PD or Iota for my upgrade?

Sal, you have such a kind and gentle approach. I won't wade into the battery-vs-resistive issue too deeply because I don't know the battery related issues. Intuitively, I can't image why a DC source couldn't put the same power into a battery as it does to a resistive load, and I'm skeptical of battery measurements because it's such an uncontrolled environment with things like temperature effects and imprecise knowledge of the DOD. But to my main question: Variances according to AC power is what I'd consider a "front end" issue, and the ability to drive a resistive vs. battery load is a "back end" issue. Two different issues, where the PD could possibly be lacking in both, however, one can't even begin to characterize the back end issues unless verified good power is being supplied to the front end. Has the PD back end been shown to be weak while the front end is verified as "well" powered?