Here is a video review of new batteries that are AA/AAA sized, Li-Ion based, and actually 1.5V.
I had messed around with running flashlights off 18650s and also there is a AA sized Li-Ion too (14450 or something) but the voltage diff was difficult. These new ones are actually 1.5V, explained at 4:25 in the video. There must be some internal circuitry for that. It also maintains a steady 1.5V for longer, but then falls off a cliff with little warning. That might be an advantage/disadvantage depending on what you are doing.
I will probably order some to try (currently using Eneloop, they are ok but their voltage is a little low too).
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