Electronics & systems

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.

_____________________

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.

16Aug 2017

School started this week for most of us so it is time to resume the posts. Today’s post continues with insight into the subtleties of the lithium-ion battery. It is surprising how a simple device, with only two contacts, can be so intriguing and complex.

As summer nears to an end, several smartphone makers ready their newest and greatest devices for launch. Samsung announces their Note 8 on 23 August. LG is announcing their flagship V30 a week later. And we are not forgetting Apple as they ready their newest iPhones in September.

All of these new devices will come with amazingly beautiful and large displays, top-of-the-line processors and of course, batteries to power them. At an expected price point in excess of $700, consumers are keeping their smartphones for two or even three years. So will their batteries last that long?

We will examine here one of the parameters that impact the longevity of the battery…and give you some tidbits on what you can do to keep your battery fresh for longer than average. Today’s post is on voltage. Voltage is the alt-nature to state-of-charge (SOC). This is very much the principle of operation of the fuel gauge — how you get to read at the top of your screen the percentage of remaining battery life.

When I say voltage, I mean the maximum voltage that the battery will see. It also determines the maximum available capacity in mAh. Look at the label of a battery and you will observe a maximum voltage during charge and maximum capacity for that battery. Most state-of-the-art batteries operate at a maximum voltage around 4.35 V or 4.4 V. This is also the voltage that corresponds to a 100% battery reading.

If you choose to charge your smartphone to a lesser percentage, say to only 90%, then the battery voltage stops at a lower value. For a battery that is rated 4.35 V, 100% corresponds to 4.35 V. At 95%, the voltage is 4.30 V. And at 90%, the voltage is 4.25 V. These are small differences in voltage values, but significant differences in capacity.

Let’s take a particular example with a battery having a maximum capacity of 3,100 mAh at 4.35 V. Therefore, at 4.25 V, the maximum available capacity becomes a little over 2,800 mAh.

You are now wondering: why would anyone want to do that?

The answer is: Battery longevity. If you don’t have the best battery, or your smartphone manufacturer is not putting the best battery management intelligence on your device, then you ought to be very concerned whether your battery will last you more than one year. Battery issues after 6 months or one year are a significant cause for warranty returns.

Let’s back it up with some measured data.

The following chart shows the maximum available capacity for a battery rated at 3,100 mAh at 4.35 V. At this voltage, this battery will only last about 400 cycles, or about a year. You will complain about the loss of use much before that.  The brown line shows that your battery has lost 250 mAh of capacity after 6 months….that’s about 2 hours of use time. Ouch!

 

Now, let’s look at the case where the smartphone is charged to only 95%. That is a maximum available capacity of 3,000 mAh instead of 3,100 mAh. Now follow the dark green curve in the chart. It fades at a much slower rate than the brown line. In fact, it crosses over the brown line at about 300 cycles, or about 10 months. In other words, after 10 months, it offers more capacity. This illustrates the tradeoff between voltage and longevity.

A smartphone maker who has implemented advanced intelligence on their battery (like Qnovo’s) will not suffer from this ailment. But if you suspect that your device does not have such intelligence, then you will do yourself a big favor by charging your battery to a maximum of 95% or even lower if you can.

02Sep 2016

The images of melted Samsung Note 7 smartphones are all over the internet. News of Samsung’s massive recall are headline news. It is embarrassing to Samsung Mobile, its marketing and engineering teams, and most certainly its executives. Consumers are wondering how could Samsung ship units with defective batteries that can catch fire.

It is easy but not right to pick on Samsung or be critical of the company at this moment. Why? because this could happen to anyone…that’s right, anyone. If you are an OEM of smartphone devices or consumer devices with lithium-ion batteries, this is the time for you to pay attention to your products because you could be next.

While this sounds ominous, the intent here is to raise safety awareness in the entire ecosystem that depends on batteries. Samsung happened to be the first unlucky company to exhibit the strains that have been accumulating now for several years. I have covered in several past posts how the battery industry has been hitting the wall. Battery materials are reaching their limits. Battery economics are not favorable. Yet, the performance demands on batteries continue to rise. All of these factors are and continue to be precursors to the situation that Samsung finds itself in.

