Why your outdoorsy friend suddenly has a gummy bear power bank

Why your [ultra-light hiker] friend suddenly has [the world's lightest] power bank.

I remember Colin Fletcher, years ago, writing in The Complete Walker about trimming the borders off his paper maps to save weight, which seemed like an insane over-optimization to me. But then, I'm not an ultralight hiker.

I am impressed folks are getting their loads down to 10 pounds though.

That insane over-optimization is how folks are getting down to (and below) 10 pounds.

I'm not even remotely an ultralight backpacker, but I do count ounces (no matter what your weight limit is, you can't escape making tradeoffs to stay within it). Your hiking load is a great example of how quickly apparently insignificant quantities can add up. Saving fractions of an ounce multiple times gets you large savings far more quickly than you'd think.

I'm down to around 10 lb base load. And then I hike in the desert where I carry 5 - 7 liters of water (11 - 15 lbs). And food. Saving a pound here and there is totally worth it, but there's a large part of the country where prudent hiking means the majority of your weight is water.

If saving here and there is worth it, why would a hiker carry a 300g battery? Imagine the savings from leaving that boat anchor at home along with whatever obviously non-essential gadget wants to be recharged.

I don't carry a battery, but I do carry a solar panel that weighs around 300 g. I use my phone when backpacking as a GPS receiver, map, flashlight, and eBook reader. Phone + solar panel weighs less than paperback + paper map + flashlight, gives me more flexibility for adjusting plans, and doesn't leave me out of novel after a few days.

I have tried my luck with portable solar panels, and my conclusion is that in most cases, they suck.

For a solar panel to be useful you need:

- At least a few days without access to electricity, otherwise even at max power, you won't get as much charge as a similarly sized power bank

- Good sunlight, preferably in the summer (more daylight)

- No shade, which is the opposite of what you want in hot and sunny summer days

- Correct placement for your solar panel, for example, having it hanging from your backpack will only work if you have the sun in your back

- A large enough solar panel, these tiny panels you sometimes find on power banks are useless

- Compatible devices. Solar panels have a variable power output, not all devices support it, some of them just shut down charging. Your best bet is to use a compatible power bank, but that information is not often specified. Test it beforehand!

My experience with a solar panel is from two week-long music festivals in the summer, which would be almost ideal conditions. My experience was that over the course of a week, I got about the charge equivalent of a 10Ah battery from my solar panel (rated 10W, 300g), so about half the efficiency of that gummy bear battery, for the reasons cited earlier. Maybe I could have done better with a better panel and better planning, but I'd rather have a battery, much more convenient, and cheaper too. I want to enjoy the festival, not babysit my solar panel.

So I'd say you need at least a week without electricity in the best conditions to make a solar panel worth it, preferably more, which I believe is rather uncommon.

Also, I am talking about these portable <1kg solar panels. The large solar panels that go in your car/van are another story.