96 Ford Explorer battery drains while not in use. Car is used infrequently. If not driven for more than 1 week, the battery is drained and the car won't start. Alternator was replaced about a year ago. Battery was replaced a few months ago.

Hi. The problem is something on the car is draining the battery, but finding what is draining the battery is not easy.The first thing that comes to mind is if there is a light in the trunk is it going out when the door is closed?This is a simple thing but enough to drain the battery in a week.
One of the main parts of the electrical system is the alternator which has the main battery + cable attaches to it and therefore leakage (drain ) can occur when a part of the alternator goes faulty (usually the regulator ) I have replaced quite a lot for this problem.
The way an auto electrician would find the problem would be to put an amp meter on a battery cable and isolate one system at a time until nil or nearly nil amps are recorded.
Ihope i have been of some help to you, the problem is not an easy one to solve (like looking for a needle in a hay stack).
John( South Wales UK )

I always start at the fuse box to see what is drawing power and look to see what it is because you might have a short or some thing is drawing to much power that's not ment to