Those use a lithium ion cell, so they have a buck converter to step the voltage down to 1.5V, which will always use some power. They are not suitable low draw devices because of the high self discharge rate. They can’t be used in high draw devices because the buck converter can only supply a limited amount of current. They also produce noisy power which can cause issues with radios and audio equipment. The USB port and charge circuitry take up a lot of space, so you get less capacity too. A low self discharge NiMH cell will be better for almost any use.
This appears to be a 14500 lithium ion cell (same physical size as AA), putting out 3.7v for a device like this flashlight that supports it. No voltage step down, just charging circuitry on-board.
Those use a lithium ion cell, so they have a buck converter to step the voltage down to 1.5V, which will always use some power. They are not suitable low draw devices because of the high self discharge rate. They can’t be used in high draw devices because the buck converter can only supply a limited amount of current. They also produce noisy power which can cause issues with radios and audio equipment. The USB port and charge circuitry take up a lot of space, so you get less capacity too. A low self discharge NiMH cell will be better for almost any use.
This appears to be a 14500 lithium ion cell (same physical size as AA), putting out 3.7v for a device like this flashlight that supports it. No voltage step down, just charging circuitry on-board.