You have Celestial Gravitation which could explain this but it feels like an ad hoc explanation.
How it "feels" has very little to do with whether it would meaningfully affect the operation of gravity batteries. You acknowledge this much yourself, and you do not need to air your feelings in every thread that ever mentions UA.
Our friend is hopelessly confused (see above), and your bickering isn't helping. Be a good guy for a change.
No, I’m talking about gravity. The force between the earth and objects near it’s surface.
Yeah, that's gravity all right - something that's present in both RET and FET. It would be oh-so-helpful if you could stop these endless diversions.
The difference between flat earth gravity and round earth gravity, of course, is that flat earth gravity isn’t dependent on the mass of an object or its distance from the earth.
Incorrect on both counts. Imagine how much easier this would be if you had any idea what you're talking about.
The operative phrase in the definition of the equivalence principle is “locally indistinguishable”.
Indeed. An observer that is both in outer space and not affected by UA would hypothetically be able to observe a difference. Once you've identified such an observer, let me know.
In a large enough area the effects are distinguishable
A "large enough area"? What on Earth are you talking about? The Equivalence Principle says nothing about areas.
which is why I don’t believe it applies here or would explain where the energy stored in a gravity battery comes from.
Again - what are you talking about? The energy stored in a gravity battery comes from the force a body is subject to when released from a height.
Here’s why. <wasting everyone's time with an oversimplified explanation of RET>
I will say this one last time - learn the basics of the subject you're arguing against
prior to arguing against it. If you cannot do that, do not post in the upper fora.
Acceleration is a vector, It has direction and magnitude.
It is also relative. Change the frame of reference, and the direction changes accordingly. The two are indistinguishable for you and I. If you dispute this, you immediately invalidate all of RET.