Good idea. I have been wondering why these tank makers haven't come up with such a simple warning lamp for low battery. Guys out there with electronic know-how can easilly fabricate these, but it would be nice if the tanks came with such indicators. All that would be needed would be a small lamp to illuminate when voltage gets to a critical low point. The way some of these tanks eat up batteries, especially with El-Mod, it would be a nice addition.