26. HOW TEMPERATURE WREAKS HAVOC ON YOUR BATTERY.       

You probably suspected that temperature swings are not good for your lithium-ion battery. But what is the extent of the damage, and what are the temperature limits that one should attempt to follow? This is the subject of today's post.

If you were to review a specification sheet for a lithium-ion battery, it most often has a few (but not too many) things to say about temperature. Incidentally, it will take a great deal of effort and investigation for you to find a specification sheet that corresponds to the battery in your mobile device. These documents are usually not provided by the battery vendors to end users. 

Usually, the specifications will list the test conditions. The vast majority of battery tests are usually conducted in a laboratory with a controlled environment, and a temperature typically between 22 °C and 28 °C (equivalent to 72 °F to 82 °F). The specifications will also provide some additional conditions at temperature extremes such as below 10 °C or above 45 °C. For example, it will state the dependence of the battery capacity on temperature. The following chart shows the dependence of capacity on temperature for a typical polymer lithium-ion battery based on the specification from the battery manufacturer. One can see that the battery is "happiest" near 25 °C to 35 °C (or near 75 °F to 95 °F). Note that this is the internal temperature of the battery itself, not that of the outside case of the mobile device.

The available maximum capacity of the battery has a strong dependence on temperature.

The specifications will seldom provide the effect of temperature on the battery health and its cycle life. Tests have repeatedly shown that the cycle life of the battery tends to degrade with temperature. At temperatures below 15 °C, the cycle life drops very fast. That's because the lithium ions find it increasingly difficult to make the journey from one electrode to the other at colder temperatures. At higher temperatures, this "ion mobility" is improved and tests show that cycle life is improved up to a point, somewhere near 45 - 50 °C. At such high temperatures, several materials such as the electrolyte begin to decompose causing a rapid degradation of the battery. The following chart exhibits this effect. This particular polymer battery exhibits an excellent capacity retention of its capacity when cycled at 45 °C, but as soon as its temperature is raised to 55 °C, its capacity fades at an alarming rate.

So what practices should you take away? Clearly, avoid operating in temperature extremes. For example, charging your phone on your car dashboard in the middle of the summer heat will undoubtedly cause your battery lots of health problems. 

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

25. WHAT HAPPENS AFTER 80% ?                                                    

I wrote in a previous post that the standard for a dead battery -- at which point it should be replaced -- is 80% of its original capacity as a newly manufactured battery. Why is that? Is this a random value or is it based on a valid rationale?

At the surface of it, this question may seem benign, but it is not and its consequences can be quite severe.

The cycle life specification of a lithium-ion battery is defined as the number of charge-discharge cycles this particular battery can support until it reaches 80% of its original capacity. The capacity of the battery fades (decreases) with every charge and discharge cycle. This cycle life performance (number of cycles) is ultimately what determines whether a battery, and its host mobile device, is subject to a warranty return. 

One attempt at cheating around this specification -- and consequently the warranty claim -- is to reduce this threshold down to say 70%...in other words, to deem the battery dead when it reaches 70% of its original capacity, not 80%! This attempts to artificially add a few extra cycles to the life of the battery and to push out the burden of a warranty claim merited at the higher threshold. Therefore, the question becomes: What happens to the capacity loss between 80% and 70% (or even lower)?

As it turns out, tests have shown that the battery capacity loss tends to accelerate past 80%. In other words, the battery loses its capacity at a very fast rate once it passes the 80% threshold. This renders the battery quite useless once the capacity drops past 80%. The cycle life fade in the following chart illustrates an extreme case where the battery loses its capacity at a very fast rate past 80%. In this particular case, the battery appears to hold its capacity well but right around 400 cycles, the performance turns very poor and the battery loses its capacity quite rapidly.

While this rate of capacity loss may be an extreme case, most batteries seem to accelerate their capacity loss past 80%. Furthermore, this rapid capacity loss may be accompanied by an increased likelihood of lithium metal plating. In other words, a dead battery with its capacity past 80% becomes a serious fire hazard !

Additionally, with this rapid loss of capacity (and increasing age), the battery begins to swell -- its thickness rapidly increases and can cause serious physical damage to your mobile device. 

