Anything that uses a pad lock will be easy picking for thieves including your B&D battery case metal strap.. They come equipped with bolt cutters and dremal type cutting tools.
Metal boxes with lever type key locks is a good deterrent against thieves. You also have to keep in mind that once you have been hit in your neighborhood then it may happen again and again...
The best you can do is slow them down with anything and hopefully they go after your neighbors easy picking items...
My trailer also has motion detector lights but I guess that probably only gives them good lights to work with... Having alarms going off in the middle of the night at campgrounds will have other problems for you to deal with... A motion detector that turns on an old fashion fence shocker setup might go along way. Just be sure your pocket remote is always working.
Roy Ken