Originally Posted by
Leisesturm
It will take years before the cells in a 4x18650 battery pack wear out. I bought some new battery packs this year for my MagicShine 808 lightheads, but the old ones still aren't dead enough to throw away, so I keep them around for household use. The lightheads have been going for as long as I can remember. USB by design, is limited to 5V x 2.5W power output. This is only sufficient to charge the smallest of 'be seen' headlights, and thus USB is mainly used to charge taillights and small ancillary devices that use the tiny internal Li-ion batteries.
USB has been capable of much higher currents for years after the introduction of faster charging smartphones. The limiting factors are your charger, your cable, and if your light is capable of accepting that current. Modern chargers with some smarts to them negotiate with the device to set a charging current.
I've been using some rechargeable flashlights with the open Anduril 2.0 user interface. If you slow down the strobe party mode as far as it goes, you'll have a nice daytime running light, and Anduril also has a night bike mode (constant light, but blips about 20% brighter once a second). This is in addition to just regular rampable flashlight modes...The ~2000 lumen turbo max (1700-1800 lumen IRL) Sofirn SC31T Pro is often on sale, charges via a built-in USB C port, has more of a spot than a floody output, plus the 18650 battery is replaceable/can be charged in a separate smart charger if desired. (not included)
I also have an itty-bitty Wurkkos ts10 for daytime running light plus emergency night use (floody), and a Wurkkos ts21 (also floody, but 3400 lumen can overcome that!)