Many people have reported using rechargeable NiMH batteries in their remotes with great success. Actually, I haven't seen any problems reported at all. I've been using a set of NiMH batteries in my 550 for almost a month now with no problems. Yesterday my wife calls me at work to tell me the remote is not working. I got home and saw that it wasn't responding to any of the buttons. The "Choose an Activity" screen was up, but nothing happened when I pushed any of the buttons. I took the batteries out and put them back and still nothing. I even tried reinstalling the firmware with no luck. Finally, I called Logitech support and was told to put it in Safe Mode and try updating the firmware again. I tried probably 10 times and could not get it to go into Safe Mode. I took the batteries out, held down the power button and plugged in the USB cable. It would boot up, briefly display "Low Batteries", and then say "USB CONNECTED". Finally, after many tries, I went to go put the batteries back in and saw that there was a sticker in the battery comparment that said something like "4 x 1.5v AAA". Just for kicks and giggles I looked at the rechargeable batteries and they said something like "AAA 1.25v NiMH". Hmm, interesting. I believe all NiMH batteries are 1.25v and that small difference doesn't usually matter (in cameras it generally doesn't, for example). I put in some standard 1.5v alkalines and, voila!, the remote came back to life! Tried the rechargeables again and it worked fine for a little while and then certain buttons stopped responding again. Put the alkalines back in and it worked. I'm going to give it a few days with the alkalines just to make sure my theory is correct, but it looks like my remote doesn't like rechargeable batteries. Not sure why it worked for a month with no problems, but there it is...
