Wednesday, February 6, 2013

Are you charged up? Because we are ready to go!

Succeeding in the battery space is hard.  One needs a technology that has some advantage over existing technologies; the advantage has to be large enough that one can compete with existing players, especially ones that are in Asia.  The technology has to be manufacturable at a low cost so that one can compete without requiring a large cost premium.  And one has to to maintain the advantage as competitors try to catch up.  

But its not just about the technology.  If you don't have a technology that satisfies a market demand, then its equally likely that the company will not succeed.  

And in some markets your efforts may be stymied by the regulatory policies that may prevent the battery being developed from being used. 

What this means is that to succeed, you need to have the right battery technology, the right manufacturing methods, go after the right markets, and use regulations to your advantage.  Tall order for any one person to do by themselves!

So how does one learn about all of these things?

Say Hello to CalCharge: The consortium that Berkeley Lab and CalCEF have formed to accelerate innovation by forming a regional innovation cluster. Read about CalCharge here.  

CalCharge has teamed up with San Jose State to start what we are calling "Battery University"- a professional educational program that will address the technology, market, and policy challenges. You can learn all about this and get the latest news about batteries in California at a kickoff event scheduled for next Tuesday Feb 12th at 6 PM at the Network Meeting Center in Santa Clara.  

Former Senator Bingaman, who was the Chair of the Senate Energy and Resources Committee, will provide us his views on storage, the importance of regional innovation clusters, and the role the federal goverment can play. We also have a roster of great speakers from SJSU, Applied Ventures, and Proctor and Gamble.  

More importantly, you may even have a chance to see me speak. 

Learn all about it here

It is the start of something great.  Its a good way to learn about storage, and to network.  We will even have a setup to watch the State of the Union at 6 PM before we launch into the program for the day.  

So come join us to get charged up.  

Venkat

 



Saturday, December 15, 2012

And here are the lucky winners

I have a new found respect for movie actors (not stage actors, mind you).  Being in front of a camera makes you self conscious in a way being in front of an audience does not.  I can see why Arnold stuck to one liners! 

Anyhooo... last week, I asked via a video blog to send in your questions on all things batteries.  The response was infinitely better than I expected (ponder that sentence for a second and you will see two ways to interpret that). I answered a few of the questions.  

The questions were all very interesting ranging from how we can make a battery that is five time better and five times cheaper to how one can become a battery scientist (start a blog?). 

The clip with the answers is below.  I assume there will be followups.  You can post them in the comments and I will answer them.  It may be during the Holiday break, but I will answer them.  






Venkat

Saturday, December 8, 2012

Ask and you shall receive... maybe

This is a bit embarrassing.  TWiB is getting updated twice in a week!  I shall try to average things out after this by not posting for a couple of years!  Just kidding folks.  Changes are on the way.  2013 will be a bonanza for all seven of you.

But, let us get back to the task at hand.  My Lab has decided that sitting on planes all day is not really "doing work".  So I have been asked to get some tangible things done for a change.  But first, they would like me to prove that I actually know something about batteries!

So, please watch the video below and ask your questions.  I will be answering a few of them next week in another video blog.  

So ask away.  

Venkat



Monday, December 3, 2012

What’s all this hubbub about a Hub?


All seven of my fans are aware that I have not been blogging much over the last year and a half.  Part of the reason is that I had, for all practical purposes, relocated to Chicago since the summer of 2011.  I (and many others) spent that one year working on a proposal with Argonne National Lab, which culminated in an announcement that our team had won.  The proposal was for an energy storage (i.e. battery) hub.  This is great news all around.  I have gotten a lot of questions on this, so I decided to write this post to get some information out. 

First, the announcement from DOE is here.

Now comes the FAQ.

There is already so much battery research going on.   What’s the big deal?

Ahh… the million dollar (or the $120M) question!  There is a lot of wonderful battery research already happening (and I’m part of a couple).  But we have very big challenges.  We need batteries that have 5 times the energy density of today’s batteries and have to be 1/5 the cost.  Right now, battery energy densities evolve at just 5% a year!  So the Hub is doing three things that are very different from existing battery efforts:

1.  It puts scientists and engineers, materials researchers and theorists, industry and academia all under “one (virtual) roof.”  This idea is not new (Bell Labs comes to mind and this was essentially Energy Secretary Steve Chu’s vision when he started the Hub proposal process), but it is new to batteries.  And doing this in a deliberate fashion instead of hoping for self-assembly is very important.

