So I've had a Lumina 650 for a little over a year now. Use it for commuting a couple of times per week (in the late fall and winter both directions). Keep it charged up. Never had a problem . . . until last night.
On this light, you press the power button once for low, another press switches to medium, and a third press switches it to high. Hold down the button and it shuts off. Hold it down longer and it goes into seizure mode. As I said everything worked as it should until last night. As I was getting ready to leave my bike locker, I switched it on, but no matter how many times I pressed the power button it wouldn't switch to medium or high. Fortunately I don't usually need more than low (even on the unlit MUP), especially with my helmet lamp at the ready.
When I got home I put the unit on the charger the power button remained blue (indicating charging is complete), instead of illuminating red. I unplugged it and turned it on, and IIRC I got it to cycle up to medium power for a few seconds before it automatically switched back to low power (the Lumina 650 automatically switches from high to medium, and apparently from medium to low, when battery voltage drops below a certain threshold). I plugged it back in and the power button lit up red, but soon (much too soon, since I had used it for the entire commute) turned back to blue.
My guess is that the battery is no longer capable of taking a full charge, and shutting off before it's completely charged. So my questions are 1) has this happened to anyone else, and 2) is there anything I can do about this (NR does not use user-replaceable batteries)? I'll be contacting NR tomorrow to see what they suggest, but thought I'd ask here first.