Battery BS Detector: 5 tips to beat the hype

ImageAlmost every media story you read about breakthroughs in battery technology is wrong[i].

Smartphone charger promises to power up batteries in just 30 seconds. From the well-respected Guardian, both the headline and the accompanying story provide a near-perfect case study in how to critically evaluate these articles, and sort out the hype from the reality.

First, the whole article is misleading. The phone being charged in the accompanying video is a Samsung S4, which of course comes with its own standard battery. And if the demo showed that you can take an existing smartphone battery and charge it in 30 seconds, then that would indeed be a ground-breaking advance! But that isn’t what is happening: the company behind the video is an Israeli start-up called StoreDot, and the 30 second charge is only possible with their charger and their proprietary battery.

Leaving that aside, is this a potential disruptive change in battery technologies? No one knows the answer to that yet, but here is a list of some fairly important questions that StoreDot (or any company that wants to gain significant market share in the energy storage market) needs to answer first.

  1. Neither the video nor the company website gives the capacity of the battery being charged. The standard Samsung S4 battery has a 2,800 mAh rating. If the StoreDot battery has the same electrical capacity, then a 30 second charge time is very good. If it is 100 mAh then that is much less impressive! Talking about charging time without indicating equivalent capacity is very misleading.
  2. If you have every taken off the cover of a modern smartphone, you know that there is no extra room inside the case. It is hard to tell from the video, but it looks like the battery for the phone being charged protrudes from the case: it is physically much larger than the battery it is trying to supplant. Once again, this is potentially a deal-breaker. Anyone who claims to have invented a new battery technology MUST be able to make it fit into the existing space envelope of today’s devices. (There is no reason why StoreDot batteries should be any heavier than convention Lithium Ion batteries, but if they were that would be another problem. Battery weight is a critical design factor for smartphones.)
  3. To keep this post as short as possible, I am going to lump a group of other key battery attributes together. It is good that the StoreDot battery can be charged up quickly. But what about letting go of the electrons: can it efficiently put out small amounts of power, or large amounts (at a high rate) when needed? Also, there is something called self-discharge: Li Ion batteries used to be quite bad at this, and even a week or two would see them lose all their charge. Are nanodot batteries better or worse at self-discharge than existing state-of-the art batteries? Do they work well in the usual +30C to -30C temperature range that smartphones need to operate in? Do they have any odd memory effects, and have problems if they are fully discharged, or not fully recharged? Are they as prone to fires as other Li Ion batteries are? Perhaps most importantly, how is their life-cycle? There have been other fast-charge solutions in the past, and even when they worked they tended to make the batteries wear out much sooner than the average consumer would tolerate. And remember that all of these attributes need to be tested over time (not hours, but years) and across multiple manufacturing lots.
  4. Speaking of which: can this new battery be made at commercial scale? All the issues in point 3 are important, but scaling up to industrial production has killed more novel battery technologies than anything else. Let’s say the average smartphone takes a 1,500 mAh battery, and the average tablet is around 3,000 mAh, and the average laptop is around 4,500 mAh. (That’s not even getting into the demand for Lithium Ion batteries for electric cars, which is over half the market going forward.) There will be around 1.25 billion smartphones made in 2014, about 300 million tablets, and 200 million laptops, for an equivalent of 2.5 billion 1,500 mAh batteries. This video is a bit dated, but existing Li Ion batteries are made with some remarkably low tech processes: a lithium salt is extruded, and thinned through rollers, laminated and layered. I am sure the scientists and founders at StoreDot believe that their process can be scaled up, or they wouldn’t have started their company! But until that actually happens, scepticism is necessary.
  5. You probably saw this one coming, but: how much does this cost? I can go online and find a replacement 2,800 mAh battery for C$11.99. That’s not the cost of manufacture, that’s retail! Novel battery technologies, in their early days and before they achieve the economies of scale, tend to be more expensive, often 10-20x as much. Even 2-3x the cost can be a big deal.

Building a better battery for a smartphone is about making choices. Charging time is one of the variables that manufacturers and consumers would like to improve. But it is only one attribute, and in this space  a gain in one characteristic is usually a loss in another, or many others. And if better charge times lead to less capacity, higher price or shorter lifespan, then this technology is unlikely to ever see the light of day.


[i]Maybe not every media story, but many of the ones that I see, anyway. I remember when the media started talking about biotech, and they tended to be insufficiently familiar with the challenges of clinical trials, animal models, and so on. They are much better today, and the writers will get better about energy storage too. But for now, every article I have seen is more wrong than right.


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