Thanks for the review. Just so you know any ~3.7v lithium ion battery can be replaced with any lithium ion battery, all the charging protection/regulation is controlled on a small circuit board thats wrapped inside the respective batteries. You can upgrade or downgrade the mAH capacity on the batteries too, so you can replace the 2000mah with a 4000mah if you want double the capacity, it just has to fit inside. This usually requires soldering though, and make sure the red wire doesn't accidentally touch the white.
With 3M headphones I notice that if you unplug the cord to a listening device, the battery life last longer. But Ive had mine for several years until the headband broke within the cushion. Ive worn them so often that I wasnt that surprised that something would give.
@dansouza6284 yes. It's just an android app that bypasses the max volume on the phone itself. I wouldn't recommend using it in speaker mode but for headphones it's perfectly fine.
