Lithium packs have a shelf life that starts ticking when they are made, whether they sit in a drawer or fly every day. 2 to 3 years and they loose capacity.

Glad you didn't tear it up.

I watched a guy setting up a new EVO, tinkered too long and killed his reciever battery. Unfortunately it happened during a test hop. It was sitting on the ground at 50 percent throttle and maybe a degree or two of negative pitch holding it down on a VERY gusty day. I ran in the building and got a shovel, slid it across the skids and knelt on the handle to hold it to the ground till the motor finally leaned out and quit. He was at the field yesterday with a new loaded battery checker