Even just going by the USB specification, the lowest that it allows is 4.0, and that’s in USB 3.0 – earlier versions have higher requirements. If I remember correctly, 4.5 V is USB 2.0 – and that’s the requirement for the device to operate, not charge! Charging is fundamentally limited by battery voltage, unless the device itself upconverts the voltage it receives – but why would it do that, if the spec is intentionally designed to give it voltage high enough to charge? Now, with cheap USB portable solar chargers specifically, I can believe that they are undervolted – this would mirror my personal experience with them being basically useless in anything other than direct sunlight, and weak even then. I have one sitting outside right now, actually, for almost a week straight – and it can’t get past 40% charge on the indicator. If a fully discharged Li-Ion is 3 V, and a fully charged one is 4.2 V, then 40% would be at about 3.48 V. A charger that’s outputting around 3.8 V could realistically get it to that point, accounting for cable and connector losses. You should try this experiment with those chargers that you’ve measured – take a few fully discharged devices, and see how much they can get charged before they flatline. If a charger can only get something to 30-40% even in the best conditions, that’s an important thing to know, IMO. However, this is for solar chargers, and I presume the reason is because they don’t bother with a stepping circuit. USB power banks should never do this. What you should see when measuring voltage is mostly steady, gradually decreasing output within the allowed limits, until the very end, when the internal battery voltage is so low that the stepping circuit can’t do anything about it – then the output starts falling very suddenly and rapidly. This might also depend on the current. I know that cheaper ones are often undervolted under load – so they advertise 5V/2A, but in reality it’s more like 5V or 2A. This is why some are unable to charge powerful smartphones at all – the smartphone negotiates the highest current that it can get, and then draws that, but the voltage isn’t high enough for it to use that.
Also, in the updated verbiage, you cite Goal Zero Sherpa as an example. If Sherpa actually outputted 3.89 V, as you claim, it couldn’t charge anything, because most USB devices won’t charge below 4.5 V in practice. The reason is that a fully charged Li-Ion battery goes to ~4.2 V (and a fully discharged is ~3.2 V – 3.7 V nominal is the average between these two), so you need voltage higher than that – after accounting for losses in the cable and the connector – to charge it. Of course, this has nothing to do with voltage output. The internal nominal battery voltage of Sherpa is 3.79 V, if you divide their mAh rating by Wh, but like any other cell-powered USB power bank, it then upconverts that voltage to ~5 V that USB requires. And yet you specifically claim that “most of the USB battery packs and solar panels we’ve tested in the lab also meter at just under 4V at their USB ports”. Would you care to share more details about said testing – which USB battery packs and solar panels (even just a few more names), what voltage meters have you used etc?
The point here is that the notion that voltage of output ports is what matters is fundamentally wrong – nobody measures it like that, so it’s not good even as a ballpark measure. If you go with this method for USB power banks, you are overestimating the ideal capacity by about 30% – and that’s before you account for conversion losses etc. And then you have the ones that can produce very different output voltages – especially common in larger power banks and the so-called “solar generators”, but increasingly common in general with the adoption of USB QC and USB-C with its variable voltage. These days, you can see power banks that can do 5V, 9V, 12V, 16V or 20V on a single port. And bigger ones sometimes also have an AC socket at 110V. How would you even apply that method to such a thing? The nominal battery voltage for Li-Ion cells is always 3.7 V, and minor variations of that is what’s used for pretty much all consumer battery packs, so it should just be assumed when it’s not specified. Anyone using anything different will specify it (and usually also give Wh numbers). So the ballpark for mAh -> Wh conversion is to multiply by 3.7.
The vast majority of USB power banks on the market give mAh ratings that have nothing to do with the voltage of either input or output ports. Instead, they use 3.7 V – i.e. the nominal voltage of the Li-Ion battery inside, before it gets converted to 5V for USB etc. The reason is simply that it allows them to use larger numbers. So, a 5,000 mAh battery with a USB port on it is not 25 Wh, but rather 18.5 Wh.
With Hatsan 135 QE, confusingly, it appears that there are both spring and piston versions of it, and the piston one is actually more common (the spring version is older). Vortex is the piston version specifically. The spring model is the one that doesn’t say “Vortex”.
It would be great to see a write-up on specialty cords made out of much stronger but lighter materials: Kevlar, Dyneema etc. There are some interesting trade-offs there that are not at all obvious (e.g. tying knots…). A detailed hands-on review like you guys do would be extremely useful – especially if it also compares them with paracord, seeing how it is a de facto baseline for prepping cordage. The main reason for the interest is that weight is always at a premium for any kind of a get-home bag. Lighter cordage can save on weight and bulk – or, alternatively, one can carry more of it for the same weight.
Behemoth is interesting is that they are lit exactly like matches. It’s basically Sweetfire with a match head, so far as I can tell.
They aren’t technically matches, but did you by chance look at UCO Behemoth? It looks like a perfect combo of a match and a firestarter…
Buy some Wolf Gold .223, chrono it, and then get back to us on that “higher velocity” thing 🙂 It’s not that there’s no difference, but it’s nowhere that simple.
Same reason why you might prefer a fixed knife over a folding knife. In practice, I found the difference to not be as big as it seems (it has a shorter handle than a typical folding saw, although it’s still plenty big to hold even with large hands). And it’s still way lighter than e.g. a hatchet, which many people do use for bug out as well.
Silky also makes Gomtaro, which is a non-folding saw designed to be carried in a belt sheath (but can just as easily be strapped to a backpack etc). So it’s still portable, but fixed blade will likely be more sturdy than folding saws. https://www.amazon.com/102-…