Lengthy, but thorough. I am impressed at the care taken to limit variables so as to come to a reasonably justifiable conclusion.
However..... as the presenter points out, the test was prompted by the need to purchase more rechargeable batteries because his "had disappeared", likely re-allocated to other devices by actors unknown, and equally as likely to not be returned when depleted. So much for amortizing purchase cost over 1,200 cycles.
The intro also mentioned the desire to avoid a USB charge system, so a non-USB charge system, operating at the same battery charge voltage as a USB (the lithium battery has the step-down from 3.7 to 1.5 built into each cell), was also purchased. ?!?!
Those lithium, nickel (and lead acid) batteries contain heavy metals that are environmental risks requiring recycling. Will his 'lost' batteries end up in a recycling facility, or will his unknown battery thief simply toss them into the trash bin?
For those of us on this camper forum the battery for our camping purposes has to sit for weeks or months at a time, then is expected to perform perfectly. There's no mention of the standby self-discharge rate on either of the reviewed rechargeable batteries. A fresh re-charge before packing the camper for storage may still result in a depleted rechargeable battery when the camper is reopened weeks later.
Lastly, I've been recharging alkaline AA (and AAA) batteries, the ones that accept re-charge, and not all do, reducing my battery purchase cost.
I use a common Ni-Cd / Ni-Mh selectable charger, no special charger needed.
I don't know if I'll ever reach 1,200 recharge cycles, I doubt the presenter will ever reach that either, but when these alkaline batteries of mine fail to provide the run time I expect I can toss them.
"Power" depends on the combination of voltage and current. The Ni-Mh, or Ni-Cd cell chemistry results in a 1.2 volt differential between the positive and negative sides, 80% of the alkaline's 1.5 volt difference. Using 20% more amperage from the rechargeable could compensate for the lower voltage, that is if the rechargeable cell could actually put out more amperage.
So, yeah, the device works with 1.2 volt cells. Low power consuming items like digital clocks and desk calculators have no problem with the upper power limitation due to the lower cell voltage of conventional rechargeables. Your motorized drum-banging fuzzy bunny toy? That won't beat as fast, nor as loudly, nor for as long.
Nimh batteries are now often higher capacity than their alkaline equivalents.
There are also different types of nimh- the low self discharge type (i.e. a year before 80 percent charge) vs high performance (3 months before 80 percent). Self discharge rates vary from mfg as well. Look at your lead acid batteries.. ..
I use a lot of rechargeables.. in some applications it's worthwhile (radios, daily use flashlights, kids nightlights, and a lot of other things that you don't want a battery leak in). In other applications I'll use an alkaline as the time between changes is long-sometimes a year or two. Something's are voltage sensitive.. but most are tolerant. Very few aa powered devices are current dependent.