2.  It embarks on a new process of innovation.  This is a bit too detailed so I will not elaborate more, but let me just say that what we are planning to do in the Hub is very different from what has been tried in the past.  We hope that this new way of looking at batteries will help us find completely new materials that store energy, beyond what we can dream of today. I’m really excited about this.

3.  It brings together researchers who really understand batteries and puts them in close connection with folks who are experts in, say, materials, but who might be new to batteries.  I would posit that innovation occurs when this connection is made and new thought is brought to an old field.  This, too, is something that can be a game changer. 

But 5 times increase at 1/5 the cost in 5 years?  What are you smoking?

Folks who read my blog posts will know that while I may have one or two flaws (although nothing comes to mind at this moment), naivety isn’t one of them!  We fully appreciate the difficulty of the goals.  But this is what the world needs.  If we want electric cars (EV) everywhere and a way to store energy from a solar panel on our roofs, we need to do this.  That is the bottom line.  Let us not be naive in what the world needs.

So we are dreaming big.  But we are not violating any laws (well… maybe Moore’s Law for batteries, but not any laws that actually matter, like, Faraday’s Law).  These are theoretically possible.  It is however, hard. Very hard.  Hence, the need for a Hub.

And talking about smoking, it’s not all about energy and cost.  Safety will be an important aspect of our studies.  So will battery life and efficiency. 

I don’t care about EVs.  However, I do want my iPhone to last a bit longer. Can we get a Hub for that?

Anyone who really understands batteries will tell you that a good battery is a good battery.  So, on the way to making a better EV battery, we will probably make a better iPhone battery. Actually the path to an EV goes through the consumer electronics world. 
Our focus, however, will be on better EV batteries, and better grid storage batteries.  Think long discharge times.
Think long life.
Think cheap. 

So, what is this, a new kind of Li-ion battery?  Aren’t those like 20 years old or something?

First off, today’s Li-ion battery is not the same as your father’s Li-ion battery.  Far from it.  Having said that, we are looking at things that will go beyond Li-ion.  Actually, if everything works well, we may have a new kind of battery, which may have no lithium in it. 

What is Berkeley Lab’s role in this? 

Berkeley started working with Argonne on this proposal three years ago.  Our efforts intensified a year and a half ago.  Argonne and Berkeley Lab are the two big labs in battery research in this country focusing on vehicle batteries.  Our team was rounded out by labs and universities that brought grid storage experience and other specific expertise.  And we tied in with companies to ensure that we can deliver something scalable and manufacturable. 

Berkeley Lab has a very well known battery program already that understands everything you need to know about a battery and can translate fundamental knowledge to lab-scale prototypes, a very well known materials sciences program that can make any material at any scale, computing facilities that can predict things that have never been possible before, and a bunch of user facilities that can help see things at scales that are unprecedented.  We will be using all this in the Hub. 

You can read about the Battery Lab role here

Material Science, computation!!  Why are we spending tax dollars on these ivory tower projects? Can we get a job’s Hub instead?

Funny you should ask.  One of the underlying principles of Hubs is to get stuff out the door.  It is not science for the sake of science, but science with an impact.  This ethos is built into the Hub.  There will be hiring of not just postdocs and students, but training of the next generation of scientists and engineers.  There will be technology transfer to our industry partners in the Hub and to other companies that we have ties with. And, we will be moving things to the marketplace via startup companies.  We are trying to build a complete innovation network.  I wrote an op-ed recently in the San Jose Mercury News on how these networks will be critical in creating jobs.  You can read that here.

So, is Silicon Valley going to move to Chicago? 
Please.  Get real.  Chicago is a plain. Not a valley (I think).  So, Storage Plain, maybe?

But seriously, Chicago is trying to get a Silicon Valley-type idea in place focused on batteries.  So are Michigan and Boston (although they have a head start). 
Probably the biggest such collection of companies in batteries is located right here in California.  A few months ago, Berkeley Lab teamed up with CalCEF to start CalCharge, an innovation consortium focused on batteries.   You can read about it here.   

I’m really excited about CalCharge, too.  In addition to all the battery research in California, the Hub will provide us with more tools to innovate.  We are now very well poised to move technology to market in a rapid fashion. 

So, No. Silicon Valley will not be moving to Chicago. Instead, we will have four centers where innovation ecosystems will thrive.  And they will all help create jobs. 

