A year ago, maybe two, I was not aware that Li-ion AA-type batteries were even a thing. The closest thing I had come across, involved a Gofundme or Kickstarter-sourced idea that had 'ordinary' batteries sitting in a barely non-existent holder, with an even smaller DC-DC circuit module, that generated a constant output voltage for the duration of the battery life. Thing was, it didn't work anywhere near as well as the developer suggested, and the people that funded the venture, ended up losing hundreds of thousands as a result. But it appears to have got people thinking, and possibly was the chicken that ended up laying the egg I'm referencing here.
Instead of dealing with 'ordinary' batteries, this new battery technology starts with high energy-dense Li-ion batteries. Curious as to how they performed, I bought a handful of type AA's and a pair of PP3 type 9 volters. The 4 AA's weren't cheap, costing €30, but that included the charger as well. The PP3's were a more reasonable €6 each.
Performance-wise, both types fared well, with each subjected to the same 100mA current draw. The Liitokala brand, though fairly well regarded, claim a ludicrous 1100mAh capacity. Their actual capacity is closer to 350mAh. Instead of fibbing, Liitokala should instead have listed the battery capacity in Watt-hours (Wh), which provides a more accurate capacity measure where DC-DC supplied outputs are involved - in this instance, between 3.1 to 3.2Wh from my measurements.
The Hixon AA batteries more sensibly use Wh for claimed-capacity from the get-go. The battery manufacturer itself seems highly regarded, and my measurement results would tend to bear this out. Rated at having 3500mWh capacities, all four AA batteries measured significantly higher in my testing, coming in between 4.3 and 4.4Wh.
The main downside with this type of DC-DC battery is that you have no clue as to their remaining state of charge. A secondary unexpected annoyance is that, in use, they supply power for appreciably less time than say, NiMH batteries. This became evident over the Christmas period when I was using them to power Christmas lights. The reason is obvious when you think about it. Their constant voltage output means that they provide constant power for the duration of their charge - meaning, my x-mas lights maintain a constant brightness throughout - whereas Nimh battery voltage drops appreciably as they discharge, so lights glow less brightly, over time, but stay lit for a longer time.
In summary, it's interesting tech, but not awe-inspiring. Certain electrical appliances whose performance are effected by voltage fall-off while running, will benefit. But generally, normal rechargeables will do just fine. I won't be ordering more any time soon.
