Product review (1 stars): Save your time and your guitars: buy something else
I purchased a bunch of these for my guitar cases.  They are crap.  Batteries do not last long and, one by one, they have all failed.
The tiny piece of metal that they bend to make contact with the bottom of the battery looses contact and... I would rather be playing music than constantly messing around with these things to get battery contact.
I did call Planet Waves, and they told me to pull the battery and jiggle the little piece of metal or bend it some.  They tried, and I have purchased many other Planet Waves products and found the other products fine.
Save your time and your guitars: buy the little Taylor unit.