Now that you are not travelling, can we expect more blog posts? Or, at least a change in title to, “This Year in Batteries”?

Maybe.  But I’m beginning to realize that I have missed a full year of TV watching.  Numerous episodes of Sherlock, Downton Abbey, and This Old House beckon.
But let’s not start jumping to changing titles just yet.  Lord knows how many more months it will take to get back my seven readers to the new site.  TWiB will be going through a change (based on a suggestion by a colleague).  Stay tuned.

Venkat 

Sunday, May 6, 2012

Are you tired of Li-ion yet? Then it’s time to go beyond it.


Those of you who are faithful followers of this blog (all 7 of you) should know that I come from the school of thought that you always need a better battery.  I even have a law for this, which I call the zeroth law of batteries and it states:

The performance of any battery will fall (just) short of our expectations irrespective of the complexity of the device it is powering.  

This is true for our cell phones and Roomba’s.  And true for electric cars and plug-in cars.

That is, unless you have low expectations. 

The world has seen some dramatic changes in battery technology over the last 20 years, ever since the Li-ion battery became commercial.  For one, the smartphone revolution would not have occurred if not for the batteries.  A lot of improvements are still possible with lithium-ion, and we project that battery energy densities will double when we succeed in controlling more energetic anode and cathode materials. 

But what happens after that?  At the pace at which my smartphone is evolving, with Retina Display screens, 4G networks, and movies playing off of the air, it’s hard to see a doubling in energy being enough. 

Question then is: What is after Li-ion batteries?  And is there something out there?

The answer is: Yes.  But getting there is not going to be easy. 

I wrote about this in two blog posts titled “A brief history of batteries- Part 1” and “Part 2”.  These two posts describe possible battery chemistries of the future and make the point that to succeed we really need to understand the past.  And it is written in the style of the movie “Pulp Fiction”. Can any battery textbook beat that?

I would suggest that you read this blog post first. 

Once you do that, you will want to know: So what is the progress in these chemistries in the two years that have elapsed since the blog post? 

You will get an answer to this question if you show up at the Claremont Hotel in Berkeley CA between June 5-7, 2012 (a month from today)*.  This will be the venue of the 5th in a series of symposia titled “Beyond Li-ion”.  In a 2 ½ day period various researchers, who are at the forefront of this field, will tell you what the latest trends are. 

It is an impressive speaker list, which you can see here

As a bonus, you will get to come to Berkeley Lab to see our Lab facilities.  More importantly, you may (I should emphasize the fact that this is a real possibility) actually get to shake my hand! 

To attend you will need to register, which you can do here.   

Hope to see you all (and I mean all 7 of you) there. 

Venkat

p.s.  Please don’t ask me to waive your registration fee.  Being a co-organizer means that I write blog posts to promote the meeting. It does not mean that I can come up with the cash to pay for your meals.




* The previous version wrongly gave the date of the conference as July.  It is June 5-7, 2012  

Sunday, April 29, 2012

TWiB is back (hopefully with actual content next time)


Over the last year numerous (!!) folks have asked me why I have not written a blog post.  Even at the best of times, the title “this week in batteries” was a wee bit optimistic.  A better title would have been “this month in batteries”, but TMiB is not a pronounceable acronym.  But the last year has been particularly slow going at TWiB. 

Turns out that I have been extremely busy this last year.  We had decided to remove cable television and move to using a Roku box with Netflix.  You will be amazed at how long it takes to get through all the seasons of Lost, CSI, 24, Community, and the rest Netflix’s content (answer: a year!). 

Anyway, all good times come to an end and I’m pretty close to being stuck with watching things real time. 

While I’ve been glued to the box, many things have changed in the battery world.  President Obama decided he wanted EVs Everywhere, my home state of CA decided that they wanted 15% EV and PHEVs by 2025, and Governor Brown has decided he wants charging stations everywhere.

Meanwhile, battery energy densities, after evolving at 5% a year, doubled this year. 

Simultaneous, one battery company declared (Chapter 11) bankruptcy, another company is having financial difficulties, cars are catching fire, and batteries are catching fire. 

To top it all funding to cleantech seems to be getting harder. 

Is there a mismatch between what the government wants to see and what batteries can deliver?

And are we about to hear a “pop” (of a bubble bursting)? 

It seems like someone needs to be discussing these issues.  And I can't think of any other forum but TWiB to do it.    

