Electric vehicles

17May 2018

I googled the question “ should I charge my phone to 100”. Google returned 467 million results. From folks offering opinions on “how to properly charge” to others calling on “science”, there seems no obvious consensus in the media. Yet,  unlike views on more socially charged topics, this question ought to be a lot simpler and ought to have a clear cut answer. Let’s explore.

I start with an easy experiment. Take two batteries. Charge one of them continuously to 100% and discharge it back to zero. Repeat. Take the second battery and charge it only to 90%. Discharge it. Repeat. Now compare the two batteries.  Are there differences? the answer is yes, there is difference. The battery that was charged to 100% will age considerably faster. 

What do I mean by aging? The technical term is “cycle life.” In practice, it means that the battery charged to 100% will lose its ability to store electric charge faster than the other battery. The difference between the two batteries can vary between 100 and 300 charge cycles.

So is that good? Well, it depends on what your use is. The definition of “good” is relative.

For a smartphone, my answer is “I really don’t care.” 

For an electric vehicle, my answer is “yes, it is better, but may be only marginally.”

For energy storage batteries used by electric utilities, my answer is “yes, absolutely.”

Now, let’s dive into the details.

A smartphone battery usually lives about 500 to 800 cycles. By cycles, I mean the number of times you will be able to charge it (to 100%) and discharge it before it becomes old and useless. Some smartphone manufacturers do better than others. Apple’s and Samsung’s batteries tend to be closer to 500 cycles. Others like LG, Sony and Huawei tend to be closer to 800 cycles. 

Let’s convert cycles to real-life years. Most smartphones are charged once a day. So 800 cycles is about 2 years of use before your battery becomes old. That corresponds well with the average time for consumers to upgrade. But wait, you might say you plan to keep your smartphone for longer than 2 years. What should you do?

Naturally, one option is to spend $30 to $50 once your battery is depleted and get your phone serviced after 2 years. The other option is to charge your phone to only 80% or 90% instead of 100%. That exercise will probably get you an extra year of usage.

But that is not the only way to get more longevity. You probably don’t know that if you use a small AC adapter instead of a bigger one, you will probably get the same benefit. For this method, look for an AC adapter that is rated 5 Watts, or use the USB port in your PC to charge you handset. And that applies to iPhones or Android phones. What do you give up? You are giving up fast charging. If you charge your handset overnight, then you really don’t care.

A self-serving plug for Qnovo: Smartphones with intelligent charging algorithms will take care of longevity issues for you so you really don’t have to think about this question and its answer. 

Now, let’s talk about electric vehicles. Should you top off the battery in your electric vehicle (EV)? First, it is important to know that EV manufacturers (from GM and Tesla to Nissan and VW) already limit the charging of the car battery to somewhere near 80%. The 100% that you read in your dashboard is actually 80% of the what the battery is rated for. That figure usually is sufficient to meet the warranty terms of the vehicle, often 100,000 miles or 10 years.

If you are leasing your car, then you really don’t care. Your lease will expire long before any meaningful battery aging sets in. But if you purchased your EV and plan to keep for a long time, then you may have an incentive to not top off your battery.

But wait, that is also not the only way to get more longevity. Every time you use a supercharger or DC fast-charging, you are causing serious damage to the battery. So instead, try to avoid using superchargers. This is particularly acute for the Panasonic batteries used in some of the Tesla models.

Lastly, I will add a few final words about electric utilities and batteries they use. These are complex systems that are slated to operate for at least 20 years! They are also very expensive assets that cost millions of dollars. So longevity is a serious matter. Naturally, users have no say in how these batteries get charged. Utilities and battery manufacturers do watch over these batteries so that they can last for a long time.

29Nov 2017

Congratulations, you just purchased a new Tesla model S electric vehicle (EV). You also committed an extra $2,000 to install a level-2 charger on a wall in your spacious garage. A level-2 charger will deliver 6 kW of power at 240 V to charge your big car battery overnight. Better yet, you are even considering investing an additional $20,000 to install solar panels on your roof and live a life with zero carbon. You might be cringing by now and thinking: “Wow, this is for the rich, not me.

