Interesting. Thanks for the review.
Might be a good option for the Lumintop Tool’s that I gave away a few weeks ago, since they’ve got the USB charging.
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.
They’re using alkaline now.
So, these cells cannot be charged in a typical NiMH charger, correct?
Correct, they need USB power to charge.
man those discharge curves are sexy AF 
Thank you for the review. They seem a tad expensive and too many bad reviews for me at this time. https://www.amazon.com/Blackube-USB-Rechargeable-Batteries-High-Capacity/product-reviews/B07QYM4DJQ/ref=cm_cr_dp_d_hist_1?ie=UTF8&filterByStar=one_star&reviewerType=all_reviews#reviews-filter-bar
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.
Thanks for the review… but I doubt I will buy and use with this chemistry. I try to avoid any Li based rechargeable battery. I only trust Ni-Mh
Do you own a cell phone? A tablet? A laptop? A camera?
Thanks for the review HKJ !
Can these batteries be drain low before its need a recharge?
They contain protection that will disconnect the output when they are empty, they will not drain the internal LiIon cell dangerous low.
Thanks for the reply!
can we do teardown on this battery ?
I may do that later together with a few other of same type.
Is this LED only used during charging?
Can it be used to indicate remaining capacity at all?
Given the flat voltage curve, I’m guessing it’s not easy to tell how much juice is left in it.
The led is only for charging, there is no way to see how much energy is left in the cell.
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. 
Easy to get another ‘charger’. Do you lose your chargers? 
An advantage, If you want to call it that, is it only takes one USB connection to charge 1 > 4 cells. Personally I think I prefer that over the USB direct connection.
The charger is a box barely larger than a storage pack for AA. If you buy it with the charger, that’s what it gets shipped in. I guess you could store them in it. Don’t know if there is a low grade drain, but I think not.