Unfortunately, I beginning to realize that at this stage, I’m more qualified to talk about why season 2 of Community seemed worse than Season 1, than I’m about the status of battery technology.  So, over the next few weeks, I’m going to brush up on my knowledge and hope to be back to writing regularly. 

So stay tuned folks… I’ll be back. 

Venkat


Monday, March 28, 2011

To be, or not to be (green), that is the question


The title above was going to be my next blog post for GigaOm.

But, they thought a better title was “How Plug-In Hybrid Cars Could Be Game Changers”.

I still think my title is clever (and I’m sure Shakespeare would approve), but on a site like GigaOm, it does not say anything about the content of the blog post.   I’ve never worried about things like that, but it’s the price you pay for playing in the Major Leagues :-) 

Anyway, I’m beginning to think about the Chevy Volt.  Not sure I agree with the title, but I’m seriously thinking about it.    

Read all about it here


Venkat 

Saturday, March 19, 2011

One year and a change in TWiB


Over the past couple of weeks, I have been in conversation with the folks at GigaOm network to be a guest writer for their cleantech blog called Earth2Tech

After consulting with my employer (Lawrence Berkeley Lab), I have signed an agreement with GigaOm to be a guest writer.

What this means is that when I write a blog I will send it to them.  If they think the post meets their needs, then it will appear on their site.  This page will be updated with a small abstract of that post and a link to their site. 

If GigaOm decides to not use that post, then the post will appear, in its entirety, on this page. 

This Week in Batteries started just over a year ago on Feb 9, 2010.  Over the last year, I have made ~30 posts on subjects ranging from the costs of PHEVs, the way to make a battery last longer, the batteries in your Roomba, all the way to how to calculate the energy density of a battery.

Making a blog post has become a hobby for me (probably the first true hobby I have ever had.  Collecting stamps just did not cut it!).  But like all hobbies it tends to be a fairly low item on the priority list.  Regular readers will have noticed the long hiatus’ I have taken when work has demanded more of my hours. 

When I wake up on a Sunday and feel like writing, I spend the morning making a post.  If I have something else to do, then I don’t make a post.   On average, I probably spend 2 hours on a blog post. 

The return on the 2 h investment has been very gratifying.  I average 5000 hits a month (please don’t ask how many of those are self hits!) with a peak at 10,000.

I have also become convinced that if I really worked at it, I could make this blog popular.  But this requires a lot more of my time.  And even if I did spend the time, I’m not sure how much more popular I can make it. 

On the other hand, GigaOm gets 4 million hits a month.  And some of their blog posts gets picked up by the New York Times, CNN, Business Week, and The Street. 

Being able to get my posts onto GigaOm increases the visibility of this blog significantly, so the relationship is a no brainer. 

The first post is now up on their site.  Its called the “The Three Laws of Batteries (and a Bonus Zeroth Law)”.  Check it out.   They even added some nice pictures to accompany the words. 


For the regular readers of this blog, this only means that you will need to, occasionally, click on one more link before you can read my post.

So wish me luck.

Venkat 

Monday, February 7, 2011

I'll be back... in 8 hours

Some of my readers have wondered why I have been off the blogosphere in the last few months. The reason is that we brought a house and the move from the apartment to our new place has been a bit of a time sink.

First we went through the four stages of home buying:

Stage 1: What the &%#@ do you mean they accepted our bid? I thought you said we were lowballing?

Stage 2: When you use words like "downpayment", does this involve us giving you a check?

Stage 3: I assume roof's are like batteries? Meaning, when you say it is at the end of its life, there is still 80% left, right?

Stage 4: Keep repeating after me: "Owning is better than renting" and, please, stop asking "why?"!

Then we realized that owning a house also meant owning things like leaf blowers and lawn mowers! So, when I saw that there was a battery-powered lawn mower, I jumped at the chance to push my favorite technology forward.

I was looking forward to using my expertise in batteries to maintain and extend the life of my lawn mower for many years to come.

I was not particularly looking forward to mowing the lawn, but owning a battery-powered mower seemed to make up for that.

Until I realized that the top-rated battery-powered mower uses lead-acid batteries.

Lead-acid!!! really! How old school can one really get.

My first thought: Start a battery company to make Li-ion batteries for lawn mowers.

Then I started thinking about this some more. There must be a catch here. So I started digging into what it was.