As is often the case in life, we tend to remain complacent until a crisis hits. The crisis is here, and now. Samsung is first to feel the pain, but each and every company in this ecosystem, from consumer devices to energy storage and electric vehicles, should acknowledge the severity of the situation and participate in its solution. Again, why?

This perfect storm has been brewing for a while, in particular, the drive to increase energy density along with faster charging while making less expensive batteries. Increased energy density and faster charging operate the battery near its physical limits. In other words, the margins for error at these elevated performance levels are really thin. For example, the newest lithium-ion cells now operate at a terminal voltage of 4.4 Volts, up from 4.2 Volts a few years back. This increase in voltage is one of the underlying physical tenants of increased energy density, yet it moves the battery every so close to the edge of the safety abyss. Another example relates to charging speed: it is widely accepted now that charge rates are approaching if not exceeding 1C. Electric vehicle makers are actively exploring very fast charging for EVs. Tesla is deploying their superchargers at a fast pace. These superchargers can charge a Tesla model at up to 1.5C, i.e., put in half a tank in about 20 minutes. Fast charging wreaks havoc inside the cell if not properly managed.

So now add the push for making less expensive batteries. Battery manufacturing, unlike semiconductors, does not scale. There is no equivalent of Moore’s law. In other words, as energy density increases, the cost per Wh (per energy unit) does not decrease…au contraire, it tends to increase because manufacturing tolerances get tighter. As a result, capital expenditures go up. Combine that with low-cost, low-quality batteries coming out of China and at a fundamental level, you can see how the financials of battery companies do not look pretty. This invariably leads to changes in manufacturing processes as companies seek more efficient ways to manufacture. But when the design margin of error is so thin, it does not take much before small variations in manufacturing lead to disastrous consequences. Remember, all it took in the case of Samsung was 35 failing devices out of a total of 2,500,000 shipped to cause a recall. This is a failure rate of 14 ppm (parts per million). It is a small number but, clearly, not small enough.

This is not to say that battery manufacturing and battery technology are doomed. There are countless examples in history where engineers built far more complex systems and structures safely and economically…but usually these include a change in paradigm. For example, pause for a second and compare the first commercial airplanes with the most recent jetliners. The newest Boeing and Airbus commercial airliners are marvels in computation and software. Fly-by-wire and automated systems with redundancy are the norm today, yet these new airplanes are scantily faster than their predecessors. In other words, the industry added so much more intelligence and shifted the burden to computation. The result is that modern planes are vastly safer than ever and far more economical to operate.

This is precisely the opportunity in front of the battery manufacturers and their customers, the OEMs, to think deep and hard on how they are going to implement a lot more intelligence to manage their batteries. Kudos to Sony for recognizing this….the batteries in their smartphones carry a great deal of intelligence, perform incredibly well and are safe. I am biased here…a lot of that intelligence is from Qnovo, but that should not diminish from the importance of the point of needing intelligence to manage the vanishing margins of error that battery designers have to cope with.

19Jul 2016

This post includes contributions from Robert Nalesnik. I discussed in the past how fast charging requires two components: i) power delivery – that means getting extra electrical power from the wall socket to the battery and ii) battery management – that means making sure you don’t destroy the battery’s lifespan with all the extra power.

How much more power do you need? Quite a bit more if you want to charge considerably faster. It’s like your car engine: if you want to go faster then you will consume more gas. For a typical smartphone, power levels go up from the conventional 5 Watts to 15 or even close to 20 Watts in some cases.

Delivering higher levels of power is a very active area. Qualcomm has Quick Charge, Mediatek has Pump Express, and there is the USB Power Delivery standard with support from Intel, and the Chinese manufacturer Oppo has VOOC. Not surprisingly, with so many parties trying to influence or even define the standards of power delivery, there is plenty of confusion to go around.

First, let’s refresh some basic high-school science:     Electrical power = current x voltage.

So if we want to deliver more power, we can either increase the current, the voltage or both. Increasing current is relatively easy but more current means a lot more heat…that is until something begins to melt. Not good! That usually puts an upper limit somewhere between 3 and 5 A on the charging current.

