I saw a similar hydrogen fuel cell USB charger before. It looked interesting, but in practice it was an extremely niche application.
10W peak output could charge an iPad, but they don't specify how long the peak output can be sustained. (In the FAQ they supply only the continuous 2W rate). 2W continuous output will take 5 to 8 hours to charge a modern smartphone, and a day or more to charge a 10" tablet.
The fuel density may be somewhat overplayed as well.
On a full charge of the kraftwerk what is the equivalent capacity in mAh as those in power banks?
It's no powerbank, thats why it's not easy to compare. The energy stored in the fuel are for 1.4 oz (40 g) about 56 Wh and for 8 oz (225 g) about 315 Wh.
Butane's thermal energy density is 13.6 Wh/g, about a third of the thermal density of petrol. It's not clear whether 56 Wh means the electrical energy produced by the cell or the total device capacity that can be replenished by the cell (i.e. before or after device charging losses). At any rate, 56 Wh/40 g = 1.4 Wh/g, so about 10% efficient at whatever point they list.
A full cartridge weighs 80g and holds 40g of fuel (56 Wh). The fuel cell device itself weighs 160g empty or 200g full.
Worst-case comparison vs batteries is comparing the device alone. The device can charge a small smartphone (iPhone 6) perhaps 6 times, or a large smartphone (iPhone 6 Plus / Galaxy Note) perhaps 4 times.
A $40 59 Wh
16000 mAh battery pack weighs approximately 300g and costs about $40. A "refill" costs about a penny and takes about 8 hours to charge with 5V 2A USB. The battery pack is also about the same size as the fuel cell - narrower, thinner, and longer.
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A more favorable comparison for the fuel cell would be say a month long camping trip where you charged an iPhone 6 say once per day. This would require the fuel cell ($100) and 4 additional cartridges ($15 = $3/cartridge + 1 in the device), for a total of 520g. Alternatively you would need 5 16000 mAh battery packs ($200), weighing a total of 1450g.
Of course, if you're going to be out in the field that long and you have sunlight available, maybe solar charging would work better. Why not a $30 390g
8W solar panel and a single battery pack? That panel will charge a $26 135g
6400 mAh battery pack in 5-6 hours of direct sunlight, and the battery pack could charge the iPhone 6 a bit over 2 times at night, so you would have some flexibility for cloudy days.
Note if lighting is more inconsistent, or you are walking under shade trees, then you may need to use a larger panel. The niche applications for the fuel cell are in environments where lighting is inconsistent or unavailable, or where the fuel needs to be stored for a long time.
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It's worth evaluating their other claims too.
One filling supplies enough energy for 11 iPhone chargesPledge $49 or more
ECO-FRIENDLY PACKAGE! Get 12 cartridges (2,16 lbs) with renewably produced LPG. The LPG is produced by conversion of renewable power to gas (P2G). This means one year of freedom! (compares to 275 full iphone charges).If the 56 Wh in the FAQ means charged device energy, and they mean a pre-6 iPhone, then this claim bears out. If they mean the USB outlet delivers 56 Wh (5V 400 mA for 28 hours) then this will only charge an iPhone 6 about six times (approximately 4.5 hours per charge).
I assume the 275 full iPhone charges is a mistake - that's 23 charges per cartridge, which doesn't line up with their 11 charges per cartridge or 56 Wh claims elsewhere on the page.
Extremely light refill cartridges - 20 times lighter than batteriesBeing generous - let's assume the 11 iPhone 5S charges above is accurate. Given an 80g cartridge and ignoring the fuel cell, this gives about 7g per charge.
The least dense modern anker device is the 3200 mAh single 18650 battery bank. 80g will charge an iPhone 5S approximately 1.5 times, so about 53g per charge. Only looking at the kraftwerk cartridge, the cartridge is about 7.5x as light as an equivalent battery.
If you look at a denser battery pack, like the 300g 16000 mAh pack, it will charge the iPhone 5S about 7.5 times, or 40g/charge. Now the cartridge is only 6x as light as a battery.
And as shown above, the fuel cell adds significant bulk and weight.
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So where does this make sense?
It's expensive. Not counting the $100 device, each iPhone 6 charge costs between $0.30 and $0.50. And their butane is priced about in line with other butane sources I found online. Charging an iPhone 6 directly from the wall will use about $0.001. So you're probably not going to use this to charge every day.
It's low-power. Modern tablets are more power-efficient than they used to be, but this will take most of a day to charge an iPad Air. The tablet will actually discharge while the screen is on and it is plugged into the fuel cell. A large smartphone (iPhone 6 Plus / Galaxy Note) might do the same.
The fuel cell itself is bulky and heavy. It only becomes lighter and less bulky than USB battery packs once you need a very long operating period. Say 5+ smartphone charges or 20+ hours of operation at 2W. So you need a long period of off-grid operation.
As mentioned above, small-scale solar makes more sense if you have ready access to direct sunlight for part of the day. So this might work better for a long caving expedition perhaps, or for operating indoors where grid access is not guaranteed, deep sea diving, or conditions where it may be very rainy or overcast for long stretches.
Butane is pretty easy to store, and available at most gas stations. I'd be hesitant to rely on a kickstarter fuel cell in a true disaster, but barring device failure this should supply power regardless of weather / grid conditions. So there's that.
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Topic: Butane Fuel Cell USB Charger (Read 2062 times)