Let us do some math: The battery for this lawn mower cost ~$270/kWh. That is one expensive lead-acid battery. Presumably, it is a deep-discharge battery, and so it is better made than a car battery.

And there is probably a significant markup.

Did I mention that the mower was on sale for $300! More like a mark-way-way-up.

Considering a typical Northern California growing cycle, this mower will probably be used ~50 times a year (once a week). These deep-discharge batteries can probably go a few hundred cycles. So I'm thinking 4-5 years easy.

But the bigger problem is going to be the calendar life. Sulfation can kill these cells.

Having said that, the battery is probably going to be at the top-of-charge pretty much through its life (think about it: Mown for 1 hour. Keep it plugged in all week). And remember our rule for lead-acid batteries: Keep them charged. So I think we can expect to get ~3 years from these cells.

Lets do some math for a Li-ion battery. I bought one a few weeks ago. This battery will probably last me 3 years and get me ~300 cycles or so. So it has similar specs to the lead-acid battery.

The Li-ion battery, on the other hand, cost me a whooping $2300/kWh!! No... really. This is what it cost me.

Now... knowing Apple, a new word has to be coined for their level of markup. But still this is one expensive battery.

At this price, a Li-ion lawn-mower-battery would have cost me $800!

All you MBA-types are probably cringing because you all know that cost and price are very different from each other and that the price is dictated by what the market is willing to pay (my wife is an MBA and she gave me this spiel).

Granted. So let us do a cost-differential comparison. This comes out to be ~$50/kWh more expensive for a Li-ion cell. Using this, the cost of a Li-ion battery for this mower would be higher than the lead-acid battery by... the price of lunch!

Not at Chez Panisse. But at the LBNL cafeteria (same quality, but at a much lower price?)

So why not use a Li-ion instead. After all it is almost 5x the energy density.

The mower that I have been talking about in this blog is a push mower. So the battery does not need to drag itself. All it has to do is turn the cutting blade. And space is not a big constraint. The mower's size is dictated by the size of the blade anyway.

So why bother using a new type of battery when you don't really see much of a benefit?

Frankly, although I have not looked at the life-cycle, I'll take a bet that it is probably better for the environment to use a lead-acid battery considering how much of this lead is recycled. In comparison, all you recycle in a Li-ion is the high-value metals in the cathode. The rest, literally, goes down the drain.

Maybe the math will change for a self-propelled mower. Or if the weight of the mower is an issue. But I don't see any reason to jump to using a Li-ion battery for the mower I was looking at. This business plan does not appear to have much legs.

So what did I do? I got the corded version of this mower. It cost me $100 less.

I guess the price that I'm willing to pay to push my favorite technology forward is less than $100!

In my guilt I decided to do my part for the technology by buying a Roomba.

I'm not sure if you guys know about this amazing robotic vacuum. It is pretty interesting to watch. It has sensors that make it slow down when it approaches objects, detect dirt, and prevent it from falling off of stairs.

It is not particularly good at vacuuming. But it feels like it is cleaning the floors and isn't that what's important!

But here is the kicker. The one I have has a Ni-MH battery.

I suppose I should be thankful it is not a lead-acid, but Ni-MH? COME ON!

The last time I checked, the cost of Li-ion and Ni-MH batteries were pretty comparable. And the energy density of Li-ion is 2-3x greater. And remember that in this machine (unlike the mower) the vacuum has to drag its battery along. And space is a big deal. The smaller the footprint, the smaller the space it can vacuum.

So why use a 20th century battery for a 21st century machine? Strange.

A web search revealed that Li-ion Roomba's have apparently died prematurely. If this is the case, then iRobot (the company that makes the Roomba) needs to change battery suppliers.

The vacuum I got goes through 2 rooms and then runs out of juice. It could have finished my house in one charge if it had a Li-ion of the same size. Or you could have a better vacuum on it so that it actually picks up dirt instead of moving it around and still only vacuum 2 rooms. You get the point.

When I first saw this machine, I thought that all the things on Terminator (the movie) were coming true. Jokes apart, it really is a pretty decent robotic cleaner which does indeed find its way around. You can, pretty much, set it and forget it.

But then I realized that we had nothing to worry from the machines as long as battery technology evolves the way it has been in the past.

When Arnold Schwarzenegger's character said "I'll be back" on T2, he (it) actually meant "I'm running out of battery and I need to go find an outlet and charge for 8 h. I will then come back to look for you for the 1/2 hour my battery lasts. Wish me luck".

