After battery is charged it slowly drains and I have tried a new battery
My car has an automatic transmission.
Depending on the van and its accessories the first thing to do is to look and see if the interior lights or hood light are staying on. Take the bulb out of the hood light and see if the draw goes away. If you do not know how to check the draw then I suggest getting a technician to check all of the systems for an excessive draw on the battery. The most common is the interior map light staying on. Also check the map light latching mechanism to see if it is broken.