Well, it's been several months since Samsung's nuclear Note 7
fiasco, but we now, finally have the exact cause for why...
the note 7 batteries were catching fire.
Thanks to a massive investigation by Samsung, themselves.
So I thought I would make this video to explain exactly...
...what happened, in a way that is easy to understand for basically anyone
And it is pretty interesting, because as you might know, they recalled the phone...
and made new ones with totally different batteries from a different manufacturer and they still were catching fire.
It turns out that both sets of batteries had their own seperate issues.
So that's what I wanted to explain in this video.
Let's find out what went wrong.
So the first thing I want to do is quickly go over the basics of how batteries in phones are structured
and I'll try to make it pretty interesting, not too boring.
Now, really every battery no matter what kind requires at least 2 components.
An anode which holds the negative(-) charge and the cathode which holds the positive charge
And then there are electrons and ions there which are charged...
at different parts of the battery which actually hold the energy.
Now, I'm not gonna explain the chemistry or anything behind this...
but the important thing to know is that the electrons and charged ions want to get from one side to the other
...and this gives them a lot of potential energy.
When they are allowed to move...
they release this energy which can power the device.
And there's also gonna be some sort of seperator between the anode and the cathode.
which is semi-permeable
and it's gonna prevent the charge from, just transferring instantly
which would be a short circuit.
So this allows you to control how much energy is being used by the phone when it needs it.
Then, when you go to charge the phone, for example
You're basically using external energy from your wall to get the charge...
back on the original side so they have potential energy again.
Now, batteries obviously come in all sorts of shapes and sizes depending on how you arrange the anode and the cathode.
They come in a bunch of different shapes.
Looking specifically at lithium-ion batteries...
...for the Note 7
They used what is known as a "Jelly Roll" design.
It's kind of a funny name.
This is where the anode and the cathode and the seperator...
are layered in, basically, one long strip...
and then it's rolled up
and depending on the shape of the battery like the cylindrical batteries you might typically see...
it kinda looks like jelly roll and that's where it gets its name.
In this case, though, the battery is kind of like a flat and jelly roll.
So even though the battery is flat, the layers inside are still rolled around each other, which is important to understand for the thing next.
To get a better idea of how this looks, this is a side-view diagram,
looking at the flat side of the battery.
and, here is a top-view.
So, in the side view you can see that there are cross sections of the layers
and that's how they're arranged.
So, now that we know how the batteries are designed and structured
We're ready to understand exactly what happened and what went wrong.
So in the first battery, the battery housing was misshapen.
And the corners were basically too rounded off.
And this basically crushed the top layers against each other
which in some cases could cause the anode and the cathode to touch each other directly
which would result in a short circuit
The second battery, however, the one they put in after the recall, had a totally different problem though.
The cathode sheet in that one, which is typically metal, apparently had large "Burr"s.
from the manufacturing process.
A burr is basically a protrusion or deformity from welding or cutting metal.
In this case it was called welding burrs
so i guess it was from welding.
but, anyway, these burrs stuck out enough on the sheet
so it actually penetrated the seperating layer between the anode and cathode causing direct contact between them.
again, causing a short circuit.
Also in the second battery, they apparently forgot to include insulation tape in many of them
making it even more likely for this to happen.
So in both batteries there was different problems which had the same result, a short circuit.
But, what exactly happens when there is a short circuit
and how does that make the battery catch on fire?
Well, think of what happens when you're using your phone to run a game
or some other intensive app that uses a lot of CPU power
your phone probably heats up.
And part of that, of course, is from the processor
but the battery also heats up.
And this is because when it's releasing energy, it's not 100% efficient
so some of it is released as heat
some of that energy is not electrical, but rather heat.