Samsung Note 7 Battery Explosions: Is "Fast
Charging" Tech To Blame?
Nobody—not even
Samsung—knows exactly why the Note 7s blew up. These are the leading theories.
The first thing Samsung talked
about during a pre-launch briefing on its Galaxy Note 7 back in
July was the phone’s battery and its new "fast charging" technology.
The subtext was pretty clear: "Our phone has a bigger battery and charges
up faster than the (then-forthcoming) Apple iPhone 7."
This new feature has become one of the main theories on why the
battery in the Note 7 had a tendency to blow up—a malfunction that necessitated
one of the biggest and costliest product recalls in consumer tech history.
Ultimately, the reason Samsung took
the dramatic step to
discontinue the Galaxy Note 7 was that it was unable to pinpoint with certainty
the reason the batteries in the phones were blowing up. As Samsung engineers
struggled to recreate the problem, the pressure grew from regulators and the
media to make a decisive move.
After the first wave of Note 7 explosions were reported, Samsung
thought it knew what the problem was. On September 2, when I asked Samsung for
a technical explanation of the Note 7 battery problem, the company replied:
"An overheating of the battery cell occurred when the
anode-to-cathode came into contact which is a very rare manufacturing process
error."
Samsung thought at the time the problem
was occurring only in batteries made by its SDI subsidiary. So it set about
replacing all the suspect phones with ones containing batteries made by another
supplier, ATL (Amperex Technology Ltd., a subsidiary of TDK). That SDI would
have botched the production of the batteries sounded odd because, as IDC
analyst Will Stofega pointed out, the subsidiary has a long history of making
batteries that work and don't blow up.
On September 23, reports that those phones were also blowing up
began coming in. Today, Samsung has a far less definite-sounding answer to the
question of "why."
"A thorough investigation takes time, and it would be
premature to speculate on outcomes of the investigation," a Samsung
spokesperson said in an email statement Wednesday. "In the U.S., we have
received a small number of reported cases of issues with replacement Note 7
devices. We are working around the clock to analyze the causes of the reported
cases."
The New York Times reported
that many Samsung engineers have been trying to replicate the fault that made
the SDI and ATL batteries explode, but have failed. So on the day the Galaxy
Note 7 became a discontinued product, the cause of its demise remained a big
fat question mark.
Several theories have emerged over the past few weeks about why
both the SDI and ATL batteries overheated. One theory goes that it was the
design of the battery, not the "manufacturing process" (as Samsung
originally said), that caused the problem. The battery design could have been
completed by Samsung engineers then fed to SDI and ATL to manufacture according
to spec.
A Korean government regulator concluded that the positive and
negative charged plates inside the batteries were too close to one another at
the rounded edges of the phone. When positive and negative poles in a lithium
ion battery physically touch, a very rapid and violent chemical reaction takes
place. The regulator also pointed to defective coating material on the negative
electrode.
The reason these findings are interesting is because they suggest
that the phone’s overall design may be affecting the safety of the battery. The
plates being too close together may have resulted from the intense competitive
pressure to produce ever thinner phones. And not just thinner phones, but
phones that also contain more components. The Note 7, for instance, had a new
iris scanner on board, and also retained the analog headphone jack, which takes
up a lot of space. The regulator also pointed to the battery design within the
phone’s rounded edges—another new design trait in the Note 7.
There’s also an intense market demand for phones that charge
faster, and it’s Samsung’s attempt to meet this demand that may be the most
compelling explanation for the explosions. Samsung said its new fast-charging
technology lets the battery in the Note 7 charge to 50% capacity in 30 minutes,
a claim born out in my tests.
Here’s how fast charging works: USB chargers with fast-charging
circuitry built in can send a higher power output into the smartphone. Any
charger with an output of greater than 10 watts is considered "fast
charging." The Note 7 uses a USB-C charger with fast-charging tech inside.
Specialized power management chips inside the phone moderate the power level it
can handle without overheating the phone or overcharging the battery.
When battery manufacturers say
"vent with flame," they mean "explode."
Qualcomm supplies its 820
Snapdragon processor and various power management chips for one of the two
versions of the Note 7. The company points out, however, that those chips
aren’t involved in the regulation of the power flowing into the battery during
charging. "Qualcomm does not provide any of the battery charging
electronics commonly used in both versions of the Note 7," a Qualcomm
spokesperson said in an email to Fast Company.
Qualcomm also points out that the power management chips it
supplies for the Note 7 are also used in other mass market phones (Samsung's
Galaxy S7 and S7 Edge, Xiaomi's Mi Max, and ZTE's Nubia Z9 Max) that don’t blow
up. Qualcomm's own QuickCharge technology was indeed used in one version of the
Note 7, but only for its protocols used in communication between the various
power management chips in the device.
Lithium-ion batteries in phones contain three major physical
structures: a positive electrode made of Lithium cobalt oxide, a negative
electrode made of carbon, and a separator layer made of micro-perforated
plastic. The layers are submerged in an organic solvent substance. During
charging, lithium ions move through the plastic barrier layer from the positive
lithium electrode and attach to the negative carbon electrode. As the battery
is used (discharged) the opposite happens: Lithium ions move back over to the
positive electrode.
Lithium-ion batteries can become unstable if charged at a
higher-than-specified voltage rate. The cathode material can become an
oxidizing agent, losing its stability and producing carbon dioxide. If pressure
within the cell continues to rise, a safety interrupt is supposed to kick in.
If such an interrupt doesn’t happen (for whatever reason), pressure within the
cell can continue to rise and the safety membrane around the cell can burst,
causing the cell to "vent with flame." When battery manufacturers say
"vent with flame," they mean "explode."
"It casts a pall over the
whole fast-charging technology; you have to be concerned," says Steve
Rizzone, CEO of the long-range wireless charging tech supplier Energous. "The whole
idea of rapid charging is going to have a negative connotation to it."
Rizzone says that problem points to the need for a new way of charging devices.
While the technology has yet to be productized, Rizzone believes the constant
over-the-air charging Energous is building will let users constantly be
"topping off" the charge in their phone’s battery, which would
lighten the load on the battery.
So the Note 7 debacle, whatever the exact cause, may have been the
result of a smartphone maker trying to respond to the marketplace and simply
asking too much of the battery technology we have today. "What you’re
seeing is proving more and more that powering larger batteries, and charging
those batteries quicker, the battery chemistry can’t keep up with those
requirements," Rizzone says.
Lithium-ion batteries are far more reliable and safer than earlier
battery technologies, but there are limits to the amount of miniaturization,
power capacity, and rate of charging phone makers can impose on them.
Maybe it was inevitable. Maybe Samsung was just unfortunate enough
to be the first phone maker to (loudly and violently) run smack into the wall,
the outer limits of what lithium-ion technology can safely be asked to do.
MARK SULLIVAN
https://www.fastcompany.com/3064639/analyzed/samsung-note-7-battery-explosions-is-fast-charging-tech-to-blame
No comments:
Post a Comment