Tuesday, October 27, 2015

The Hero with four faces: Part 2

In this post we continue looking at the best-known battery chemistry for each of four metrics of importance:  energy density, charge time, life, and cost, aka, a “Hero” battery.  In Part 1, we looked at energy density and charge time.  Today, we will look at cycle/calendar life and cost.

And oh… there really is another metric that is also important (arguably more important!): safety.  I talk about this metric at the end.    

The cycle/calendar-life Hero:  Many battery people will argue that the Edison battery (yes, that Edison) is the Hero for cycle and calendar (or shelf) life.  And rightfully so.  I have a different Hero in mind, but, I can see why others think of the Edison battery.  I have heard that there are 30-year old batteries that still work!  And they cycle thousands of times, even tens of thousands of times.    

Family heirloom, anyone?

The Edison battery has a nickel hydroxide positive electrode (or, as battery people have been calling of late, cathode) and an iron negative electrode.  The positive electrode undergoes intercalation of protons, which I like (If you want to know why, read “A Brief History of batteries-Part 1 and while you are at it, read Part 2 also); it undergoes no disruptive structural change, although there is lattice expansion that occurs due to the co-intercalation of the water and potassium ions.  There is a side reaction wherein oxygen is evolved throughout the charge/discharge cycle, but, for reasons that I will get into soon, this is not an issue.  This electrode is virtually indestructible. 

The iron electrode undergoes a reaction by which the metal anode reacts with the electrolyte to form an hydroxide layer.  Lithium batteries have a similar reaction, by the way.  The Li metal reacts with the solvent and forms a layer.   Except that the layer is not reversible.  Luckily, the iron hydroxide is very reversible.  So much so, that we can cycle it thousands of times. 

So why are we all not taking to our lawyers about changing our living will to bequeath a nickel-iron battery to our children?  For one, the energy density is kind of low.  Very low!  At 25 Wh/kg, capacitors start looking interesting!  

 There is a second problem.  The battery requires regular topping off with water.  Like.  Every. Week.

Similar to the old lead-acid batteries.  The positive electrode of the lead-acid battery evolves oxygen during operation (so does the nickel-metal hydride battery).  The oxygen comes from water electrolysis.  Any oxygen that is released is removed from the battery via the vents.  A few weeks of this and the water level decreases.  Hence we fill in deionized water. 

Obviously, everyone hated the tedium of opening the hood, opening the vent, checking the density, and adding water.  When I could be using those precious 3 minutes to watch Gotham instead.   The humanity!  (well.. ok, there are some corrosive chemicals to deal with, so don’t try this at home). 

In lead-acid (and in the nickel-metal hydride battery) we solved this issue by “sealing” the battery.  This forces the evolved oxygen to migrate to the negative electrode and recombine to form water again.  Ergo, oxygen comes out, but nothing is lost.  Except electrons.  The battery self-discharges, but no capacity fade is observed. 

Why does this not apply to the Ni-Fe battery?  Because the iron electrode also breaks down the water and evolves hydrogen.  Hydrogen, unfortunately, does not recombine (at least not in any appreciable amount).  So any hydrogen coming out is lost through a vent.  So the water will dry up and you will be missing 3 vital minutes of insert-favorite-activity-here. 

So what do you do with a low-energy density battery that requires constant babying?  You keep it in the basement and bequeath it to you children and hope they forget that you really have nothing of value left.

Or you use it to learn some lessons.  Like, intercalation is good.  Or side reactions (like oxygen evolution) are ok, if they can be reversed.  Or making layers (like hydroxide) is perfectly fine, if said layers are reversible.  Or, water-based systems are very forgiving, and they can be maintained very easily. 

Are the problems in the Ni-Fe un-solvable?  I actually think they are not.  Other systems, like the zinc electrode, have had similar gassing issues and folks found that mercury was effective in poisoning the hydrogen evolution reaction (in addition to poisoning a few other things).  

Or maybe we can automate the watering system (a battery-drip-irrigation system anyone?).

