1990 Plymouth Voyager Battery going dead

1990 Plymouth Voyager 6 cyl Front Wheel Drive Automatic 185.00 miles

Hi in the last three months I had my starter replaced and my battery, then alternator. This past weekend my vehicle sat for four days because I decided to take the bus to work. Well this morning I went out to start it and there was loud clicking noise. The van would not turn over at all. My lights worked and the radio also worked. So I brought out a battery charger and kept in on charge for an hour. When I went to start the van it turned over and started, I removed the charger and decided to take the van for a spin. About an hour later I got back home shut the van off and it started right away. Then I waited about three hours and went to see if the van would start, no go just the clicking noise once again. Im wondering if my battery has lost the ability to hold a charge because the dashboard gauge shows the needle still in the plus side. How can I tell if the new battery I bought is faulty. For some reason the van did this during the four days I took the bus to work.