So in summary, if your battery capacity drops to near 80%, you should seriously consider changing it. If it happens within the 2-year warranty window (in some locations, it is sadly one year), return the phone and the battery to its manufacturer.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

24. THE BATTERY INDUSTRY IS HITTING THE WALL!                          

I am an avid photographer. I have been one for a long time. My first camera was vintage ca. 1968. Its body was simple. It had a mechanical shutter; no battery; no metering; no autofocus....but I was proud of the lenses that I accumulated over the years; I labored summer jobs to pay for my expensive lenses. Photography was all about the quality of your lens. Photography was also only for the few who really cared about photography. 

Fast forward to 2014. Your average smartphone has a built-in camera. The cameras in an iPhone 6 or 6 Plus or a Sony Xperia Z3 are exceptional. They make it easy for the average consumer to take exceptional photographs. We democratized photography: these simple cameras made photography readily accessible and easy to use for the masses.

Yet, the quality of the optics in these new built-in cameras are nowhere the quality of the lenses in our earlier SLR cameras. To begin with, they are far smaller...and in optics, small = bad! They are also far cheaper. So, how is it that they can take such great photographs?

You see, every smartphone includes plenty of computational power, far bigger than the PCs of earlier eras. These modern built-in "cheap" cameras contain a substantial amount of intelligence and computation that correct many errors from optical aberrations in the lenses to handshake and color purity. Lenses in today's smartphones are not of the highest optical quality, yet the errors in the optics are more than compensated for by the electronics and software in your smartphone. The result is staggering: Lower cost, higher quality photography.

Is there an analogy here to batteries? yes, of course. 

The lithium-ion battery industry is losing steam in its quest to increase energy density. For several years, it has been humming along at an annual growth pace of 6% -- which incidentally has proven to be insufficient to keep pace with the need of mobile devices. Now, the materials used in the lithium-ion battery are reaching their theoretical limits. A breakthrough in materials is needed, yet, while some technologies are promising, little is on the immediate horizon for commercial release. Manufacturing processes have also gotten more complex and more expensive. But the industry cannot sustain higher-priced batteries. New and small battery vendors out of China are providing batteries with lower quality but also far lower price points. 

The large and main battery vendors are trying hard to push the limit on energy density and are often coming up short. Instead they resort to compromises, living the whack-a-mole life. To get more energy density, they sacrifice cycle life. To gain cycle life, they sacrifice charge times....etc. Additionally, manufacturing billions of batteries with tight quality is becoming challenging. Unlike integrated circuits where manufacturing is incredibly reproducible, no two batteries are ever born equal; there are significant manufacturing variations from battery to battery, even from the same factory and the same manufacturer. 

The graph below shows statistics on a dozen batteries of the same type and vendor, all from a smartphone model made by a well recognized manufacturer. Nominally rated at 2,500 mAh, this distribution represents the spread in capacity after only 500 cycles (or a little over a year of use); yet these batteries were all supposed to be the "same." The spread is enormous and highlights the manufacturing variations in batteries. This graph also tells you a scary story: you may be unlucky and  have a battery in your smartphone with nearly 1,800 mAh of remaining capacity after some use, not the 2,500 mAh that you were promised initially!

So no surprise that the large handset manufacturers are growing frustrated with the large battery manufacturers. Several of them are taking matters into their hands. It is no secret that Apple has been hiring battery engineers for several years now.

Yet, what remains puzzling is that the battery industry cannot seem to learn from other industries, for example, from the camera industry. There is an enormous opportunity to enable algorithms and software solutions that can correct for the shortcomings in batteries. For example, use algorithms that can adapt to manufacturing variations in the battery and increase its cycle life and reduce its charge time...in other words, shift the burden away from improving manufacturing and materials to computational algorithms that can correct for some of the battery's shortcomings. After all, there is plenty of computational horsepower available, and it is quite inexpensive.

But why is it that battery vendors are not taking the initiative here ? There is no hard evidence but I suspect two reasons. First, such new solutions require a new set of skills bringing together battery chemists and software engineers. The main large battery manufacturers lack this particular combination. I reckon this is not easy to accomplish -- it took us a while to build our multidisciplinary battery+software team of engineers at Qnovo, and build a culture of collaboration between these two disciplines. Second, the established battery vendors have a long legacy of building chemistry and chemical products. This operational discipline is immensely respectable. But it is their operational success that is also their Achille's heel; their past culture makes it difficult for them to explore radically alternative solutions than the ones they have been accustomed to for the past decades.