Despite this, I don’t consider Ni-Fe to be the Hero because this system is not that practical, atleast as we know it today. My Hero is a chemistry that is close enough to the Ni-Fe system.

It is the Ni-hydrogen battery. 

This is the battery in the Hubble Space Telescope.  Launched in 1990, the battery operated in space for 19 years after which it was changed during service mission 4.  These batteries cycle 20,000 times when cycled at 50-60% of its full capacity and have an energy density of 75 Wh/kg; close to other nickel-based batteries.  Now that sounds like a Hero to me. 

So why does it cycle so well?  The positive electrode is the same nickel electrode that I like so much.   The negative is an electrode that evolves hydrogen on charge and recombines to form water on discharge. 

Wait… did we not just conclude that making hydrogen is bad?  Like seven paragraphs ago.  Contradiction much?

In my defense, I only contradict myself between posts, not within posts. 

In the Ni-hydrogen cell someone really made lemonade out of that lemon.  They decide to use the gassing reaction as the reaction to store energy.  But then, the question is: How do we store the gas? 

Therein lies the genius of the design: The battery sits inside a pressure vessel.  When the battery charges, the pressure builds inside the pressure vessel, but it stays inside.  There are no side reactions.  When you discharge it reacts right back.  The nickel electrode still has the oxygen side reaction, but this stays within the pressure vessel and recombines.  Nothing is lost.  Like I said, genius.  Of all the innovations in batteries I have seen and read about, this is the one that I’m still impressed by. 

If only we could get our Li-ion batteries to cycle the way of these older systems.

All seven readers of this blog know that there must be a catch with this chemistry.  In this case, it is cost.  Adding the pressure vessel does not help.  I don’t have any hard numbers, but I’m told it is several thousands of dollars a kWh.

Which bring me to…

The Cost hero:  This is a hard one.  But let me start with a few irrefutable facts:
  • All battery companies will drive cost to less than $100/kWh sometime in the future, irrespective of the chemistry.  But, what if the battery is made purely of gold, you ask?  Trust me, it will still cost less than $100/kWh. 

  • This price will drop to whatever-the-number-needs-to-be, to be less than or equal to whatever-is-claimed-by-competing-companies.  

  •  The actual math behind the claims will be guarded in a fashion that would make the CIA proud and will consist of various confusing assumptions related to cost of materials, cost vs. price, claims about cycle life, assumptions about Indians dumping the gold hidden in their mattresses etc.  

Now that we have settled on that, let us talk about cost. 

One can define cost a few different ways: Either the capital cost of the battery or as a cost per cycle (or charge passed) over the life of the battery.  Cost drops with scale of manufacturing (think, Tesla’s Gigafactory) and as this scale increases the cost of materials starts to dominate the overall cost of the battery.  Packs cost more than the cell, but as the chemistry gets more complicated (read, Li-ion) the pack costs are significantly higher than cell costs compared to simpler chemistries (read, lead-acid).  And then there is cost and price.  How is one to define a Hero, far less identify one?

The cheapest battery one can buy is the lead-acid battery which costs anywhere from $80/kWh to $150/KWh (and more, depending on the complexity of the system).  Unfortunately, the cost and the cycling go hand-in-hand.  So deep-cycle batteries cost more than backup-power batteries. 

And how long would a deep-cycle lead-acid battery last?  The 8 years and one thousand cycles that some companies promise, or the 5 years and a few hundred cycles that most seem to get?  Too many variables to make a judgment.

Then there is the Li-ion battery where the cost is expected to drop and we are not sure where it will end up.   Three different cost estimates suggest that the costs will hover somewhere between $170-220/kWh at the system level.  So twice the cost of the lead-acid, but with twice the life?  Assuming that the predicted cost reduction pans out.  And will lead-acid also drop in the same time?  Probably.    

Considering where Li-ion battery costs are today (at $350/kWh or more), one could call the lead-acid battery the Hero. But let us wait for 5 more years and revisit this.  We are living in a very interesting time indeed! 

