Note the small link near the top titled "Comparator" if you want to generate comparison graphs between different batteries.
1.5V Li-ion rechargeable AAs are 3.7V cells with DC-DC buck converters attached to reduce the voltage. The main reason to use them is poorly-designed[0] devices that don't play well with NiMH. There may be some standby power drain from the electronics, and these are less compatible with voltage-based battery status monitoring than NiMH (NiMH gives a false low reading; bucked Li-ion gives a constant false full reading).
Modern low-self-discharge NiMH has very good performance and shelf-life; the white Panasonic Eneloop is the gold standard in this category; the black ones have higher capacity, but wear out in fewer charge cycles.
[0] Even if designing for alkaline without NiMH support isn't a design flaw per se, a device that doesn't work at 1.2V leaves about half the energy stored in an alkaline unused.
Note the small link near the top titled "Comparator" if you want to generate comparison graphs between different batteries.
1.5V Li-ion rechargeable AAs are 3.7V cells with DC-DC buck converters attached to reduce the voltage. The main reason to use them is poorly-designed[0] devices that don't play well with NiMH. There may be some standby power drain from the electronics, and these are less compatible with voltage-based battery status monitoring than NiMH (NiMH gives a false low reading; bucked Li-ion gives a constant false full reading).
Modern low-self-discharge NiMH has very good performance and shelf-life; the white Panasonic Eneloop is the gold standard in this category; the black ones have higher capacity, but wear out in fewer charge cycles.
[0] Even if designing for alkaline without NiMH support isn't a design flaw per se, a device that doesn't work at 1.2V leaves about half the energy stored in an alkaline unused.