The path that the battery industry has been on is facing serious challenges. The frustration among consumers and handset manufacturers about the battery will not disappear. It's only getting worse. This industry is ripe for some serious innovation.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

23. KIDS, DON'T DO THIS AT HOME !                                                     

The new iPad Air 2 is a beauty, isn't it? At 6.1 mm thick, it is nearly feather light. The new iPhone 6 is 6.9 mm. The Android competition is not far behind. The race to make ultra thin smartphones and tablets is on. Thin is in...but certainly not easy !

One very important design parameter in making thin devices is the thickness of the battery. An iPhone 5S is 7.6 mm while its battery is nearly 3.6 mm. That's nearly half the thickness of the iPhone 5S, and probably more for the iPhone 6.

So, why can't we make batteries thinner? Three critical factors come into play.

1. Swelling: Yes, yes, lithium-ion batteries swell and grow. It's a complex chemical process within the battery that makes the battery grow thicker with usage and age. Take a look at the photograph below. It is of a battery from one of the top handset manufacturers -- we shall keep it nameless here. This particular battery has reached its cycle life and age limit, and as the photograph shows, it has swollen enormously. If you ever suspect that your battery is swelling inside your device, take it immediately to a disposal facility that can handle hazardous materials. 

Most handset makers allow for a 10% swelling margin in their designs. So let's say that the battery nominal thickness is 4 mm; then the mobile handset maker will typically allow for 4.4 mm in their designs. That's one limitation to overcome.

2. Safety, and more safety: The photograph above shows a lithium-ion polymer battery. A polymer battery typically encapsulates the active chemical materials in a thin plastic-like pouch. This pouch has very little mechanical rigidity and consequently, can be easily pierced with a sharp object. If you recall from an earlier post, piercing a battery can cause a fire. Therefore, a lithium-ion polymer battery has to sit in a protective case. Smartphones and tablets that use non-replaceable batteries use their own chassis as the protective case. In other words, the smartphone itself protects the battery from external damage. In devices where the battery can be replaced by the user, you will note that the battery is encapsulated in a rigid protective metal casing that adds further thickness to the battery. This is one of the reasons many handset makers have elected to embed the battery inside the mobile device and make it not possible to be replaced by the consumer.

3. This darn energy density again: As I mentioned in a previous post, a lithium-ion battery contains electrodes, electrolyte and several other components that don't directly contribute to storing energy. As the battery gets thinner, these additional components begin to act like "design overhead." Consequently, the energy density begins to substantially drop. In other words, a thin battery makes it awfully more difficult to maintain a large capacity.

There you have it...three forces that conspire to make the battery and the mobile device thicker than what handset designers would like to achieve. This is yet another example of how the battery industry has lagged in its specifications and innovation behind the fast-moving mobile industry...and further reason why the relationship between battery vendors and handset makers will only get more tense in the future.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

22. WHICH SMARTPHONE CHARGES THE FASTEST?                    

My prior posts are begging for today's post: "Mirror, mirror on the wall, who's the fastest of them all?"

Yes, you guessed it right, not all mobile smartphones are created, ehem, designed equally. Yes, some are designed in Cupertino, others in Taipei or Tokyo or Seoul, and many somewhere in China, and they all seem to share many common features such as a processor, radio modems and a beautiful screen with lots of pixels....but when it comes to power and charging, the designs vary vastly. It's because power and battery don't like to adhere to standards. The temptations for engineers to design and redesign the power path is too great. To their credit, there is not one-size-fits-all when it comes to power and charging. Let me give you an example, changing the charging current from 1A to a mere 2A is plenty reason to wreak havoc on the design. The thermal design will most certainly be different. Some components such as inductors will have to be selected with greater care. Electrical resistance in the path to the battery will probably have to be cut in half! With these tasks, it is normal to expect some smartphone makers to be more bold than others about introducing fast charging. But in all cases, expect to see more introductions in the coming year or two.

