hmmm I thought that it was the batteries, but I used it all day yesterday and most of today (so far) with a CE2-v5 (fat wick) and it's still chugging along. Seems that around 4.7 volts (4 hours @ my vape pattern) with a dual coil, the light dims and no joy. But pop in a CE2, the light is bright and it vapes (so far) over a day. The same kinda happens in my 5v regulated MV boxmods; fresh dual coil lasts about 3 or so hours then LED blinks once and no joy; and won't fire with that carto ever again. But pop a old/new CE2 and either PV work just fine. weird.
Another thing, atty connector is mounted right on the metal lid. One probe on the center post and one on the lid reads 3.6v. Hmmm. Next time I build one, I'll make sure to isolate the connector with some silicone. Again, as it is, it works great with non dual coils just fine despite the "power leak". Could there be something odd happening inside these dual coils?