Duracell AA's getting warm

Hello I have a Fenix LD 20 that we like a lot. Haven't used it much sine buying. I had batteries in it that worked really well. (Think they were Sears brand Die Hard).

The other day I had to replace them and put in Duracell "copper top" AA. Exp. date Mar. 2016.. Then when using the light on "high" one morning, noticed the light body feeling warm. Now when we switch it on it seems to go to "med" bright.
So, is this normal? I think not. Any recommendations for AA's? And, honestly, I have lost respect for battery makers over the past few years. Quality has gone down. Leakage etc.... Thanks!

Warmth when running your light in higher modes is normal, and in fact a good thing - the LED uses the whole flashlight as a heat sink, so some warmth means everything is contacting nicely and heat is flowing away from the emitter. With higher outputs, room temp would be a bad thing, as would too hot to hold; warm is just right.

Rechargeable Eneloop batteries will save you a lot of money in the long run, and give you much better output over time than alkalines can (up to 3 or 4 times the runtime in some instances,) without the threat of leaking or swelling.

^^^ Everything he said.

Get yourself one of the Panasonic Eneloop bundles that includes 4 regular (white) Eneloop AA batteries and a charger. Not all chargers are equal, though. You want the Panasonic BQ-CC17 or the Panasonic BQ-CC16.

Both got good reviews from CPF Member HKJ.