Battery charging has an inherent safety limitation built into the software and hardware: the charging voltage of the battery may not exceed 4.35 Volts! This bears a serious consequence: the charging current must be scaled back when the battery begins to approach getting full. I will leave the details to another discussion, but for now, an average consumer will observe this limit as a slower charging once the battery meter on the smartphone begins to exceed somewhere between 60 and 80%. Consequently, the device charges at its fastest rate when it is mostly empty, which is exactly when you also want it to be at its fastest -- you find yourself at the airport and your battery is about to die; or you are rushing to a morning event and you realize that you forgot to charge your device overnight!

Consequently, one useful metric of charging speed is the time it takes to go from zero (empty) to 50% (half-full). The fastest charging smartphone on the market today is from a small company out of China called Oppo. Their device is labeled the Find 7 -- one can buy it directly from their China store, but beware, its radio bands are not fully compatible with many network bands in the US, especially AT&T and Verizon.

So mirror, mirror on the wall, what device thou shalt recommend after all? If charging times are important to you, you should be able by now to make your own informed decision. If you can't find a satisfactory product that meets your wish list, let your favorite wireless carrier hear from you, in person at their store, or on your favorite social network.  But one thing is certain, once you get used to fast charging, there is never returning back to regular charging, or should I rather say, slow charging!

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

21. DECIPHERING CLAIMS OF CHARGE TIMES.                          

Samsung recently announced their new Note 4 with a claim that it charges from zero to 50% in thirty-ish minutes. What is thirty-ish? Is it 31 or 39?  Motorola also announced that their newest Moto X will provide 6 hours of mixed use after only 15 minutes of charge. Mixed use, as Motorola defines it, includes a mix of actual use time as well as standby for an average user. Hmmm....this is not very specific! Let's see if we can decipher some of these claims in this post and shed more light on what these handsets are accomplishing.

Let's establish a few fundamentals that relate charge current, and consequently electrical power, with charge time. I will try to keep it simple enough for many readers to understand. 

First, we need to establish the C-rate. It should be fairly intuitive that more electrical current and power from the AC wall adapter into the battery should mean faster charging. To read the rating of your AC wall adapter, look at the fine print on the adapter itself and it will tell you the wattage (e.g., 5 Watts) and the output current (e.g., 1 A at 5 V). In this particular case, the charging current is about 1 A. This charging current should be measured relative to the capacity of the battery to establish charge time. For example, a charging current of 1 A will charge a 1,000-mAh battery far faster than it will charge a 3,000-mAh battery. So we define a new relative measure called the C-rate: It is the charging current divided by the capacity of the battery. So if the charging current is 1 A and the battery capacity is 1 Ah (1,000 mAh), then the C-rate is 1 A/1 Ah = 1 C. If the charging current is 1 A but the battery capacity is 3 Ah (3,000 mAh), the the C-rate is 1 / 3 = 0.33 C. The higher the C-rate, the faster the charging. So let's take an example of a real-life smartphone: the iPhone 5S. Its AC wall adapter has an output rating of 1 A at 5 V (which you can read between the prongs of the little adapter cube). Its battery is rated at 1.55 Ah (1,550 mAh). You can't see this unless you open your phone back cover; alternatively, you can google the capacity of the phone. So, the C-rate of an iPhone 5S is 1/1.55 = 0.65 C. So far, this should be fairly straightforward.

Second, let's convert C-rate into charge times. This conversion table makes it quite easy.

Approximate charge times for a lithium-ion battery for particular charging C-rates.

So one can see that the higher the C-rate, the faster the charging. The numbers may vary a little from battery to battery, but these figures give you a fairly reasonable estimate.

Now, let's go back to the Note 4 and see if we can decipher its claims. Samsung claims zero to 50% in  thirty-ish minutes. From the table, we see that 30 minutes would be equivalent to 1 C, but 39 minutes would be closer to 0.75 C. Given that the published capacity of the Note 4 is 3,200 mAh, the range of charging current would be 2.4 A up to 3.2 A. The corresponding AC wall adapter wattage rating would be in the range of 12 W up to 16 W. I have not seen yet an AC adapter for the Note 4, but if you have one, you can confirm the wattage and the charging current, and consequently the charge time.

