> Well it happened in the solar module market[1].

What is "it" that happened? If you are talking about sustained exponential cost reductions over a period of decades, like Moore's law, then maybe it did happen from a very high starting cost, but it won't continue.

Any market can undergo a rapid reduction in prices over a short period of time, as a product increases in adoption by one or more orders of magnitude.

You could fit an exponential curve to that growth, but ... it will almost never be sustained. The future is what we are talking about here.

Let's take solar modules as an example. From something like [1] prices have dropped from about $4.00/watt to $0.30/watt in 10 years. So that's a price drop of about 23% per year (each year is 0.77 the price of the previous). So today, at 30 cents/watt a 300W panel (the big ones you see on houses) is about $90.

If that is really a sustained exponential drop, those same panels will be $6.75 in 10 years. Possible? Yes. That said, I don't think you can find almost anything that big and heavy almost anywhere for $6.75. Maybe bricks or gravel or something, I'm not sure.

10 years later, those same panels will cost 50 cents. Possible? No way. You aren't going to ship a 300W panel anywhere for 50 cents. You aren't going to have space in your warehouse for something that big for 50 cents. You aren't going to be able to buy even the basic raw materials like glass and aluminum for 50 cents.

There's a common theme here: for something to scale exponentially, at a fixed size, every part of the process has to scale exponentially. The cost of shipping was irrelevant when the panels were $1,000, but it becomes pretty important when you are trying to ship something that weighs 100 lbs across the world or even a country and sell it for less than a dollar. The basic raw materials are a pittance with $500 panels, but they dominate the cost if you are trying to sell them for 50 cents.

The only way this exponential scaling works is if you can make something roughly the same size exponentially more efficient. That's that happened with CPUs. The CPU itself was more or less the same size for decades. They made them in similar fabs. There were some "traditional" efficiencies of scales thrown in, like moving from 200mm wafers to 300mm wafers, but the only thing that allowed exponential improvement was that the chips themselves became a million times more efficient without increasing in size or (mostly) the consumption of any raw material.

CPUs didn't scale up a million times by building a giant fab the size of a country, and using wafers miles across and mining silicon from the moon, which would be how a traditional process would scale up: they scaled up by becoming internally a million times more efficient.

Solar cells don't have that type of scaling available to them. There are hard limits on the efficiency (which is already above 20%) based on the physics involved - but even without any reference to cell physics there is a hard limit at 100% which means the efficiency upside is at most a one time 4x gain from here.

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[1] https://commons.wikimedia.org/wiki/File:Price_history_of_sil...

Oh come on! No one here, other than yourself, has tried to claim that exponential cost reductions will continue indefinitely. But it is a fact, that solar experienced that type of cost reduction for a period of 2-3 decades. It's very unlikely to continue on that trajectory, but it doesn't really matter because solar is now one of the cheapest forms of generation on the market at this point.

Batteries are in a similar position as solar was a decade or two ago. The grid operators desperately need storage capabilities, and li-ion is one of the more promising solutions, but it's still too expensive. But another decade of cost reductions can change that. No one knows for certain if it's possible, but like I said in my original post, no dramatic technology changes are really needed, just better logistics and scaling could be enough.

> Oh come on! No one here, other than yourself, has tried to claim that exponential cost reductions will continue indefinitely.

The OP did, which is what I was responding to. He mentioned the current exponential decrease in battery costs, and said "I see no reason for that not to continue".

They then drew a direct analogy to Moore's law to explain how such exponential gains can be sustained. I disagree.

Of course, even the GP probably agrees they won't continue "indefinitely" but my claim is that they can't even continue for very long (the higher the rate of cost reduction, the shorter it can be sustained).

> But it is a fact, that solar experienced that type of cost reduction for a period of 2-3 decades.

Kind of, there were certainly long periods of stagnation in solar panel costs, but also periods of large drops. It also depends how your pick your starting point.

One has to ask (as you did) whether today's batteries are more like the low-volume niche product of 70s solar panels, or more like today's solar panels. I'm willing to bet the latter, both because batteries have seen substantial investment to date (I'd wager much more than solar panels), and because the existing scale of battery manufacturing is already massive (c.f., gigafactory). Furthermore, there are no apparent revolutions in battery technology on the horizon.

So rather than being at the start of a precipitous drop in battery prices, I think we are somewhere near the middle, and the drops from here will mostly slow down not speed up.

That is a fair point re existing battery scale. However I would counter, that to date, the vast majority of that development and investment has gone towards batteries for small devices (phones and laptops, basically). Compared to utility scale battery packs (and to some degree electric vehicle packs), I imagine the manufacturing challenges are very different. For comparison, the battery in my phone is about 13Wh, whereas the Tesla battery in question is about 130MWh, 8 orders of magnitude bigger. And we have only very recently started building systems like that. While a 10x reduction in cost certainly might be a stretch, I wouldn't be surprised to see at least a 50% reduction in the next 5-10 years.

You might be right about these large scale systems.

Are they using significantly different technologies for the individual cells? I always found it weird that the large battery in a Tesla, for example, was just made up of thousands of 18650 cells that are probably smaller than the battery in your phone. Is the Powerwall is the same?

Does it get any different at larger sizes? Obviously stuff must be different outside of the cells, even if the cells are the same.

This is just based on my memory, but I think they use different battery chemistries but use the same cell size (18650). I also thought it was weird that they were using 18650's when I first found out about it, but I think the need for thermal management actually makes the smaller cell sizes ideal.

Of course this is also why I think there are some cost reductions on the horizon, as current EV and grid tied batteries are basically just a bunch of laptop batteries thrown into a fancy box.

> but I think they use different battery chemistries but use the same cell size (18650)

I also read something like that. I suspect it is more of a tweak than anything major. No doubt it is the same basic chemistry but perhaps with minor tweaks to the various ratios and material thicknesses and so on. The Tesla batteries are a single-application cell, so you know exactly the maximum discharge current, the maximum charge current, the temperature parameters, and so on, whereas a generic 18650 has to balance those for a "typical application" or whatever. See for example the Samsung high-discharge INR18650 cells which trade off capacity for higher max discharge current.

OTOH the other hand I also heard the early Teslas were using exactly the Panasonic 18650B cell. They could both be true: maybe it was a stock cell in the early days and they tweaked the formula later in concert with Panasonic as their volumes rose. There was no big evident spike in capacity vs weight though...

> as a product increases in adoption by one or more orders of magnitude.

/aside With world human population forecast to decline, efficiences and economies of scale will be less in the future.

The real reason we need strong AI - as consumers.