So let’s consider instead a more socially responsible scenario. You leased a much more affordable Chevy Bolt that promises to give you 200+ miles of electric driving. You don’t have a garage. Perhaps you live in a large city so your car may be parked on the street. You are scratching your head: “How will I charge my car battery?” You might be lucky to charge your car during the day at work instead of overnight at home. But what about the weekends? No quick and easy answer.

As the adoption of electric vehicles becomes more widespread especially in congested urban geographies, questions about the charging infrastructure become prominent. Tesla leads in the deployment of their Supercharger network with over 1,000 charging stations installed worldwide, especially near major transportation corridors and highways. But the Tesla fast charging network is not compatible with other electric vehicles. Imagine that you can refuel your present vehicle at only one brand of gas stations, say at Shell only but not Exxon. No practical!

The buildup over the coming decade of a charging infrastructure that is publicly available to all electric vehicles is a must if EVs are to become a real alternative to vehicles powered by gasoline (or diesel). A fundamental requirement for charging is the availability of fast charging, more specifically, charging that can provide at least half-a-tank (or ¾ of a tank) in about 10 minutes.

Let’s do some simple math. An electric vehicle with a 200-mile range equates to a battery size of approximately 60 kWh. Half-a-tank is 30 kWh (or 100 miles). Charging 30 kWh in 10 minutes equals to 180 kW (or 3C effective rate). By the time we factor inefficiencies, the charging station needs to deliver a minimum of 200 kW. To put that in perspective, that is the amount of power used by an entire residential block! These chargers are big, expensive and hence have to be shared among dozens if not hundreds of vehicles.

But the infrastructure for fast charging is only half the problem. The elephant in the room remains: Can the battery itself charge at such a fast rate without being damaged?

The data suggest otherwise for the time being, unless we add a lot more intelligence to how we charge the battery.

The following chart shows the results of charging a battery at a slow rate compared to fast charging the same battery 30% of the time (or about once every three days) and 50% of the time (every other day).

The green curve shows how the battery retains its charge with slow charging. After 700 charge cycles (or about 130,000 miles of driving), it still retains 90% of its original charge. In other words, you can still drive 180 miles in what used to be a driving range of 200 miles. That is good!

The blue curve shows what happens if you charge 30% of the time. The capacity retention drops to 80% after 600 charge cycles. That is a rapid degradation. After 100,000 miles, your driving range is now 160 miles. It might be acceptable to some EV buyers but just barely. The resale value of your car has depreciated substantially below the average value.

The red curve spells major trouble. If you fast charge your electric vehicle every other day, your battery capacity drops to 75% of its original charge after only 300 cycles. That means that your driving range drops from 200 miles to 150 miles after about 50,000 miles of driving. What this graph does not show is that this battery is failing rapidly and has now become a serious safety hazard because of the presence of lithium metal plating. This is a serious problem!

So, if you own an electric vehicle such as a Tesla, and you are tempted to use the Supercharger network frequently, consider an alternative charging solution !!

31Mar 2017

We, that’s all of us on this planet, buy every year 1.6 billion smartphones. It works out to one new smartphone every year for every four living human beings on this planet. Cumulatively, we own and use 4 billion smartphones around the world. Every region of the world, rich or poor, is buying smartphones. Many developing nations in the Middle East, Africa, and Asia are growing their smartphone subscriptions at a fast rate. Ericsson reports that by 2021, there will be 6.3 billion smartphone subscriptions, that’s nearly every man, woman and child around the world. Impressive!

Of course, each and every one of these smartphones has a battery in it. Your first reaction is: “that’s a lot of batteries.” Yes, that is true. Sadly, many of these batteries go to landfills after they are exhausted. The easiest way to gauge the size of the market for batteries is to calculate the entire energy supplied by all of them. Of course, that is a large number. It is measured in billions of watt-hours, abbreviated as GWh. As a reference mark, the battery in a top of the line Tesla S is 100 kWh. One GWh = 1 million kWh = 10,000 Tesla S.

 

Screen Shot 2017-03-31 at 9.48.15 AM

 

In 2016, the battery factories around the world manufactured about 50 GWh worth of batteries for consumer devices. That drives an industry and a market worth in excess of $10 billions annually. Forecasts indicate that the consumer market will use about 65 to 70 GWh worth of batteries in 2020. Our appetite for more batteries is insatiable and the numbers show it.