So let us forget about identifying Hero’s and let us get down to things we can learn. 

It helps to have cheap materials.  Things like zinc, carbon and manganese are good.  Lanthanum-nickel alloy and cobalt oxide, not so much. 

But we cannot get too carried away with this either.  One of the cheapest batteries, from a materials perspective, should be the sodium-sulfur chemistry (the cost of these two materials would in the cents/kWh range).  But to actually make the sodium and sulfur work in a battery setting requires solid conductors and high temperature operation.  The final cost: $400/kWh or more! 

It helps to have aqueous systems: the manufacturing is simple.  No need for dry rooms.  And there is a certain amount of system-level advantages to be gained when complex pack designs and battery management systems can be avoided.  So lead-acid-like design and manufacturing would help.

But cost is really cost per unit of energy ($/kWh).  So low energy systems don’t help.  Li-ion stands a gain because of this.  But the advantage of Li-ion (the high voltage compared to aqueous systems) is also the reason we need equipment with high cap. ex. 

If you did not know this already, there is no free lunch. 

These are the four Hero’s.  Each metric has a different Hero (lithium thionyl chloride, lithium titanate, nickel-hydrogen, and lead-acid).  High energy requires high voltage.  This tends to kill the charging capability.  If you want life, it is best to have reversible side reactions.  And cost… what can I say about that one! 

Hold on a second!  Clearly I’m not addressing the elephant in the room.   The one problem that I really ought to be providing insights about and identifying a Hero for: safety. 

A Safety Hero? Well… If you thought cost was hard, safety is even worse.  Batteries are energy storage devices where the oxidizing and reducing chemicals are stored right next to each other.  So asking me to identify a safety Hero is like asking which one of the unsavory characters in Pulp Fiction is the good one (The Wolf?  Haven’t you told your best buddies that you would help them move a dead body?)

I would have said that any system that does not have a flammable electrolyte would help.  But the lead-acid fire at the wind farm at Kahuku, HI would make that sentence a bit hollow.  Clearly, if you work hard at it, any battery can go up in flames!

Having said that, we have been using batteries day in and day out for a long time without anything bad happening, so one can learn some lessons from it.   

Clearly flammable electrolytes don’t help.  Materials that can result in exothermic reaction don’t help.  Bigger the amount of chemicals next to each other, bigger the risk.   So flow batteries will be inherently safer than contained batteries. 

If you ask me for a ranking, Li-ion would be the worst; aqueous chemistries are MUCH better; flow batteries would be the safest.

But safety is not just about fires.  Many flow devices have toxic and corrosive chemicals in them.  These devices have to be contained.

What this all means is that a lot depends on the battery company.  If care is taken to make the battery safe, they can be made safe.  But that costs money.  Companies that pay attention to this and spend the money to do it will find ways to keep the battery safe.

Summary:  So what do our four (or five) Heroes teach us?   That buying a battery is like buying a house; you have to compromise. 

Remember the Third law of batteries from my blog post The Three Laws of Batteries (and a Bonus Zeroth Law):  “Of the four metrics that batteries are graded on for a given application (i.e. performance, cost, life, and safety), typically, only two can be simultaneously achieved. If the battery is designed to also perform satisfactorily on a third metric, it will fail spectacularly on the fourth.”

That about sums up the dilemma. 


Saturday, October 24, 2015

All you wanted to know about batteries. In 140 characters.

I'm working on Part 2 of the Hero blog post.  Hope to finish that over the weekend.  But in the meantime, I went on twitter for the first time (I've had an account for a while, but never posted on it) for a chat related to batteries.  The good folks at LBNL made a compilation of it.  You can find that here.

Not sure I like the 140 character limit.  Seems to not leave much room for nuances.  But I suppose it is great for quick thoughts.


Tuesday, October 20, 2015

The Hero with four faces: Part 1

A few years ago, when I visited a battery company with a few colleagues, I saw data from the company that was pretty impressive.  Slide 1 showed the rate capability of the battery, which was better than the state-of-the-art; Slide 2 was a calculation of the energy density, which was better than the baseline; slide 3 was cycle life and this too looked impressive; slide 4 was…

You get the drill. 