So much for the machines taking over.

If you constantly complain about how batteries are not evolving fast, did you ever consider for the second that maybe we are out to save the world in our own way?

Venkat

Monday, January 31, 2011

Did I say “Pull the Plug”? Meant to say “DO NOT pull the plug”

This could be a mea culpa post. It is rare that I’m wrong; it is even rarer that I admit it! So listen up folks.


In the early days of this blog, one of my dedicated (?) readers had asked me about the urban myth about not keeping the laptop plugged in to extend the life of the battery. In response, I had written a post titled “Pull the plug, your battery will thank you”. This post is the single most popular post on this blog. Almost a year after the post was made, it still gets the most hits.


The logic behind doing this is very sound. As you can read from that post, it has to do with side reactions that occur in the battery at the top of charge. Letting the battery discharge a bit is good for life because the rate of these side reactions decreases with decrease in the voltage. Suffice to say that I recommended you wait for the battery to charge and then you pull the plug and let it self discharge. This way you can extend its life.


I follow this rule pretty diligently. And I thought it had worked well for me. I have one laptop that is 2 years old, has had 297 cycles and has lost 4% of its initial capacity. Not bad. This is my workhorse. I use it every day and although I pull the plug diligently, my usage is such that I keep it pretty close to fully charged. So over the last 2 years, it has spent its time at close to, say, 4 V.


I have another laptop which is 3 years old. It is my personal laptop which we (my wife and I) use typically only over the weekend. We pull the plug diligently, but then the computer sleeps all week; self discharges; and by the end of the week is pretty much discharged. This battery, as of last week, had not lost any appreciable capacity even after 350 cycles.


These two data points tell you something about batteries. The cell with more cycles and with more time is cycling better! No magic. Just a simple fact that the battery was sitting at a lower state of charge and so the side reactions were not as worse. Ergo, better life.


Did I mention that both these are Macs? I have a third laptop given to me by a startup where I spend some of my time. This is a PC assembled by a company whose name starts with a D and ends with an L and has 4 letters to it. That computer is on its 4th battery in 2.5 years. After I lost my first battery I spent significant time trying to understand why my rules were not working and trying to tweak the rules. Soon, I came to the conclusion that with some batteries there really is no point trying to find ways to extend life. They are beyond help.


Actually, these rules have been helping this battery also. But different battery companies make batteries with different quality (achieving tightly-bound quality metrics has been a challenge in the manufacturing of batteries). So when you start with a battery with bad quality, there is only so much you can do.


But let us get back to my Mac.


Well... last weekend, my 3 year old Mac with no capacity fade suddenly appeared to have a dead battery. Not a battery with some loss in capacity; or one with 20% loss in capacity (which is considered dead). It was just plain dead. No charge; pull the plug and it would shutdown. It was on life support, literally!


The only way this battery would have a second life was if it were a Hindu and had not attained enlightenment and so was eligible (I suppose doomed is a better word) to be reborn. Somehow it seemed like even with the 1000 (or is it 10,000) Hindu gods there was no way to get this battery back up.


My first reaction was one of disbelief. There was no way a battery can go from no fade to completely dead in a matter of 1 week of self discharge. It had to be a software glitch that was not allowing the battery to be used.


Two hours, a bit of heartburn, and a detailed scouring of the world wide web later, I found various tricks to reset the battery management software and a software to measure the voltage of the battery and came to the conclusion that it was indeed dead. The (average) individual cell potential appeared to be close to 1.5 V! The typical cutoff potential of these cells is around 2.5 V.


So I pulled the plug and my battery died!!


A call to Apple confirmed that I was out of warranty and was told to go to the Apple store for a “detailed diagnostics”.


So I dragged myself to see the “genius” at the store (I’m not being condescending here; they really call the tech support guys genius’. Apparently if Einstein were alive today he would be working at the Palo Alto Apple store!).


Albert plugged a USB stick into my laptop; my screen turned into a series of numbers. Albert then turned and says that my battery is dead. Clearly he was on his way to writing a paper on the unified field theory.


I apologetically told him something like “I understand a bit about batteries and I don’t expect them to fail like this” and he said “I would not expect them to do that early on, but after 3 years I fully expect this”. Not “its possible”, but “fully expect”!!!


I debated giving up versus trying to argue on the finer points of battery chemistry but it seemed like a lost cause. I’ve been very reluctant using my celebrity status as the author of TWiB, and I have to say that it is intimidating arguing with a “genius”!