Now let’s look at batteries in electrified vehicles, including both hybrid plug-in cars and pure electric cars (xEVs). This is a relatively new market. The Tesla S first came in 2012. The Nissan Leaf came a little earlier in 2011. Many states in the US or countries around the world haven’t yet experienced or experimented with such vehicles. In 2016, all of these vehicles accounted for a mere 0.9% of all car sales. In total, they amounted to less than 1 m vehicles in 2016.

 

GWh

 

However, in battery lingo, these cars accounted for an increasingly large number of GWh. The year 2016 was the first year that the battery capacity used in xEVs equalled that of all consumer devices, about 50 GWh. By 2020, xEVs will account for ⅔ of all battery production in the world. No wonder Elon Musk and the major car makers pay a lot of attention to their supply chain, including building these Gigafactories.

 

23Aug 2016

Tesla Motors announced today upgraded versions of the Model S and X boasting 100 kWh battery packs, up from 90 kWh used in their earlier top-of-the-line electric vehicles. One hundred kilowatt-hours sounds like a lot, and it is, but I bet that many readers don’t have an intuitive sense of this amount of energy. This is what this post is for.

First, a kilowatt-hour is a unit of energy, not power, and is most commonly used in electricity. To put it in perspective, an average home in California consumes about 20 kWh of electrical energy per day, so this 100-kWh fully-charged Tesla battery would cover this home’s needs for about 5 days.  Now that’s great if you like to go off-grid.

A Nissan Leaf has a battery with a capacity of 30 kWh and has a driving range of approximately 107 miles (172 km). If the Nissan Leaf were to have its battery upgraded to 100 kWh, then its range would increase to 350 miles, or about what you get from your average gasoline-engine car. That would be real nice!

100kWh is also equal to 341,000 Btu, that is if you like to use the British system of units. At about 10,000 Btu to run a home-sized air conditioning unit, this battery will provide you 34 hours of uninterrupted cool air. It it also equal to 3.4 US Therms (each Therm is equal to 100 cubic feet of natural gas), sufficient to heat a California home in the winter for about 4 days.

Now let’s get a little more creative in this comparison exercise. This high amount of energy can be quite explosive if not designed and operated properly and safely; 100 kWh is the same amount of energy delivered in 86 kg (190 lbs) of TNT….enough to level an entire building.

On a more cheerful note, this battery packs the equivalent energy of 86,000 kilocalories, or what an average human consumes in food over 43 days!

Yet as big as this figure sounds, and it is big, only 3 gallons of gasoline (11 liters) pack the same amount of energy. Whereas the Tesla battery weighs about 1300 lbs (590 kg), 3 gallons of gasoline weigh a mere 18 lbs (8 kg). This illustrates the concept of energy density: a lithium-ion battery is 74X less dense than gasoline.

19Aug 2016

As I pondered over the past couple of weeks what might be a befitting topic for this 100th post, a group at MIT announced that they discovered how to make batteries with double the energy. Of course, the operative word in the press release was “first-prototype” which means that it might be a long while before, that is if, we see commercial deployment. However this announcement was the catalyst to focus this post on the state of the lithium-ion battery: In other words, if we ignored future inventions, what is the best that we can expect from the lithium-ion battery today across a number of applications.

For the vast majority of modern applications, the lithium-ion battery is capable of delivering the requisite performance. So if you are wondering why is it that most users complain about the battery, I will use an analogy of a jigsaw puzzle. The solution to storing electrical energy involves many pieces, like the pieces of a jigsaw puzzle. These pieces include the battery materials, chemistry and design, which is often provided by one party: the battery manufacturer. But also a critical piece includes the power management of the device and system, in particular the electronics and software needed to monitor how the energy is efficiently used, say by the apps on your smartphone. An equally critical piece is the battery management intelligence, which is what we do here at Qnovo, that is responsible for the integrity and efficient operation of the battery. If water use is to represent energy use, then the battery is the reservoir; power management is akin to water conservation, something we, Californians, are familiar with; and battery management is ensuring the integrity of the reservoir and its contents, making it large and free of toxins.