Suitably impressed, I came out wondering what I needed to polish in my resume to land a job at the company before they went public… when my travelling companion wondered aloud if each slide was from a different battery!

 My colleague had a point.  Most (not all) battery chemistries can be made to perform well for a particular metric.  The trick is getting all the metrics to work out for the same battery. 

Make the electrodes thin to get power; make them thick to increase energy (but at the loss of power).  Increase the voltage to increase the energy, but at the loss of cycle life.  The endless games one can play.  This dependence of battery design, cycling conditions, voltage of operation, etc. on performance is the reason battery companies have been getting away with obfuscation. 

But is it really obfuscation?  A proof-of-concept can be a useful learning tool.  If going to high voltages yields more energy but kills the cycle life, while we know that the voltages being accessed should be possible, then it gives us hope that the problem is not fundamental and that a solution exists.  Given time, maybe we will find it. 

Then again, we have been looking for a cure for baldness for ages.  There is proof that baldness is not fundamental (after all, some are oh so lucky), but that does not mean we will find the answer to that problem either.    

But there is merit in learning about what the best possible system is and understanding why it is the best.  To this end, I thought I would list out the best-known (at least to me) battery chemistry for each of four metrics of importance:  energy, charge time, life, and cost.  Each would be a “Hero” battery; a term borrowed from other technology areas to denote a proof-on-concept that something amazing is possible for that metric.  While each metric has a different “Hero” battery there are probably lessons we can learn from them.  These lessons, I summarize in the end.

The energy-density Hero:  All seven readers of my blog know that Li-ion batteries are the highest energy density secondary batteries one can buy, with energy density in the range of 250 Wh/kg.  But the Hero is actually the Li-thionyl chloride battery, which has an energy density of 550 Wh/kg and is, more importantly, commercially available.  The catch is that it is a primary battery (i.e., not rechargeable). 

What gives?

Typical Li-ion cells have a graphite anode.  Moving from graphite to Li metal (which holds ten times the charge and results in a slightly higher voltage) bumps the energy by 50% without changing anything.  On top of that, the thionly chloride cathode has a capacity of 450 mAh/g compared to 180 mAh/g for typical Li-ion cathodes.  Combine the two and you get something much better than Li-ion.

Imagine a battery with 2x the energy density.  Maybe we double the range of a Nissan Leaf, making it a car that is actually useful (joking, joking, all you Leaf lovers) for the same cost.  Or cut the cost of the Tesla battery by half without sacrificing range, bringing it tantalizing closer to the point where everyone can continue to not be able to afford it. 

Unfortunately, all these will not come to pass because the Li anode does not recharge gracefully while the thionly chloride cathode is not at all rechargeable.  If you want to know why, you have to read my blog post titled “A Brief History of Batteries- Part 1” and “A Brief History of Batteries- Part 2”.  Frankly, everything you need to know about batteries is probably hidden somewhere in these pages. 

To make it rechargeable, you just need to change the anode, the cathode, and the electrolyte (i.e., all the three components that make a battery).  When you do that, the battery now cycles a lot better, but at the loss of capacity. 

So is 550 Wh/kg the ceiling?  No.  There is a lab demonstration of a 750 Wh/kg Li-air primary battery.  This would be a record for energy density.  But as I have alluded to in the past, a one-off lab demonstration does not a product make.  So, for now, we shall call 550 Wh/kg the Hero for energy density.  As an aside, the Li-air battery also does not cycle. 

Reversibility restricts us to certain materials; a constraint when removed, allows high energy density batteries to be made. 

An interesting question to ponder: Is it possible to get batteries that are rechargeable and at least as high in energy as these Hero’s?  

The fast-charge Hero:  One of my funnier blog post was titled  I’ll be back…in 8 hours”.  That post had nothing to do with charging times (then again, this blog is like Seinfeld; its about nothing, as far as I can tell) but the title articulates the problem:  We tend to want to charge our batteries very slowly.

