Mobile devices

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.

18Apr 2018

5G is the evolution of the present LTE wireless network that carriers are beginning to deploy later this year. 

Yes, it will be a Global network, with every geography around the globe utilizing it at some point in the future. 

Yes, it will have Great capabilities, from streaming videos with very little if any delay, and seamlessly handle a large number of connected devices such as sensors.

Yes, it will Galvanize a new set of applications that may have not even been conceived of yet. Just imagine what the previous generations did to promote social networks, video, and other such uses that were not possible a decade ago.

Yes, it will have Grave consequences on the battery. The demands that the network places on the devices, in particular, the handset or smartphone, are significant. Early results show that the power consumption in the chipsets that run smartphones are higher by as much as 25 to 50%.

Yes, the effort will be Grueling to improve the battery’s performance and safety.

Much has been written about 5G and its planned deployment. Unfortunately, the coverage tends to be centered on the benefits of 5G and neglects the impact on the battery. If anything, it can be misleading in promising a longer battery life, contrary to the present data.

The figure below (courtesy of Verizon Wireless) highlights three main thrusts of 5G. At the low frequency bands, typically between 600 MHz and 900 MHz, 5G will continue to provide mobile broadband, similar to 4G / LTE connectivity on your smartphone or handset device. At these frequencies, the network will be limited by physics to maximum data bandwidths on the order of a few hundred Mbits per second.

 

 

5G introduces a new set of frequency bands that will go as high as 6 GHz where data rates can reach one or more Gbits per second. These higher data rates will provide new services that have much faster connectivity, or as Verizon Wireless calls it, enhanced Mobile Broadband.

The last frequency tranche is above 24 GHz where data rates can now reach 10 Gbits per second or higher.

There are three key observations to make here in relation to the battery. 

First, there will be a substantial increase in the amount of data traffic with 5G. Each bit of data consumes a small amount of battery charge. While electronics are getting incrementally more efficient in power usage, this efficiency is no match to the massive increase in data traffic, anticipated to be 1,000X higher than present-day volumes. This, unquestionably, will be the first strain on the battery requirements necessitating higher battery capacities and energy densities.

The second observation is more subtle but potentially more potent. The 5G networks provide new applications that are time and mission critical with a very low latency. In other words, the time that it takes the data to make a round trip from one device to another, and back to the original device (what engineers call latency) will decrease from a present-day value near 100 ms (milliseconds) to less than 10 ms. 

Who cares, you might ask! Imagine two autonomous vehicles on the highway traveling at 65 mph (105 km/h). In 10 ms, the vehicle would have traveled nearly one foot (about 30 cm). In 100 ms, the distance is ten feet or nearly three meters. This is the difference between avoiding a collision or a potentially tragic accident. 

But low latency means that the apps processor (or CPU) will be getting far less idle time that it does today. You see, battery-operated devices rely on the electronics being asleep (not drawing power) for a good portion of the time in order to save battery. So when the processor needs to be awake a longer duration of time, it will have a substantial impact on power consumption, and consequently the battery. 

The third and last observation relates to the new higher frequency bands at 3 – 6 GHz and greater than 24 GHz. Physics tell us that power consumption increases linearly with frequency. So just by going from the 900 MHz band to the 6 GHz band will incur up to 5X increase in power. 

Additionally, waves at these frequencies do not travel very far and tend to be greatly attenuated by physical obstacles like buildings and trees. This limited propagation requires that network carriers (like AT&T and Verizon) install far more antennas more densely. This large capital outlay will most certainly take time. Consequently, handsets operating at higher frequencies will most certainly need to increase the transmission power to overcome the attenuation. Once again, the battery suffers.

Of course, it is fair to expect that the power utilization in 5G networks will improve over time and manufacturers will derive improvements in efficiency. However, it is highly unlikely that 5G power requirements and impact on battery will be similar to those of 4G/LTE. The demands on the battery are certain to increase and put more constraints on battery performance and safety.

