines is that the battery is not strong enough to crank the engine. It may be "charged" - but is it able to handle a load? What methods have you used to test the battery and its ability to handle a load? Secondarily, check all cables from the battery -- to ground and starter -- and ensure all are complete, secure and free of corrosion.