Rechargeable USB "AA" Batteries. Has anyone used them? I have a cosplay project where I'm creating a "Megaman" aka Rockman type of arm cannon (it's actually based on DC's Cyborg). Anyhoo, I've been weighing options like using 3xAA alks or 4xAA nicd (or otherwise 1.2V)--inclcuding various combinations of less or more cells with a voltage regulator; boost up or step down as appropriate.

there are 4 lighted segments (15 leds of WS2812B x 4). I also of course have to power the Arduino Nano as well. I'm flexible on led brightness so I'm just going to tune it [code it] to whatever looks adequate for my purpose. I am aware of the 50ma draw of these units at full brightness 

My original plan was to just keep it easy (read lazy) and use 3 AA alks per 2 segments, and another 3 so the nano can have it's own supply. So 9 cells in total (without any additional regulation). Before you judge me--weight, volume, and especially area are definitely big factors in my decision.

So that's a long way to get to my actual question. Has anyone used these new types of USB rechargeable batteries? They seem to have the best of both worlds with the power of an alkaline but the consistency and sustainability of a NiMH /NiCD as they have internal regulators that produce a steady 1.5v (until they don't--which I'm more than cool with)

Short of having a properly regulated 5v power supply, are these a good option if I want to be slightly more responsible than throwing in whatever other AAs I have lying around? They definitely check the box on my space/mass requirements. I'm sure they do fine with most consumer electronics, but as far as arduino and any other custom/hobby 4.5-5v applications how reliable are these? Even if you haven't used them before I'd be curious of your thoughts. I'm a novice at best when it comes to elec engineering.

Yes, they are expensive. Thanks all!

examples:
https://www.amazon.com/Rechargeable-Batteries-Quick-Charge-Integrated-Protection/dp/B07F27PK2M/ref=sr_1_5?crid=1RTQUCZYG4KBM&amp;dchild=1&amp;keywords=usb+aa+batteries+1.5v&amp;qid=1588280164&amp;sprefix=usb+aa%2Caps%2C242&amp;sr=8-5

https://www.amazon.com/Blackube-Rechargeable-Batteries-Lithium-1500mAh/dp/B07D9K2H9H/ref=sr_1_11?dchild=1&amp;keywords=usb+aa+batteries+1.5v&amp;qid=1588282813&amp;sr=8-11
Those "batteries" are actually a 3.7V¹ ~750mAh Lithium rechargeable cell with a 1.5V switching regulator and 5V charge circuit built in. 

In about the same space as one of those, if you throw away the charge circuit and switching regulator, you can get a single 18650 Lithium rechargeable cell at 3.7V¹ (nominal) and three times the capacity. Two of those plus a small 5V switching regulator² would give you more power capacity and longer run time in a smaller space than the equivalent voltage of these strange "batteries".



¹ Nominal

² Use a good one with a Li-Ion battery protection circuit and maybe a built in 2S charger too for convenience