24Dec 2017

If Tesla Motors reduced the power of their flagship Tesla electric vehicles after, say, 50,000 miles of driving, the world would be up in arms. If General Motors throttled the Corvette engine to 4 cylinders after some number of miles, the government would probably be investigating. So why is it that when Apple throttles back the processors on their iPhones, we scratch our heads and don’t take Apple to task?

Apple is throttling the processors to preserve battery life. That is a fact admitted by Apple itself. Consumers have complained about premature shutdowns in older iPhones with aged batteries. Understanding the reasons behind such behavior is the topic of this last post of 2017.

I start by explaining a fundamental property of a battery: its voltage curve. The voltage curve is the relationship between the voltage of the battery and the amount  or rather percentage of electrical charge stored within the battery (naturally, 100% means full and zero means empty). You, as a user, get to see the gauge reading of the remaining charge in your battery, but not the voltage. We care about both values (charge and voltage) because either one of them can cause your smartphone to shut down.

So let’s dig a little deeper in the first figure below and understand how charge and voltage are related. It is the voltage curve for a fresh (unused) battery with nothing connected to its terminals. This curve is what engineers call the open-circuit voltage, i.e., no electrical current is flowing. One will notice that as the battery goes from full (far left) to empty (far right), the voltage gradually drops until it reaches a “cliff.” This behavior is characteristic of lithium-ion batteries. You will notice that the voltage is very low when the battery is empty.

 

 

Now let’s examine what happens to this curve when the smartphone electronics are connected to the battery. Engineers call this situation “under load” because the battery is now powering the electronics inside your mobile device, and electrical current flows through the battery. The next figure below shows that, in this scenario, the voltage curve actually shifts down. You will still notice that, however, the general shape of the voltage does not change much. The only change is that the voltage is now a little lower. The larger the current (the load), the larger the shift. A small change in voltage is ok, but as we will discover a little later, a large drop in voltage is not ok.

 

 

I will digress a little here to explain this drop in voltage. For that, we need to recall some high-school physics: Ohm’s law. When electrical current flows through the battery, the actually voltage is reduced by an amount equal to the electrical current multiplied by the battery resistance.

Two key observations to make here based on Ohm’s law:

  • A higher internal battery resistance results in a larger voltage drop;
  • A larger electrical current (to power the smartphone electronics and screen) also results in a larger voltage drop.

This may sound complicated if you don’t remember your high-school physics, but please bear with me. All you need to remember so far is that the battery has an internal resistance. A fresh battery has a small resistance. An old battery has a larger resistance. A faster processor and bigger display mean more current to power the device.

Therefore, as the battery ages, the voltage curve shifts down more and more — precisely what the figure below shows — until something really bad happens. The voltage of the battery is so low that it can no longer operate the electronics of your smartphone especially under peak conditions when the processor or the radio electronics need more power . The red curve below is for an old Apple iPhone 6 battery after 600 charge-discharge cycles. One can see it is now substantially lower than the voltage curve of a fresh battery. This now spells trouble because the low battery voltage may not adequately operate the electronics.

 

 

No we get to the crucial part: how does this relate to Apple’s throttling back their iPhones.

Most smartphone electronics, in particular the radio and wireless components, cannot operate when the voltage drops below 3.3 or 3.4 V. If the battery voltage does drop too low, the smartphone actually shuts down prematurely.

Let’s illustrate that point further in the next chart. The dashed green line is at at 3.35 V (a reasonable intermediate point between 3.3 and 3.4 V). Let’s first focus on the black curve (that of a fresh battery). You will notice that the battery voltage reaches 3.35 V right at empty. That’s good. That’s exactly what we want our smartphone to do. We want it to shut down because there is no more charge left in the battery, which corresponds to the battery gauge reading zero percent.

 

 

But in an old iPhone 6 (red curve), that’s not what happens! Instead, the battery voltage is too low to power the smartphone electronics even when there is remaining charge in the battery.  It shows that an old iPhone 6 battery reaches the low voltage point with the battery still holding about 20% of its charge. That’s not good; it means that this iPhone will actually shut down prematurely while the battery gauge reads about 20%. This is what confuses consumers.