So I shelled out $130 for a new battery; thanked the guy for his help; and left.


I drove back re-examining my whole life and everything I know. I always thought there was some merit to the George Costanza (of Seinfeld fame) principle of doing the opposite of what our instincts tell us. Maybe I had it all wrong. Maybe you should not be pulling the plug. Maybe my jingle on battery rules needed to be rewritten.


A couple of days later my confidence started to return. I decided to do what anyone looking for credible information does: perform a google search to see if plugging in your laptop battery is bad. I came across my original blog post on this topic.  I sounded so convincing in the post that I started to get re-convinced that I was right about my rules.


So what is going on? How can a battery die when it is self discharging on sleep?


Here is my take.


All you PC folks are familiar with the hibernation mode that you can either force your computer to enter, or set it such that the power management utility moves the computer to hibernation after a while of being at sleep.


In sleep the computer stops many of the processes from running and thereby decreases the processing needs and hence drains the battery slowly. In hibernation, the computer (presumably) stops pretty much everything; stores the state in memory; and basically shuts down. This means there is very little drain on the battery.


In a Mac there is a sleep option, but there is no hibernation option. However, if you are in sleep and if your battery drains down to some small state of charge (say 5%), then it automatically moves into a “hibernation” mode; freezes the state and stops all the processes.


One thing we had noticed in the dead Mac (before it died) was that when we opened it over the weekend it was pretty much in hibernation with little juice left in the battery.


Ideally hibernation in a low state of charge is a good thing. Remember the rule “don't charge them too high”? Higher the voltage of the battery, worse will be its capacity fade. So storing it at a low state of charge (or low voltage) is actually good for the battery.


Did I mention that keeping the voltage way too low (i.e., over-discharging) is a bad thing?


This is because many cathode materials can get irreversibly damaged on over-discharge. More importantly, if an anode is over-discharged you can start dissolving the current collector (copper).


When you discharge the battery and it reaches its end of discharge voltage, depending on the battery chemistry (i.e., the anode and cathode that it uses) and on the design of the cell, the battery is limited by either the anode not having any lithium left, or the cathode not being able to accept any more lithium.


As you cycle this battery there are side reactions in both the electrodes. The extent of these side reactions depends on the design of the cell, the chemistry of the electrodes, the composition of the electrolyte, the level of impurities in the manufacturing, the way the battery is formed etc.


In other words, the side reactions are pretty complicated.


However, what we need to understand is that these side reactions can actually change the way the electrode reaches the end of discharge. They can even change which electrode limits the end of discharge.


So here is my take on what happened to the Mac battery.


The battery management system had a methodology of estimating the state of the battery and deciding if its needs to jump from sleep (the usual mode) to hibernation. This estimation was probably pretty accurate at the beginning of the life of the battery.


But years pass (3 in my case); the side reactions chug along; and they start changing the shape of the voltage curves, especially at the end of the discharge. Slowly, but surely, the management system was making errors in its estimation on the remaining charge.


The battery was not fading appreciably. Instead it was becoming harder to predict the time it would take to go from, say, 5% SOC to being fully-discharged.


I think that as my battery kept fading, the transition from sleep to hibernation was not getting triggered correctly, the battery over-discharged.


This is why when I checked the battery voltage it was sitting at 1.5 V.


I have a sneaking suspicion that my battery may actually come back to life if charged but that the power management software is not allowing any charge to reach the battery because the battery voltage is so low. I should have asked for my old,dead battery to try to resuscitate it myself!


If this sounds like an easy explanation considering how complicated all this is, its because it is the only plausible explanation I can come up with. If Steve Jobs would like to disagree, I’m listening.


So I still believe that if you “pull the plug, your battery will thank you”. I am glad I don’t have to go back and change 7 of my posts and apologize to my regular readers (all 7 of them!)


So what can one do about all this? Download the desktop hibernation widget at http://deepsleep.free.fr/ This gives you a way to move your Mac directly into hibernation instead of to sleep. This is probably a good thing anyway to conserve battery on long trips etc.


Or you could buy one of the new Macbook air computers which comes standard with hibernation.


In the meantime, my rule stands: Pull the plug, and your battery WILL thank you.


When Albert at the Apple store told me he “fully expected” my battery to behave this way, maybe, just maybe, he actually knew all this. After all, he is a “genius”.


Venkat