StoreDot Ltd. (Ramat-Gan, Israel), a startup developing quantum dot technology, has a put a video on YouTube that shows the company's technology being used to charge a Samsung smartphone in 30 seconds.
The video has been viewed 1.9 million times in a couple of days and has generated much excitement. However, it comes with no commentary or explanation – and doesn't add up for me.
The technology appears – courtesy of an icon on the display – to take a Samsung smartphone from about 25 percent to 100 percent charged in 30 seconds. The phone has a black box strapped to its back, which is the prototype battery developed at StoreDot.
Now you might assume that the prototype battery, although bulky because it is a prototype, would hold the same amount of charge as the standard battery to make any comparisons drawn equitable. Never assume!
An email conversation with Daniel Aronov, vice president of R&D at StoreDot, provided this additional information: "The FlashBattery is a new generation battery that is based on proprietary multifunction electrodes (MFEs) that charge like a supercapacitor and discharge like a battery. We are modifying the material of the electrodes with our bio-organic multicomponent nanomaterials to create pseudo-reactions and increase Li-ion uptake that add capacitance to the electrode. In parallel, we optimize the electrolyte with small bio-organic molecules in order to have multi-peak pseudo reactions."
That sounds good and quantum dot-like but lets get to the math, which is where things don't add up.
A Samsung lithium-ion battery for a Galaxy S3 is rated at 2100mAh. So it would take 2.1A flowing for 1 hour to fully charge it. And to charge it in 30 seconds would require an unfeasibly large current of 252 amps!
So I asked Aronov what is the charge capacity of the prototype FlashBattery. "FlashBattery is equivalent to a battery of about 700 to 800mAh, that is one third of standard Samsung Galaxy S3 battery," he said. I also asked what the maximum current was during the demo, to which he responded: "The maximum current we use during the charging is about 30A."
Putting aside the fact that the FlashBattery was not completely flat when it started charging that still leaves me out by about a factor of three.
1A = 1 Coulomb per second
1Ah = 3600 Coulombs
30A flowing for 30 seconds is the movement of 900 Coulombs of charge.
900 Coulombs is equivalent to 250mAh – and 250mAh is not 750mAh.
I put this to Aronov at StoreDot via email and he said there is no flaw in my calculations but that FlashBattery stores energy equivalent to that which a 800mAh battery would.
What?
Sure, there are things you can do changing the capacitance and voltage but you can't get more energy out than you put in. When I pressed him with conservation of energy arguments, he responded with: "We are currently in the process of filing patents around the power management properties of the FlashBattery, so we cannot provide all the details."
So I remain a factor of three adrift and in the absence of engineering detail that squares this circle for me I remain to be convinced.
Not without merit
However, that does not mean that StoreDot's FlashBattery technology is not without merit.
If it charges at high levels of current, such as 30A, then it will be able to charge much faster than a conventional lithium battery – but you better watch out for tripping circuit breakers in your home. If the current is limited to lower values then charging the phone will take proportionately longer and be proportionately less advantageous. In which case we are probably talking of a charge time measured in minutes rather than seconds and a bit long for a YouTube video.
One thing this YouTube video does demonstrate is that if you put a smaller than standard battery behind a cell phone you can charge it up more quickly than the standard battery! Who would have thunk it?
Company founder and CEO Doron Myersdorf has been quoted saying he expects to put a StoreDot battery into a smartphone within a year and have a commercially ready device within three years.
StoreDot was founded in 2011 to develop peptide–based quantum dots originally discovered at Tel Aviv University. Quantum dots are nanometer-scale crystals where the physical dimensions allow quantum mechanics to effect the electro-optic properties. Tel Aviv's contribution was to spot how peptides, biological materials, could also impact quantum dot performance.
Because the materials are tunable, the range of behaviors is wide and StoreDot says its nanodots could be used for a variety of things including displays, non-volatile memories, image sensors, as well as batteries. The company has also been reported to be in talks with Samsung with regard to its quantum dot technology and, clearly, there are many smartphone opportunities there.
However, such YouTube videos serve to remind us that peer-reviewed technical papers remain one of the best ways to disseminate scientific and technical knowledge. YouTube is good for entertainment – and getting publicity.
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