Problems with removing propane / battery when storing

Out of sight, out of mind... one advantage for a cover is that it is another barrier a thief has to deal with (even though it can be dealt with with just a few knife slashes.)

One solution would be to buy or have built a locking aluminum enclosure for the batteries. A good one will resist a prybar. As for the propane tanks, there isn't much one can do other than remove them because they are in high demand (the tweakers love them for anhydrous ammonia storage.)