The other approach is to increase voltage, from the conventional 5 V up to 9 V, or even 12 V, and in some limited cases even more.

High current charging

High-current charging leverages the fact that modern single-cell lithium ion batteries can be charged using an inexpensive 5 V AC adapter that can be manufactured for about one dollar.

Increasing the charging current is limited by i) the maximum current rating of the USB cable between the AC adapter and the mobile device, as well as of the tiny connector in your device where the USB cable plugs in; ii) cost and iii) heat and safety.

Let’s do some math. A typical USB cable assembly can support a maximum current of 1.8 A. So 5 x 1.8 = 9 Watts max. That’s fine for standard charging but not sufficient for fast charging a smartphone. The new USB type-C cables (with symmetrical connectors that can be used in any orientation you like) can support up to 3 A, in other words, a maximum of 15 Watts. Much better! Under some very limited cases and using special cables, one can push USB type-C to 5 A, or 25 Watts. But at 5 A cost begins to skyrocket, so instead, we see designs gravitating towards 3 A, or equivalently 15 Watts.

To put this in perspective, 15 Watts can charge your typical 3,000 mAh battery at a rate of 1 C, meaning you will get 50% of your battery charge in 30 minutes, and a full charge in  over an hour.

A quick word on heat: if you remember Ohm’s law from your high-school physics, heat increases as the square of the current. That means as the charging current increases from 1.8 A to 3 A, or 1.66X, heat inside your device will increase as 1.66 x 1.66 = 2.8X. Ouch! That’s a lot of heat to remove from the device….and a great topic for a future post.

Power1

High voltage charging

Let’s pause for a moment and think about the high-voltage transmission lines that we frequently see from highways outside of urban areas. Electric utility companies transport electrical power from power-generating stations (e.g., dams) that can be hundreds of miles from a city. If they use the 120 V that you get at your outlet, then the overhead transmission lines will have to carry millions of amperes…this is not only physically impossible, but also economically just prohibitive. So the transmission lines run at a much higher voltage, anywhere up to 800,000 volts. These transmission lines naturally don’t come straight to your house. Instead, they terminate into smaller substations (hidden off main roads near your neighborhood) where the voltage is then gradually “stepped down.”

That’s the same concept used in mobile devices. The voltage from the AC adapter is now raised above 5 V. But what voltage should it be? 9 V, 12 V? more? This is decided by a “handshake” protocol between a specialized chip (usually the power management IC, also known as PMIC) inside your smartphone and the AC adapter when the USB cable is plugged in. This is the approach taken with Qualcomm’s Quick Charge and the USB Power Delivery standard, each using a different signaling mechanism. There is a saying among power supply engineers that “voltage is cheaper than current”, and indeed lower cost components and cables are a primary benefit of high voltage charging.

The USB Power Delivery (USB PD) standard allows voltages of 5, 9, 15 and 20 V and currents up to 3 A. This gives power levels of 15, 27, 45 and 60 W, respectively. Additionally, currents up to 5 A are allowed at 20V, enabling up to 100W. Qualcomm has similar predefined power levels at 5, 9, 12, and 20 V. High-voltage charging has a clear advantage of attaining power levels above 25 W, which makes it the preferred choice for laptops, ultrabooks and 2 in 1s tablets.

power2

How will this abundance of approaches settle out in the market? From a historical perspective, Qualcomm was early to see an opportunity to define high voltage charging in a simpler and cheaper way than the USB committee. They launched Quick Charge 2.0 in 2013 and followed up with the latest 3.0 version in 2015. Qualcomm has been quite successful establishing Quick Charge as a defacto charging standard for smartphones. More recently, Intel and others are successfully driving USB PD and the Type-C connector into PC markets and Type-C is well on its way to become the standard connector across all classes of mobile devices.

In smartphones, the next few years will likely still see multiple power delivery approaches, with chipset and adapter vendors evolving to multi-standard support to bridge compatibility gaps – meaning a smartphone can support multiple protocols such Qualcomm, USB PD, Pump Express…etc. From a Qnovo perspective, we are agnostic and complementary to whatever power delivery approach our customers choose. The higher power makes greater the need for the second component of fast charging: battery management.