I can’t help noticing that in that case inside the battery the voltage of the li-polymer battery is bucked down to 1.5V and then by the flashlight driver boosted up again to the led voltage.
One of the big problems with these batteries is the misunderstanding and ignorance of the purchasers.
They can be useful but have a fairly narrow band of optimal uses. They work, but aren’t very cost effective for most very low drain applications, nor do they work well in high drain uses. The voltage converter heats up. Not good for camera flashes/strobes.
Some devices that really seem to require the 1.5v and have modest drain do well. Some small devices work better: battery operated beard trimmer, nose hair trimmer, electric toothbrush and the like.
I now have 12 of a brand called [Tenavolt], and generally like them….so far. Long term use to be determined.
Only buy them on special at about $2.50/cell. Full price is exorbitant.
The one thing about these Tenavolts cells is that they don’t have a usb port, so you’d better not lose the supplied charger, but if you have 12 of them, then I guess you already have 3 of their chargers as well.