Separately and individually, each piece of the jigsaw puzzle is today at an exceptional state of the art for consumer electronics, energy storage, and electric vehicles. For example, energy density of batteries in commercial deployment is already near or at 700 Wh/l. This energy density is sufficient to power smartphones comfortably for a full day of use, or power an electric vehicle for 300 miles. Power management has become quite sophisticated, especially in consumer electronics where now the operating systems, e.g., Android OS and iOS, are asserting clever decisions on how apps may use power. Battery management intelligence has also become quite sophisticated, peering deep into the battery in real time and ensuring its continued health and integrity under extreme operating conditions.

But now imagine for a moment trying to build a jigsaw puzzle where multiple players share in putting the puzzle together, or worse yet, each player owns a subset of the puzzle pieces, but not all the pieces. Now you can imagine that putting the puzzle together can get quite complicated. You see, battery vendors know how to build the battery itself but tend to be quite novices in power management and battery management intelligence. System integrators and OEMs tend to have plenty of experience in power management but their knowledge of the battery chemistry tends to be limited. As to battery management, both battery vendors and OEMs have historically under-estimated its need and are playing catch up.

This, for example, begins to explain why Tesla Motors wants to own all these three pieces of the puzzle, beginning with their widely discussed Gigafactory but also their less-advertised efforts in power management and battery management. Apple is also in the same league. While Apple does not manufacture their own batteries, it is widely known that Apple does design their own batteries as well as having growing expertise in both power and battery management. But these tend to be early adopters who have recognized that they need to lead in owning and putting the pieces of the puzzle together. There are other giants who are in need of playing catch up, and they include the likes of Google, Microsoft, Facebook…as well as industrial players who are eyeing batteries for stationary energy storage and electric vehicles. Gradually, they are all beginning to make power and battery management integral to their long-term strategies.

Historically, system integrators and OEMs treated the battery as yet another component they source from suppliers, like the display or other electrical or mechanical components. But this model of outsourcing the battery expertise is beginning to fray. First, battery vendors are hitting the limits of materials and are struggling to meet the increasing demands of their customers without the use of intelligent power and battery management algorithms. Second, there is a growing discomfort, and I might dare say mistrust, between the OEMs and system integrators on one side, and the battery vendors on the other. Third, with the advent of cheap, meaning both inexpensive and lower quality, batteries form China, the business model of the traditional battery vendors, in particular Sony Energy, Samsung SDI, LG Chem is under pressure. A quick evaluation of their financials is sufficient to show they are not healthy. Sony recently announced the sale of their battery business to Murata Manufacturing. These shifting dynamics complicate the necessary tasks required to put together this battery puzzle and are forcing participating companies to seek different alliances.  For example, see the growing alliance between Tesla and Panasonic as well as between GM and LG Chem. In China, witness the growing influence of BYD in making batteries and making electric vehicles. The result is that the optimal battery system that incorporates the right battery, right power management intelligence, and right battery management intelligence is accessible to limited few organizations that either have the means to be vertically integrated or put together the necessary alliances.

As the reader can gather, the challenges in offering a great battery experience is really not technical in nature, but rather have economic and organizational origins. For consumer applications, the technology already exists to build elegant smartphones with battery capacities in excess of 3,000 mAh, charging very fast at 1 to 1.5C, and lasting 800 to 1,000 cycles. These specifications give the average consumer an excellent overall battery experience. For energy storage, the challenge is not the battery chemistry but rather hitting the right price points and building out comfort in the specifications from extensive testing. For electric vehicles, the cost of the battery is rapidly dropping. The Chevy Bolt and the promised Tesla Model 3 are prime examples of vehicles targeting the broader population at an increasingly affordable price. That is not to say that engineering innovations and continued disciplined product improvements are not necessary; they are important. But the perception that the battery industry is in dire need of a large breakthrough in technology and materials is not well founded. Instead, there is a bigger need for all the players around the battery jigsaw to learn to work together and leverage each other’s expertise and technologies. This is happening; in the process, we will continue to see a race to build up intellectual property, patent ownership, expertise, and skills by the various participants.