For the Moto X, the claim is more tricky. The Moto X has a published capacity of 2,300 mAh. Motorola's website claims that this capacity should last the average user up to 24 hours of mixed used. Therefore, if a 15-minute charge gives the user 6 hours of mixed used, one can estimate that this quick charge provides 6 / 24 = 25% battery capacity, or consequently, it will take 30 minutes to get to 50%. Based on the table above, this corresponds to 1 C or a charging current of 2.3 A, and a wall adapter rated at or near 12 W.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

20. WHAT'S THIS FUSS ABOUT CHARGING?                                     

Charging your mobile device's battery was pretty much a non-issue for many years...customers seldom complained; manufacturers did not see charging as a limitation; and charging, well, was really not a problem.

That began to change in the past year or two. Several factors are converging to elevate battery charging to a whole new level of importance and complexity. So what are these factors:

1. The rise in battery capacity has made charging painfully slow. Early cell phones and smartphones had batteries that lasted days, but the newest smartphones now sport large capacity batteries (up to 3,200 mAh) and are charging using the same 5-Watt AC wall adapter that shipped with the smaller smartphones 5 years ago. The result: It takes hours to charge the newest smartphones. In technical terms, this is called the C-rate. A 3,200 mAh packs 12.2 Watt-hours of stored electrical energy. Dividing the power of the AC adapter by the energy of the battery gives the charging C-rate, in this case, 5 divided by 12.2 equals 0.4C, which equates to 3 hours or more of charge time. In contrast, batteries from earlier generations of mobile devices charged at twice that rate, somewhere near 0.7C. So there has been a drive in the industry to increase the power of AC wall adapters and increase charging rates.
2. The rise of energy density makes charging more complex: As I mentioned in a previous post,  increasing charge rates at these higher energy densities have a serious impact on cycle life, effectively reducing the battery warranty. In other words, the simple charging methodologies of earlier generations of mobile devices are not applicable to charging the newest generation of smartphone batteries. Therefore, charging newer mobile devices at higher charge rates (in order to reduce charge times) now involves newer designs and methodologies for charging -- otherwise, you can charge fast, but your battery will not last! That is not an acceptable compromise.
3. Consumers asking for super fast charging: End users and consumers are now beginning to realize that if batteries cannot have battery capacities that can last several days, if not weeks, then they should have the ability to charge their batteries at blazing fast speeds; certainly faster than 30 minutes, and possibly 15 minutes if possible. These kinds of charge times are equivalent to charge rates in the range of 1.5C to 3.0C, in other words, about 4 to 10X faster than presently shipping in smartphones. Naturally, at these super fast charge rates, the design of the entire battery charging circuitry and methodologies need to be conceived from scratch to allow for the extra charging power and to deliver sufficient battery cycle life (and battery warranty).

Handset manufacturers are beginning to recognize these factors and why fast charging should become an important part of the mobile experience. It is a major transformation for them -- new designs for their charging platforms are required and that is not trivial. But that train has left the station, and handset makers who are not taking action will miss the boat. The first shot across the bow came from a small but promising handset maker in China called Oppo. They released in early 2014 the first smartphone that is capable of charging at 1.5C. Expect to see more mobile device makers to follow suit.

In future posts, I will talk more about the metrics of fast charging, especially as mobile handset makers will begin to make claims about charge times that may be confusing.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

19. I WANT MORE BATTERY CAPACITY IN MY SMARTPHONE.             

You own the newest smartphone model; you love its screen; it has a very fast processor; you are a power user and you are glued to your device....but you are unhappy with the battery. You ask "Why can't I get a battery with larger capacity?", but no one seems to listen or give you a satisfactory answer.

The simple reason is embedded in two words: Energy Density. It's not large enough and it's not growing fast enough.

What is energy density? As the name implies, it is the amount of electrical energy, measured in Watt-hours, contained or stored in a given volume, usually in liters. The most common unit of energy for batteries is Watt-hours per liter, abbreviated as Wh/l. If you don't like this unit, then you can convert it to other units such as Joules per cubic meter or even btu per pony if you so desire!

