All, I think electronic ear defenders are great. However, they do tend to have funky battery sizes and always tend to run out when you don't want them too.
I have a Petzl headtorch that charges off a micro USB cable. Fenix also do series of torches that are chargeable from micro USB. Why have none of the ear defender manufacturers made one?
With a micro USB you can charge it at your desk, home or car really easily and not have to worry about various proprietary chargers. Simples. Come on Impact, Peltor et al, get it on with doing it!