Originally Posted by
GhostRider62
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I find that 0.5 amps driving a modern LED is perfect for most riding but downhill, I want to be able to drive it with about 1 amp. On an overnight brevet, I would probably need three Cygolites. With one 21700 battery in the B01, I would make it thru the night and with one cell as a spare, I would be covered in case I needed to burn the lights during the day or if I needed the higher power at night, say if it rained.
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At 1 amp, if that is from a Li Ion battery, that is roughly 3.8 watts. If that 1 amp is measured on a USB cable, that is 5 watts. I assume you mean at Li Ion battery voltage at roughly 3.8 watts.
If you wanted the half amp for 8 hours and one amp for 2 for one night, that would be 6 amp hours, or roughly 22 watt hours.
For bike touring I carry a powerbank that is rated at 44 watt hours of power. It weighs 300 grams, or about two thirds of a pound. If you could extract every bit of power out of that (I suspect a big if) it would last two nights. Batteries alone would weigh less because they lack the case and circuitry of a power bank. But you still are looking for a lot of power and a means to store and carry that power if you stick with batteries.