I did a bit of testing of My PeetPen L21 last night, using one of my 2013 era Panasonic NCR18650b, to which I added a dollop of solder to the + to make it work as a button top, back then. This was more to test the remaining capacity of the battery than any in depth review of its capabilities.
I downloaded a Lux app for my smart phone, and stood the L21 on its endcap pointing at popcorn ceiling, on high, and when cold it was measurng 24lux with phone flat on table next to L21.
In about 10 minutes as the light got hot, this lowered to 15lux and basically stayed there until the battery was drained to sub 3 volts. The light had gone dopwn to 11 Lux in the 3v range. had taken out the battery and it was 3.03, and returned it and put it back on high, 15lux, but within minute it was flashing 3 times, and then shut off.
I recharged the panasonic cell inside the Peetpen, using my USB meter to count mAH. 2915mAH.
I am not sure how much of those mAH were turned to heat during the conversion from ~5v to 4.2v within the light, but this ncr18650 cell has took more than double the mAH of the cell provided with the PeetPenL21.
My cheapo 2 for 10$ headlamp measured 1 lux on the table next to the L21. It/they consistently requires between 600 and 700 mah to go from dim uselessness to 'Full' they draw ~250ma or so with a 4.1x volt battery and last about 2.5 hours. It will shut off somewhere below 2.91 volts. It's actually a good candidate for a better battery, and might get the ~ 1400mah peetpen L21 provided battery which claims 1800mah
The '1200mAH' 18650 battery I removed from my portable BT speaker degraded quickly when cycling it in my ancient HF led headlamp designed for 3 AAA batteries in series, dropping to 3 volts nearly instantly under the 120ma load. I decided to drain it fully by leaving the light on. 3 days later it was still glowing, and still measured 2.32v. I then gave up trying to drain it dead and will recycle it as is.
The BT speaker when new, in 2017, would last ~5.5 hours at full volume on its internal included 18650 battery, but late last year was incapable of maintaining full volume after about 2 hours at full volume, and would randomly shut off. The Micro usb charging input also failed at this time. I added an external 18650 cell holder to the side of the BT speaker, and with the Panasonic 3400mah cell, after ~ 8 hours at full volume and it still reads 3.89v.
I could replace this speaker for under 20$, but.....I could fix it for the cost of some solder heatshrink and a 43 cent 18650 holder.
I am happy my 2013 era Panasonic NCR18650B cells still have so much of their capacity remaining, and have significantly more capacity than the cells provided with modern devices. I know they are not high drain cells, and could not power my Olight H2r on high for very long, certainly not turbo, and I would not even venture to try turbo on my Armytek Wizard c2 pro max with the 18650 adapter.
I saw on BLF, this:
Buy Rantizon Headlamp- Headlight LED Rechargeable with 2L2 LED Lights 6 Modes, 4000 Lumen Super Bright LED Head Lamp, Hands-Free Flashlight headlamp for Running, Camping, Fishing, Cycling, Hiking, Black: Headlamps - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
and for 9$, could not resist. Should arrive tomorrow.
