Cordless drill Batteries that discharge when sitting awhile.

[SideShow Bob]

It never fails, I go to use my cordless drill (DeWalt 18V XRP) and both batteries have discharged. Before I put it away the last time, less than a month ago, I charged both of them up and put the little plastic caps over the contact area and stored evevrthing in the carry case.
Now, I go to use the drill and one battery is discharged to the point of no power and the other one seemed to have a charge, but died about 1/3 into the first hole that I drilled. GRRRRRR !
These are fairly new batteries, I replaced the old ones that were getting very weak and spent more time charging than working.

What drills do all of you have that don?t discharge the batteries from just sitting for a little time ? Is there such a thing ?
As soon as I can afford a new cordless that will stay charged, I will replace this DeWalt.