Charge them too fast and we have unwanted side reactions (lithium plating and electrolyte breakdown) that can degrade the battery.  1h charge is doable, 30 mins makes it degrade a bit; 10 mins a lot more; 1 min would basically kill the battery (and kill you from the fire that is creates). 

This is true for most batteries, but it is not fundamental.  Meaning, there is no law that says that we cannot charge a battery fast.  One can design the battery for fast charge.  But the compromise is loss of energy. 

How fast do we really need to charge?  For an electric car, a really smart person (who shall not be named) told me that we needed to charge within the time frame of a restroom break.  Another smart person told me that we needed the battery to charge and discharge fully within the time frame of clouds covering a solar panel.  After a few experiments timing myself on restroom breaks and watching clouds move (I plan to watch grass grow next) we can approximate the charging time needs as 5 minutes.  What can I say: I was having an Austin-Powers-just-got-out-of-hibernation moment. 

The question of the grid actually handling this kind of electricity load is a whole other area of debate, but let us focus on the battery for a second.

Electrochemical capacitors can easily charge this fast.  But they have no energy.  Question is: Is there a battery chemistry that can mimic a capacitor’s charge rate?

There was one system that was kind-of-sort of commercialized that I would consider the Hero in this regard.  This was the Toshiba Super Charge battery, which is rated to charge to 80% capacity in 6 minutes and more than 95% in 10 mins!

Here the anode (lithium titanate) operates at a higher voltage than the typically used graphite anode. This helps because the potential of the anode is far away from the lithium plating potential.  This makes it much easier to charge fast and not worry about plating lithium, shorting, and the ensuing degradation and possible fires.   

But the downside is that the higher anode voltage decreases the overall cell voltage, which in-turn deceases the energy.  The battery has a third of the energy density of a typical Li-ion cell (so a third the driving range).  At 90 Wh/kg and 177 Wh/l at the cell level, it is far, far lower than most Li-ion batteries.  Cost of these devices scales with the energy:  this battery will probably cost three times a typical Li-ion cell!

So… an ideal EV battery for the super-rich-with-overactive-bladder demographic?  

Question is: can we get both high energy and fast charge?

If we want to get there I believe we cannot use thick porous electrodes.   While they are great to spread the current, it seems impossible to get away from the electrolyte losses of these highly-resistive organic electrolytes.  Which means that we cannot have thick bulky current collectors and separators.  But then how do we collect the current (especially if the currents are high, which seems likely with fast charge batteries)?

Should we move to electrodes that are not porous?  This limits the useable energy, unless we use electrodes that undergo deposition. One can continue to deposit the metal on top of itself and so “build” capacity, without the added losses from the porous structure.  This may be an avenue. 

My suspicion is that even if we find ways for the electrodes to accept the charge at that rate, the electrolytes in lithium-based batteries will not have the ability to move ions from one side to the other.  Unless we move toward much thinner separators.   This topic requires some careful thinking.

But let us revisit the question: how fast do we really need to charge? 

If we can ensure we have a 400-mile range battery, this should translate to an approximately 5-6 hour driving time (at 70-80 mph).  Then we may be willing to wait a half hour to charge the battery as we make a beeline to our favorite artery-clogging fast food joint. 

For the grid, if we can use the battery to not just take care of the intermittency, but also to time-shift from peak to off-peak, we can size the battery for the time shift and use the (big) battery for handling the small 5-min intermittency.  Each 5-min charge and discharge would only require the battery to swing by a few percent: easily possible with most systems. 

The catch: both of these would require us to pay for the bigger battery!  But hey, batteries are getting so cheap, and companies are going to give us money when they hand us the battery anyway. 

The cycle/calendar-life Hero:  I know what you are thinking: there is no such thing as a cycle-life Hero!  After all, every battery we own seems to last all of 1-2 years before they crap out.   You must be thinking that our Hero must be a 3-year life battery.

