Let me ask a question about LED lights. I have two LED lights that I use. One is a Petzl e+lite headlamp which is awesome. The other is a Gerber Tempo which I have rigged up with an elastic headband to make into a headlamp. The Tempo is a great light and really cheap ($10.00 or less) but very durable. It lasts a long time too, or at least it used to. Hence my question.

My daughter and I were camping the other day and she was using the Tempo. I was impressed at how much brighter it was than my Petzl. I wondered if it had always been like that. Then after 2 or 3 hours it dimmed and went out. The strange thing was that I had put a new battery in just before the trip. But upon reflection I realized it was a rechargeable battery (recently charged). Rechargeable AAAs have slightly less voltage than regular AAAs (1.2 vs 1.5). I wondered if the light were somehow pushing the battery harder because of the lower voltage or something.

Any idea about this? I don't know much about LEDs or batteries.