Solar-charging battery for USB devices with massive 20000mAh


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Li-ion batteries don’t like heat. I wonder how long they last if you leave them in direct sunlight all the time.

That’s pretty cool. They should integrate a wireless charger into that thing so you can just lay your phone on top and…um…oh right.

(This it’s what actually went through my mind upon seeing that photo.)

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I was on the fence, but the product listing says that it’s “anti-explosion,” and I’m kind of a sucker for non-exploding products.


Hmm. Any electrical engineers out there who could estimate how many days (weeks?) it would take to charge that battery “with just the power of the sun” using that little solar panel?

It’s probably a good thing it can also be charged up by plugging it in.

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Sure, but exploding products have a certain appeal too.

I see this comment at amazon:

I get about 2,000mAh worth of charge in about 6 hours.

Edit: the product description has this:

SolarJuice can charge your iPhone about 50% power for emergency after being solar charged for 8 hours under normal sunlight
Which sounds like about half of what the customer was estimating.

What’s with all the big numbers? 20AHr or 100WHr not so impressive, huh?

I’m somewhat amused with the current trend for a tiny battery with not enough life in your device and a big fat heavy battery in your pocket or backpack to charge it up again. Just duct tape it all together, I say, and get an upper body workout at the same time.

I’d like to set up a solar panel or two on the back of a backpack to simply keep some of these always topped off over time in case of emergency.

The problem is (while mountain biking) I tend to fall and roll over on my backpack and I can’t imagine the panels would survive it.

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You’re gonna hate the new sodium shower-shoes I sent you.

Are you Benny Hill?


Go for rubidium or caesium, these are more posh. Sodium is not only for peasants, it also just hisses and burns and doesn’t explode so much.

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I don’t know if you’ve hiked much, but when I was in Scouting, the conventional wisdom was: If you know you’re gonna fall, try to fall backwards onto your pack.

The reasoning: Your hiking pack has a lot of wonderful padding, it braces your spine and hips and you’re securely harnessed into it. Also your pack is heavy. I’d rather tip back and land on the buffer of the pack, then tip forward and first get mashed into the ground, then be possibly stuck underneath it. Especially if we’re doing something like a month long backpacking trip and we’ve got really heavy packs, which sometimes were ~100 LBS.

Sodium explodes just fine. a silver dollar sized piece dropped into a beaker of water will go off like an M80 if it’s dropped in quick enough, instead of just sprinkled on.

Yes, but it is still a peasant variant of explosion in comparison with the alternatives.

Using Det cord ruins it. I can’t tell how much of the explosion is cesium and how much is the det cord. Invalid contaminated experiment. I wanna see one where they mechanically rupture the ampoule under water without the use of extra explosives.


My ex recto guess is that the detcord did not contribute more than 10-20% of total liberated energy. The range could be calculated by assuming a spherical cow and comparing energy liberated by reaction of known amount of Cs, and the resulting hydrogen burning, with the estimated submerged length of the detcord and the energy liberated by explosion of the corresponding amount of PETN. (On the caesium side, the result of the “naive” calculation will be a bit too high, as there will be losses on not all hydrogen burning and on losses of Cs by ejecting particles from the reaction zone before they get fully consumed. And more mechanisms that can screw up a nice smooth equation when we try porting ideal model situation to hairy real one.)

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I noticed: the bite taken out of the bucket was exactly where the det cord was in contact with it. The direction the bucket moved was also perfectly opposite to the det cord. Also det cord is great at getting everything else moving including the water. I still want to see exactly what it looks like with just mechanical breakage of the ampoule.

Spherical cows not withstanding… Even in Mythbusters they were able to remotely crack a vial of sodium underwater remotely. Just bracing it against a rock in a fish tank, and dropping a metal rod through a guide tube on it using a pulley. No contaminating extra explosives, you get to see the whole reaction instead of just the bucket going “voip”. We’re here to examine and demonstrate the explosive properties of a material. It’s dumb to use a different explosion to set off the material we want to test. That’d be like licking an agar plate before inoculating it with the culture you actually want.


Kvetching accepted as valid. There are other videos on a “caesium explosion” query, with mechanical activation, but they involve significantly smaller amounts of the metal.


I’d certainly be pleased to hear that ongoing improvements to the details of their construction have solved this; but that was going to be my question.

For reasons that would probably explain the state of my study and my wiring closets, I’d be interested in seeing more products that separate the (expensive; but fairly long lasting unless mechanically damaged) solar cell from the rather-more-sensitive-and-born-to-die Li-ion module. Ideally, with some sort of elegant modular wiring harness that allowed you to choose the number of solar collectors based on available space on your backpack/in your window/etc. and number of battery modules based on your weight, volume, and runtime demands; but still have charge/discharge/capacity/etc. data centralized to a single display.

Maybe a higher voltage harness interconnect(48? telco style) to keep the conductor weight down, with DC-DC conversion at the battery pack for safe charging, and an i2c or SPI line so that a single ‘display’ module can report the status of the entire system?

Ooh, that would even allow you to mix-and-match battery chemistries, eg. a Li-ion pack for light weight in a carried pack; but NiMH or lead acid for home backup or vehicle mounted portions of the system.

And then you could extend the ‘display’ module concept with the possibility for multiple slave controllers, potentially connected by other busses(eg. BTLE so you can check whether it’s worth walking over and plugging in your carried modules to the fixed/mounted modules). Also, SNMP, because.

Ok, now I have the nagging sense that I’ve gone and overcomplicated the design…

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This is a good time to remember the rule of thumb that advertising claims are the opposite of the truth (you don’t need to advertise something as having “no unpleasant odor” unless it smells bad); clearly, when the manufacturers think about this product, explosions are not far from their minds.

I am intrigued by how “explosion-proofing” might work in this context. Does it channel all the energy into firing a small mortar round into low orbit?

Actually, thinking about it, that’s sort of a good idea. You just set it up to fire away from your campsite, and the shell could unfurl a parachute reading “HELP-- SEND PHONE CHARGER”

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