So far, I am hoping I have not lost you in this lengthy explanation, and that you recognize how an older battery loses its voltage, which leads to an early shutdown.

This is, in particular, an acute problem for Apple because Apple rates its iPhone batteries at 500 cycles. In other words, after 500 charge-discharge cycles (or about 1 ½ years), the iPhone battery has degraded sufficiently to exhibit the low-voltage problems described above.

Fortunately, many other smartphone makers choose to use batteries and solutions that extend the cycle life of the battery to 800 or even 1,000 cycles – or at least 2 years worth or more. Sony Xperia smartphones, for example, do provide batteries with cycle life that is substantially more than 500 cycles.

So why does Apple throttle back their old iPhones? When the iPhone processor is running at full speed, it can draw a significant electrical current from the battery. Remember that Ohm’s law is the product of the resistance and the current. So by throttling back the processor, the current draw is less and hence there is less voltage drop because of Ohm’s law. The net effect is avoidance of an early shut down at the expense of user experience! What Apple should do instead is to make sure that their iPhone batteries can deliver 800 or 1,000 cycles instead of 500 cycles. By the way, you will notice that iPad batteries are rated to 1,000 cycles which is why you don’t see old iPads suffering from the iPhone shutdown problem.

If you own an old iPhone and are experiencing a slowdown, please go to the Apple store and get your old battery replaced….or get yourself a new smartphone with a better battery.

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UPDATE: On 28 December 2017, Apple published a letter to its customers offering to replace the batteries in older iPhone models that are out of warranty for $29 instead of the standard $79. Kudos to Apple for taking responsibility for this issue and standing by their customers.

04Oct 2017

Late summer is the season of new smartphones. Apple, Google, Samsung, LG are only a few names that announce their best ever devices in September. By now, you have all heard of or seen the new iPhones including the iPhone X, the beautiful Galaxy Note 8, the highly acclaimed LG V30, and today, the new Google Pixel 2 family. The Internet abounds with device reviews so this post will stay focused on their batteries.

Let’s start by comparing the batteries from this year’s devices to their kins from last year. The capacity figures (the mAh) vary up or down a little. For example the iPhone 8 and 8 Plus lose a few mAh compared to the iPhone 7 and 7 Plus but nothing significant. The Galaxy Note 8 sports a slightly smaller battery. LG adds a little extra capacity to the V30. By and large, it would be fair to say that battery capacities have not changed significantly from 2016 to 2017. Modest improvements in power consumption most likely contributed to maintain the status quo in battery capacity.

The other visible trend is that 6-in devices continue to use capacities in the range of 3,200 to 3,500 mAh, while their smaller 5-in brethren are using batteries with capacities near 2,700 mAh. It is not a surprise that the larger devices show a better battery life lasting one day or even longer. The iPhones 7 and 8 continue to lag with reviews complaining of less-than-standard battery life.

But not all is good news. The third trend is increasing pixel resolution and density. Full HD displays (1080 x 1920 pixels) are giving way to displays with much higher pixel count, pixel density and color experience. The Galaxy Note 8 exhibits the largest pixel count at 1440 x 2960 closely followed by the LG V30 and the Pixel 2XL which was manufactured by LG for Google. These larger and richer displays do consume more power and they will strain the battery’s capability to last all day. It is true that the new OLED displays are somewhat more efficient than LCDs but size and pixel count remain the dominant factors in the power equation. Expect that trend to continue well into 2018 causing the smartphone manufacturers to consider batteries with higher capacities while still maintaining slim designs.

The Galaxy Note 8, the LG V30 and the iPhone X gave us this summer a vignette of the future: Rich edge-to-edge displays with unmatched computational capabilities all embedded in very elegant and thin designs. That spells one thing: The battery challenge will not abate any time soon.

31Aug 2017

We proudly announced today that the new LG flagship smartphone, the LG V30, includes Qnovo’s adaptive charging technology. The V30 uses Qnovo’s QNI solution, our most sophisticated algorithms to manage its lithium-ion battery. In this post, we open our doors to give our readers insight to our technology and QNI in particular.