Why does energy density matter? If you desire a larger battery capacity without growing the size of your smartphone, then you need to pack more energy into the same battery dimensions, which means your energy density should grow. 

A state-of-the-art lithium-ion battery has an energy density of approximately 600 Wh/l; that's the energy density of a typical 3,000 mAh battery in your smartphone. To grow the battery capacity to 4,000 mAh without getting a physically larger smartphone, the energy density will need to grow to 800 Wh/l. That's where the problems begin to pile.

Historically, energy density in lithium-ion batteries has grown very little. From 1995 to 2014, energy density grew at a slow annual pace of about 6%. This is not unusual. Innovations in new materials require time and a lot of capital. Yet, the performance of a smartphone and the ensuing insatiable demand for more battery has grown at a far faster pace. For example, an iPhone 6 introduced in 2014 is about 50X faster than the first iPhone introduced in 2007, yet energy density has grown by only 1.3X over that same period.

Energy density has increased by a mere 1.3X since the introduction of the first iPhone in 2007.

So, when should we expect to reach an energy density capable of delivering 4,000 mAh in a standard 5-in smartphone ? At the rate we have been going, not before 2020 ! 

But the situation may be far more dire. You see, the present material system of lithium-ion batteries uses carbon-based electrodes. This system has already reached its energy density limit, somewhere near 600 to 650 Wh/l. There are promising new materials that can potentially provide fuel for future growth, but the development and manufacturing challenges remain quite significant. Any delay in the development of these new materials could further delay the potential introduction of batteries with high capacities.

Until then, learn to live with capacities near 3,000 mAh, or use a physically larger mobile device that is able to sport a physically larger battery. Neither is an attractive solution...so now you understand why the battery is headed to become the #1 consumer problem in mobile devices.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

18. YOUR GUIDE TO SELECTING A MOBILE BATTERY.                

So you decided to buy a new mobile smartphone. You researched the internet; you looked at the web reviews; you have decided on what OS you prefer, iOS, Android or even Windows; you looked at the quality of the built-in cameras and you know how many megapixels you want....and then, you quickly come to a HALT! You are now asking about the battery: "Is it going to last me?"... but you can't seem to get a straight answer. Instead, you see different claims from different handset makers, and you can't even begin to compare the claims. This post is intended to shed more light on your decision.

First, most claims by handset makers are only a general guideline. They are careful for not saying too much for fear of not meeting the expectation they are about to set; then they are careful for saying too little for it means nothing to the consumer. So their claims wind up in the middle with enough language to give them plenty of outs but be no more than a vague guideline to you.  For example, Apple claims "up to 11 hours on WiFi" with the operative disclaimer being "up to." Motorola claims its Moto X will last "up to 24 hours of mixed usage" where the fine print at the bottom describes it as based on an average user for both use and standby. What is an average user? Are you an average user? and what is the mix of standby time and use time? So these numbers are not terribly useful for you in your purchasing decision. In fairness to the device manufacturers, the task of giving an accurate battery time is not easy because of the diversity of user behavior, but solutions do exist...I wish they were more proactive in implementing them!

Here are some points you may want to consider as you identify a battery that matches your personal needs:

1. Capacity: First, forget about claims of time. Focus primarily on capacity in mAh. For Apple phones, the iPhone 6 has a capacity of about 1,800 mAh whereas the iPhone 6 Plus has a capacity of nearly 2,900 mAh. In the Android universe, a Moto X has a capacity of 2,300 mAh whereas a Sony Xperia Z3v has approximately 3,100 mAh. More is better! More mAh is more hours of use. It is simple.

2. Compare capacities only within the same class of devices: This is not as complicated as it sounds. First, compare only a battery from an Android phone vs. another Android phone. Comparing the battery capacity of an iPhone to another Android phone will not be very reliable. Second, compare batteries across devices with similar screen dimensions. So compare a 5-in screen device vs. another 5-in screen devices (or within a ¼-in in either direction). But be careful to not compare a 4-in screen with a 6-in screen device. The larger the screen, the more power it needs, and the bigger the battery requirement. Third, compare devices with similar processor speed. Within the Qualcomm family of processors, smartphones that use the Snapdragon™8xx architecture require a bigger battery than smartphones that use the less capable Snapdragon™4xx architecture. For example, a Moto X has a more capable processor than the Moto G; hence the Moto X requires a larger battery to achieve the same battery life as the Moto G. Similarly, a larger screen requires a bigger battery than a smaller screen.

