Energizer have had "Made in Japan" rechargeable AA's forever. I've been buying them for years. They do have "Made in China" ones as well which I avoid. The "Made in Japan" ones used to have a green top but recently (in the last or 4 years) switched to a black top. The switch to a black top...
My K65 works fine with flat top 18650s. Is your carrier different? Bought mine near the end of March.
I never use protected cells and can vouch unprotected cells work fine as well. If you don't pay attention to your cells it might benefit you to use ones with protection.
I got my Vinh modded SD4Avn and do not like it as well as the Sunwayman D40A Vinh modified (I have 4 of them). It doesn't throw as far as either of my de-domed D40A lights and the transition from spot to flood is much nicer on the D40A.
I like the larger switches on the SD40A (Lumintop) and...
That has been my experience as well with the Centura cells. Most of my Blue cells died early and none of them had much over 8000mah capacity. The newer Tenergy cells are much better. My Imedian cells all died while most of my Tenergy cells are still going strong.
I own a bunch of Fenix stock and modified lights, also about a dozen Olights all stock. The majority of my Olights have failed even though they receive a lot less use than most of my Fenix lights. Every SR series light I've owned has either had the expensive proprietary battery pack go bad or...