As complex and exotic as the battery may seem, you, the consumer, care only about a handful of things.

First, will the battery last you a whole day of use, no marketing gimmicks?

Second, will it charge fast enough? You don’t need blink-of-an-eye-charging but you don’t want to wait long too.

Third, will it last you at least two years or more, given that you are paying a premium price?

And lastly, can you rely that it will not risk your safety and the safety of those around you?

These attributes collectively define your overall battery experience; not one of them, but all of them together.

To last you a full day, the battery must have plenty of charge capacity, i.e., a lot of mAh. This is equal to a range between 3,000 to 3,500 mAh for today’s crop of smartphones. Anything more than that will make the smartphone unwieldy or too thick. To fit a 3,000 mAh battery in the small physical space inside a smartphone means high energy density. Today’s state of the art is near 650 Wh/l operating at a maximum voltage of 4.4 V. That’s the first headache already. At this high voltage and high energy density, the battery is really not happy and needs a lot of caring. I mean a lot of caring!

Fast charging the battery amplifies all the concerns of high voltage and high energy density, and makes them a lot worse. And if you have to charge more than once a day, well, this battery will need even more caring.

High energy density, high voltage and fast charging together are the factors that make the battery fail before two years, and risk making your battery unsafe.

Therein lies the challenge. How do we care for the battery ? and why has this required level of care become so much more sophisticated than ever before ?


As the old adage goes, “You can’t fix what you can’t measure.”

This leads to an important and critical new concept for batteries: Measuring what is happening within the battery, all the time, in real time, and then deciding what to do. By “within” I mean the “chemistry” that is taking place inside the battery…the stuff that you don’t see. This is called, in engineering terms, closed-loop feedback. Engineers know it, study it, and use it in countless situations.

Qnovo’s software adapts to your smartphone a measurement technique widely used in battery laboratories. It is called electrochemical impedance spectroscopy (abbreviated as EIS). It helps our scientists understand what happens inside the battery without destroying it. Qnovo’s innovation is in implementing EIS in your smartphone so that it is always monitoring your battery’s internal chemical processes.

We announced earlier this year that the Qualcomm® Snapdragon 835 that powers the LG V30 includes hardware that accelerates Qnovo’s algorithms. Indeed, the additional hardware in the Qualcomm Snapdragon 835 chipset extends the utility of EIS inside the smartphone. The hardware in this new chipset enables measurements and frequencies that were not available in older chipsets. Qnovo’s QNI software takes advantage of this new hardware to gain deeper insight into the battery, again all in real time.

Now we get to the second portion of closed loop: What to do after making a measurement. As it turns out, and we thank science for that, charging the battery is a powerful knob to alter and affect what happens inside the battery. Qnovo’s adaptive charging takes the information from the EIS measurement, and then adjusts the charging current to reduce and mitigate possible harmful reactions detected during previous measurements.

With QNI, this “closed loop” happens a lot faster than its sister software product, QNS. As a result, it is able to detect more potential problems and react appropriately. Throughout a single charge, QNS makes approximately 200 measurements on the battery, whereas QNI makes close to 20,000 measurements.

Over the past years, we have collected a gigantic database of measurements on batteries from the vast majority of battery manufacturers. We have tested large quantities of batteries under diverse and extreme conditions. This knowledge allows Qnovo to train our algorithms to make them more efficient and more accurate especially as battery materials continue to evolve.


The skeptic might ask, “Great, but how does it help me, the end user?”

The most important benefit that the user derives is the health of the battery. You get a healthy battery AND more capacity AND fast charging…in other words, the consumer gets a great battery experience encompassing the attributes mentioned at the beginning of this post.

You, the consumer, do not have to worry whether your usage might hurt the battery. You don’t have to worry about fast charging because it might damage the battery. You don’t have to worry about charging to less than full because it helps the battery’s longevity. None of these should be your concerns and none should keep you thinking about the battery. Qnovo’s adaptive charging takes care of these battery issues in the background, and gives you a healthy battery with the best user experience.

So, if you are in the market for a new smartphone, do consider an LG V30 and do enjoy its battery experience.