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With the recent disastrous weather, a lot of people have lost power for many days and are looking to be more prepared for the next time. Generators can help on a large scale, but not everyone can practically use them (like most people in apartments), and the portable ones are only good until you run out of their fuel. But more importantly for this post, I don’t know anything about them, so I’ll assume you don’t have one.

If you just want to charge an iPhone,¹ I can be a bit more useful. Here are your options:

Most extended-battery iPhone cases can only provide a partial iPhone charge before they’re depleted. Some of the very large external brick-like packs are worth up to two or three charges. But that’s about it. These can carry you through a power outage for a day or two if you’re lucky, but probably less, especially if you’re using your iPhone a lot because you can’t do much else.

This hand-crank charger (via Daring Fireball) sounds like a good idea but probably isn’t, and it probably isn’t worth $60. While your hand-cranking power is “renewable” and effectively unlimited, it’s probably going to take a lot of cranking for a full iPhone charge. (I can’t find any specifics on it, unfortunately.)

The PowerFilm solar AA charger uses unlimited, renewable, free solar energy. But it’s very slow: it takes many hours of strong, direct sunlight to charge a pair of NiMH AA batteries (the most common rechargeable type today), and they’re only good for about half of an iPhone charge through its USB output port. I got one of these for a group camping trip a couple of years ago as an unlimited-capacity last resort, but we didn’t use it much because it was too slow. It’s also probably not worth $70.

The standout hit of the camping trip, by far, was the Tekkeon AA-battery USB charger. It’s built cheaply and doesn’t even feel like it’s worth $20. But you can get nearly two full iPhone charges from a set of four AA batteries, if you use the right kind. The obvious disadvantage is that you’ll eventually run out of batteries, but you can get AA batteries nearly anywhere, even in bad-weather panics (since most old flashlights use C and D batteries), and you probably already have a bunch of them lying around.

The type of AAs matters a lot, since it’s a high-current device able to drain its AA batteries within an hour or two. I did some tests with different batteries before the camping trip and found that standard alkaline AAs don’t get very far at all, but NiMH rechargeables are passable, and (non-rechargeable) lithium AAs are the best by far. Lithium AAs are more expensive than alkalines, but they’re perfect for stockpiling for this sort of use: they have extremely long and stable shelf lives, they don’t care what temperature it is, and if this matters to you, they weigh almost nothing. (And if you get to the store after everyone else has already panicked and bought their supplies, they’ll be the only batteries left since they’re the most expensive.)

If I had $70 to spend on this problem, instead of a hand-crank or solar charger with a tiny capacity, I’d rather have the Tekkeon AA box and 40 lithium AAs, which could power my iPhone for about a month of frequent use. If I actually lose power for an entire month and burn through them all, presumably I will have spent part of that month finding some way to get a few extra AA batteries. And if that’s not possible, I probably have much bigger problems.