CMV: Lithium-ion flashlights have made AA lights largely obsolete for prepping

I’ve been testing and comparing different flashlight platforms recently, and the more I look at the numbers, the more it seems that modern lithium-ion flashlights (18650 / 21700) have basically made AA-powered lights obsolete, even for preparedness scenarios. The biggest factor is energy density and runtime. A typical 21700 lithium-ion cell stores around 15–18 Wh of energy (about 4000–5000 mAh at ~3.6–3.7V). In comparison, a good AA NiMH battery stores roughly 2–2.5 Wh. So in practical terms: - 1× 21700 ≈ the energy of about 6–7 AA batteries - In real flashlight use, this usually translates to 4–5× longer runtime than a single AA That means fewer battery swaps and much longer usable runtime from a single cell. Brightness is another major limitation of AA lights. AA batteries simply cannot deliver high current without major voltage sag. Because of this, most AA flashlights struggle to exceed 300–400 lumens, and even when they do it’s usually a short turbo burst before stepping down. Lithium-ion cells like 18650 and 21700, on the other hand, can easily supply the current required for modern LEDs. That’s why many modern lights produce 1000–3000+ lumens and sustain far higher brightness levels. But the advantage isn’t just peak output — low-mode efficiency is where Li-ion lights really shine for prepping. For example, I recently tested a Convoy flashlight using a lithium-ion cell and measured over 200 hours of continuous runtime on the lowest mode. That level of output was still easily enough to light up a medium tent and perform basic close-range tasks like organizing gear, reading, or cooking. That kind of runtime from a single cell is extremely practical for preparedness. Instead of constantly swapping AA batteries, you can run a light for days or even weeks on a single charge depending on usage. Modern lithium-ion lights also bring several other advantages: - Much higher maximum brightness - Higher energy density - Fewer battery changes - Rechargeability (often with built-in USB-C charging) AA lights historically made sense because: 1. AA batteries were universally available 2. Lithium-ion cells were less common 3. Chargers were inconvenient But today: - 18650 and 21700 cells are widely available - Many lights include built-in USB charging - They can be recharged with power banks, vehicles, or small solar panels So for preparedness, it seems more practical to rely on high-capacity rechargeable cells rather than stockpiling disposable AA batteries. My current view is: «Lithium-ion flashlights (18650 / 21700) outperform AA lights so significantly in runtime, brightness, and efficiency that they are the better choice even for prepping.» CMV — what scenarios still make AA flashlights the better option, especially for preparedness?