I've been using the Next Gen RF/IR blasters (2 sets actually) in a Harmony 620 for about 8 months now without problem. I'm not sure about the 650, but the 620 uses 4 AAA's. The RX tx likes to be in one of the bottom slots, and I use NIMH rechargables for the rest. Mine gives a strong enough signal that it is easily received through my floor to the 2nd unit upstairs to control my cable box from my media room. I also use the Logitech PS3 adapter and between the Harmony, Next Gen, and PS3 adapter, I can control everything I have (Lutron IR dimmers, Denon AVR (2 zones of speakers hooked up), VS Pro8100 pj, PS3, Sony DVD, Motorola DVR, and a cd changer. The typical charge lasts right around a month with moderate use.