3. Understand your own usage pattern: Some of us are casual users who use their mobile device for occasional e-mails, texting and phone calls; others are traveling business executives constantly on their devices; of course, the younger generation who may be glued to their favorite social networking app will have yet a different usage profile. If you are a casual user, you will most likely be plenty served with a battery capacity in the range of 1,800 to 2,300 mAh. If your phone capacity dips a little in the day, plug it in...you are probably close to an outlet most of the time. If you are an executive who needs the smartphone (and especially the screen) on constantly, then go for the largest capacity you can find. Right now, 3,000 to 3,200 mAh are available across a class of Android smartphones. The iPhone 6 Plus is at 2,900 mAh. Batteries at such capacities seem to be capable of lasting at least one day of heavy use. My Sony Xperia Z2 (3,200 mAh) lasts me comfortably through an entire day, from early morning to late in the evening. A teenager who likes their social networking apps will also require a battery with a capacity preferably above 2,500 mAh (or they will have to charge more than once a day). Think of it this way, if you have a fast processor +  your screen is on most of the time + you are downloading/uploading data constantly, then you most likely need a battery with the largest possible capacity.

4. Not all smartphones are created equally: So let's say you find two smartphones with similar processors, similar screen dimensions, and similar battery capacity. Which one do you pick? Some manufacturers are better in power management than others. This is where you want to look at standardized tests from various websites that will indicate how a Sony for example compares relative to a Samsung or HTC or LG. Generally speaking, Apple, Sony and to a lesser extent Samsung have shown better power savings in their designs than other manufacturers.

5. Ask for the charge time: Manufacturers tend to be shy about disclosing their battery charge time. If and when they do, the claims are a little murky. That's because charge time is tricky: some manufacturers slow down the charge time to extend cycle life (i.e., the longevity of your battery). Other manufacturers will light up the green (battery full) light at or near 90% not 100%. The fastest phones today charge in the neighborhood of 2 to 2.5 hours. Others can take as long as 4 hours to charge. Visit AnandTech reviews...they are one of few internet sites that publish measured charge times.

6. Ask, if you can, about cycle life: I say, if you can, because manufacturers will go out of their way to hide their cycle life performance. For some of them, it's nothing to write home about. If you are in the US and use the Verizon network, chances are your phone is specified to last 800 cycles (or about 2 years if you charge once daily)....but it's difficult to verify. If you are on AT&T or other North American networks, your phone will most likely be specified to meet only 500 cycles. A cycle life specification of less than 800 cycles means, especially for the power users among us, that in less than 6 months of usage, you are likely to notice a significant drop in battery life. In other words, you will likely wake up after a few months of use and realize that your smartphone is no longer lasting you a full day. Worse yet, if you find yourself charging more than once a day, then even 800 cycles are not enough -- you will suffer serious loss of capacity within a few months or less. Don't make a mistake and buy a phone that you will regret after a few months of usage.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

17. MEDIA AND BATTERIES: MANIA OR EDUCATION ?                

We are happy and flattered by Antony Leather's report today in Forbes on Qnovo's fast charging. A self-described passionate of gadgets, Antony understands many of the subtleties of the batteries and their challenges in mobile devices.

The media is now paying a lot more attention to the battery. Several sites publish thorough tests of batteries and their performance. For example, sites such as GSM Arena and AnandTech perform battery tests on different types of devices to quantify the number of hours a consumer should realistically expect to obtain. Considering that the claims of battery life from the device manufacturers are often met with skepticism, these independent tests can be quite useful and insightful.

Until recently, such independent tests were mostly focused on battery life; in other words, the number of hours for talking on the phone, or web browsing, or watching a video...before the battery was required to be charged. Some sites are now beginning to test for charge times. Slowly, some reports are now beginning to look into battery longevity and cycle  life -- the ability of a device to hold charge after a few months of use is now beginning to get noticed by end consumers. In all cases, these tests and rigor will aim to keep the mobile device makers and the battery vendors a little more honest about their claims.

