Good point, the Energizer Lithiums are pretty good. Looking at a paper on them (
https://data.energizer.com/PDFs/lithiuml91l92_appman.pdf) shows that they are very resistant to temperature changes and can handle high loads without harming total capacity. It says they are just over 3000mAh per AA cell.
I'd need a massive array to replace a 2S6P 3400mAh/cell 18650 array, but I wonder if it would work out better. I'd also be able to use a lower total capacity if their self-discharge is much lower, due to chemistry and lack of a BMS... interesting.
I'd probably still want about 8-9V nominal w/6V or so dropout, so 6 AA cells to get 9V nominal, but that's 9V at 3000mAh, so to get, say, 12000mAh, I'd need 4 parallel banks, or 24 batteries total... but I may be able to get away with 3 banks/18 batteries. $1.25 or so per battery makes a full year run about $25-30. Not bad.
Now I wish I had asked first or thought of this myself without spending money on the 18650s. Guess I'll have to find some other use for them. Thank you.