What if I told you there are batteries that last 20, even 30+ years and they cycle 20,000 times (no error there, really meant to have four zero’s)?  And what if I told you that these batteries are not the hybrid car batteries that cycle 3-5% per cycle but are cycled deep, greater than 50% of the capacity per cycle?  And that they are (at least they were) being used day in and day out? 

Imagine batteries that last as long as a solar panel.  Imagine being able to cycle them once a day and make them last those full 20 years with no maintenance.

Intrigued?  Come back next week and you shall learn more.


p.s. the title of this post is inspired by the Joseph Campbell book “The hero with a thousand faces.”  Campbell was trying to point out that all the world’s myths, across religions, shared a Hero figure with similar characteristics.  We will see next week that in batteries there is no one Hero.  We basically have four Hero’s with four faces.  

Monday, October 12, 2015

How many watch batteries does it take to drive a car?

Apparently the Apple watch has a battery in it. What the what! And here I thought that crown thingy was for winding the little sucker.  That was one embarrassing scene at the Apple store when I tried to pull the crown (on the gold one, no less) to wind it.  Skeuomorphism much.   

Jokes aside, when iFixit opened up the watch, I was fully expecting it to be 90% battery.  Surprisingly it is not.   It only occupies 50% of the space (all us battery types are the glass-half-full kind).  Obviously a smaller battery would help make this into a little less of a hulk on the wrist, but clearly Apple has made a compromise: balancing bulk, functionality, and battery life. 

We have come to expect nothing but less from our battery (!).  But why can’t the electronics guys figure out how to shrink the taptic engine, the chips, etc.  We need to get them to pull their weight. 

More than the actual volume of the cell (or the capacity) the energy density tells a more interesting story. The apple watch has an energy density of 450 Wh/l, while typical cell phone energy density is approaching 650 Wh/l.  A whooping 40% more: imagine how many more twitter messages you can get before you have to recharge the watch if they had incorporated the better battery. 

So what gives?

In any battery, the packaging takes up significant space and adds unwanted weight.  You need tabs to pull the current out; you need a pouch made of plastic with embedded metal to keep the battery in (and you so want the battery to stay in, especially when you know what goes into them!) and the moisture, oxygen etc. out.  The pouch has to be sealed and so you have a seal line that adds volume, and so on and so forth. 

As the size gets smaller, it is harder and harder to keep the ratio of the packaging to that of the actual active ingredients in the battery the same.  Meaning, there is a critical size below which one cannot get a proper seal, there is a thickness of the pouch below which one cannot guarantee that they will be impervious.  All this leads to a bigger and bigger fraction going toward the packaging, as the battery gets smaller.  Ergo, lower energy density. 

This is kind-of sort-of the problem I was talking about in my post titled “In batteries, 2+2=1. Actually more like 1/2. Well... maybe a bit less.”  In that post I was referring to the problem of needing extra weight and volume for the current collectors, separators etc., the penalty this imposes, and the difficulty of dramatically improving the energy density of batteries using new materials.  But the same issue comes to play when you go to smaller devices with the packaging being the driver. 

Now imagine going down in size even further, to, say, a contact-lens glucose-sensor that Google (or is it Alphabet now?) is developing.  How does one integrate a typical battery into that?  (make an eye patch and go for the pirate look?)

Which is why Google is going for some sort of wireless power delivery. 

As we start moving toward the world of ubiquitous sensing, the internet of things, and the “quantified self” (and other buzz words that I may have forgotten) where we will measure, and broadcast, how many times we cough in a day, what germs we eject when we do, how many of our neighbors are infected by those germs, and when and where the CDC should come pick us up when the germs reach epidemic proportions, the problem of smaller batteries with more energy density is only going to get more serious. 

So how can we change this? 

Clearly we need to think about other form-factors and chemistries that don’t have the same strong dependence of size on energy density.  Thin film and solid state are buzzwords you probably have heard.  These could be applicable.  One can imagine thinner packaging materials, encapsulated cells versus cells with thick seal lines, stacked cells versus jellyrolls etc.  There are few ideas like that out there that look interesting.  But they are still in early stages and a lot of data is needed for them to be proven out.  This area is ripe for innovation and we are going to see some cool things in the next 2-5 years. 

