Electronics, Lighting, & Gadgets - fenix L2D, trouble in paradise

hi fenix community,
i've been using a helmet mounted L2D (changed the battery case of my initial P2D as i needed the extra runtime) but i'm facing a sudden loss of the turbo beam 30 mins into the ride, to come back somehow dimmed, little later, 15 mins or so! What a mess after that, the beam goes from med to low brightness till i get home... the temperature is around 40F, the unit isn't any hotter than my helmet and 15 mins after my return from the ride (it's off then) it goes back on to full output! So i guess batteries and overheating are not to blame, then what? Any similarities to your Fenix? Is this a stabilization or cooling function i should know of?
thanks

no idea - try fresh batteries maybe, & send a note to Fenix

What batteries are you using? And have you experimented with different ones? It made a big difference for my P3d.

i've been using cheap no name chinese CR123 for my P2D and i originally thought that was the problem so i changed the battery body to L2D. My first two rides with AA batteries and i noticed the issues i've posted. Yesterday with fresh AA's i left the light on in room temp, in turbo mode to see how it goes. It maintained a constant turbo beam for 45-50 mins- the light was very hot already- and in less than 30sec it dimmed to 1/3 of its power and stayed so for another 20mins, gradually cooling off a bit. I turned it off then and 10mins later it was cool again and back to turbo beam for 20mins and then that was it-dimmed to death. OK, I can understand if this is an overheating protection function and i can live with that (things will be better in cold air of course), but the total turbo mode runtime -dimmed intervals not included- is nowhere near the anticipated. So far i've had 30 mins turbo time with P2D premium and 40 mins with L2D into the ride...

These are exceptionally low times compared to normal. If you are confident the batteries you are using are okay, then I would contact Fenix for a replacement. The only other thing that I could suggest would be to use the batteries in another device and determine if you get expected performance there. At 40 degrees Fahrenheit you would be the first person I have heard having overheating problems on turbo and most people have run the flashlights on turbo at much higher temperatures. Good luck.