Recording at a low (but still intelligible) bitrate and uploading it when connected to power would be pretty easy on the battery.
https://ryanplant.net/love.wav
Its only mistake was missing the "you" in "you want to be."
Codec2 remains fairly clear down to human ears down to 2.4 Kbit/sec but I had no luck getting it recognised, even with much simpler and clearer samples.
This individual anecdote tells you nothing about the state of the art, but I wanted to note it anyway because I was astonished at how well 6 Kbit/sec is handled.
But the love.wav gives a bit rate of 768kbps, 6 sec of audio at 571 KB storage size.
Another poster also did the math on 5.6 kbit/s (700 bytes/s).
> 5.6 * 60 * 60 / 1024 / 8 = 2.4609375 MB/hr
But should that 5.6 not be 768 to get love.wav voice quality? What am I missing like a moron?
Thanks for the example and anecdote, something to actually grasp in trying to understand the problem.