The problem is that what we see is typically an one-off demonstration that show that one can make a small device, but there is no way to know if they can be mass-manufactured at a scale where they will have an impact and at a cost that someone will be willing to pay for it. 

Solid-state batteries have been around for decades.  But they have never been cost effective to manufacture using the expensive deposition techniques that only make sense as a demonstration of what is possible.  The capex would be massive and the yield unproven.  Not a good sign for a mass-market product like a watch. 

Which brings me to the next interesting aspect about the Apple Watch: the cost. 

No. Not the cost of the gold one (although, the one on display at the Stoneridge Mall with the slightly deformed crown may be available on the cheap). 

We can all agree that when it comes to Apple, cost and price are two very different things.  There have been teardowns of the Apple Watch that suggest that it costs $84 to make.  Others disagree, and argue that for new technologies the cost will be higher.  I don’t have a view one way or another. 

The cost of the battery in the watch, according to these teardowns, is 80 cents.  Yes, you read that right, 80 cents!  (Except for the gold watch where the whole battery is made of gold?  Incidentally, turns out that gold can be used as an expensive, and pretty bad, anode material.)

The energy of the 38 mm watch is 0.78 Wh.  At a cost of $0.80 a pop this comes to a $1000/kWh battery.  Kind of expensive compared to most cell phone batteries, but inline with what one would expect for these small devices made for a niche low-volume application. 

And oh boy!  Are those volumes low!  Rumor has it that Apple sold 3 million watches in 3 months.  Even assuming all of these are the large 42 mm with a 0.94 Wh battery, this is a total of 2800 kWh.  Which would be 33 Tesla Model S, 85kWh cars.   

Sold.  Over.  Three.  Months.   

For comparison Tesla sells 2000 cars a month.  If you work for a battery supplier, which one would you rather sell to?

Turns out, probably to Apple.   

Wait, what?

Ok.  I would much rather have the volumes of Tesla.  Or sell to the MWh grid scale installations that are popping up everywhere (I use the word “everywhere” rather generously).  But when you are selling something that big (read, expensive) margins are going to be pretty thin.  At $350/kWh for an 85 kWh battery, the Tesla battery probably costs $30k.  How much more can a battery company charge? 

But at $.80 per watch, one can afford to ask for a bit more money for something that has, say, much higher energy density.  What is an extra dollar or two between friends when you are shelling out $500 on a timepiece? (or, if you are like me, $10k).

This is the advantage of going after a market where the total cost is small and the margins high.  It provides a path of first entry to the market.   But the scale dwarfs in comparison to the EV or the grid market. 

So can one make an amazing new battery for the watch that has, say, three times the energy even if it costs thrice as much and then slowly make the size larger and larger till one day it drives our cars?


After all, the Li-ion batteries powering every electrified car and most of the recently announced grid installations all started as small consumer electronic cells.  Companies learnt how to make them more reliable, get tighter tolerances, and make them safer so that one day, after 15 years, they were able to move them to vehicles. 

Took a long time, but it did happen.  So there is hope that some new idea would first get implemented in small devices, but would cost more.  In time, the cost will come down and the larger markets, which are more price-sensitive, would become accessible.  Maybe…

Or… one can borrow a page from Tesla, string a bunch of watch batteries together and make an electric car battery with it.  Instead of eight thousand 18650 cells, all one needs to do is take 10 times that number.

Feel free to run with that idea.  I won’t even ask for credit. 


P.S.  My ardent followers (all seven of them) have, for a long time, expressed their overwhelming desire (!) for me to get on Twitter.  Well, ask and you shall receive.  Join me on Twitter on Thursday, October 22nd, at 10 a.m. PT when I will talk about the future of batteries for EVs & grid storage.  I think this would be described as a Twitter chat.  The hashtag is #BattChat