Of course, in contrast to some of these useful independent tests and reports, the media and the internet also carries news and press releases about new breakthroughs in batteries without vetting out the sources or the veracity of the claims. This tends to create a short-lived attention for the source, but generates very little in educating the public on the battery. 

As the battery is rapidly climbing to become one of the top challenges in mobile devices, the media can play a very productive role in educating itself and the public about the battery. Reports and demonstrations such as the ones done by Antony Leather give its audience useful insight and background. You, as a reader and user of mobile devices, will also benefit immensely in wisely making your purchase decision about your next mobile device if you are able to find appropriate education material and sites that can be trusted with their tests, reports and explanations.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com

16. THERE IS NO SUCH THING AS A FREE LUNCH!                                                 

I was greatly entertained to read about a newly reported discovery from Nanyang Technology University claiming a new battery that can charge to 70% in a mere 2 minutes, yet last 20 years, or about 10,000 cycles. There were recent reports in the media for similar claims from StoreDot; that battery was charged at an even faster rate of only 30 seconds. Every so often, we hear similar reports about breakthroughs in batteries, yet reality tells us otherwise.

First, let's do some simple math. Let's look at the required power to charge a battery in a very fast time window. If we assume a lithium-ion battery with a very modest capacity of 2,000 mAh typical of 2013-vintage smartphones, and require to charge it in 1 minute, we find that the charging power requirement is in excess of 450 Watts. In other words, we require a massive power supply, not your standard off the shelf AC wall adapter, to provide the required charging power into this mobile device. Considering that most charging systems have at best an efficiency of about 90%, this translates to nearly 45 Watts of heat dissipated into your mobile device. Let me translate that into more practical terms: Your smartphone including its battery will just vaporize if you dare put 45 Watts of heat into it!!! And we haven't even looked into the chemistry yet.

Let's put another arrow into this dying beast. A typical lithium ion polymer battery in a standard smartphone carries a current density in the range of 1 to 3 milliamps per square centimeter (abbreviated as mA/cm2). In other words, if one were to hypothetically slice through the electrodes while being charged, one you find that each cm2 of cross-sectional area carries about 1 to 3 mA. Why is this meaningful? Batteries and its materials have upper limits of how much current they can realistically carry.  At higher current densities, lots of bad things happen. Bad reactions accelerate; materials decompose; local heating damages the internal structure; safety concerns are enormous...etc. For a lithium ion battery including its thin electrodes and its electrolyte, the limit is about 5 milliamps for each cm2. Even in the most optimistic scenario where materials capabilities improve by 10X in the next decade, we are still looking at a best case limit of 50 mA/cm2.

So what is the current density to charge a 2,000 mAh in 1 minute?  About 200 mA/cm2! In other words, the inner materials of a typical battery will be fried almost instantaneously at such current densities. Additionally, at such currents, even the hint of an electrical resistance in the electrical path is enough to eliminate any notion of meaningful charging.

I am certain that one of my esteemed readers will suggest reducing the capacity of the battery to a few mAh instead of 2,000 mAh and thereby reduce the power and current. Sure, one can do so but a few mAh battery does not offer much useful power to begin with. Another reader may suggest making the areas larger to reduce these densities. Sure, again one can do that, but that you would eliminate the volume advantage offered by high-energy density batteries; in other words, portability and mobility will be lost.

Of course, this is not to say that the science behind these claims is bogus. There is plenty of great material research being conducted at the nano and molecular level aimed at improving the rate at which these novel materials can accept charge. But going from such basic material research to making enormous claims about the battery and its charging speed at the system level is stretching scientific credibility by a loooooong mile!

Naturally, the big question is "who cares about charging a battery in 1 minute?" Well, I cannot think of many, if any, applications that require that kind of speed, at least not yet. Charging in 15 minutes would most likely be plenty fast to most applications, and guess what, it is very possible without having to change the material paradigm of present-day batteries.

The moral of today's post: Beware of big and utopian claims about batteries. They most likely are not true or at least are many years away from realization.

© Qnovo, Inc. 2014 / @QNOVOcorp @nadimmaluf #QNOVOCorp    http://www.qnovo.com