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[Music]
[Laughter]
[Music]
the upcoming talk is um done by
Frank he has delivered the first episode
of that yesterday already um yesterday
he focused on the first part of the
title why we are addicted to lithium
today he's going to focus on second part
and how we shake that
habit um Frank is actually working in
the science department of the news magaz
the online news magazine Golem uh in
case you've missed it go see part one as
well it's recorded and now all the best
and enjoy the talk Frank stage is
yours thanks uh and of course there are
lots of Heralds that also uh really help
uh with the talks and I thank cutson
point for being my Herold today
um yes okay uh yesterday I talked about
lithium ion batteries and why we became
addicted to lithium um so what can we do
about it and I already hinted that we
are going to talk about sodium and uh
last year uh one of the big
announcements uh was uh that catl cutle
I used to call them cutle um which is
the Chinese company uh contemporary emx
Technologies uh uh announc that they
will produce sodium ion batteries um and
they will produce them uh starting in
two years they're starting to build up
all the infrastructure all the factories
that they need to actually build these
batteries um uh in terms of the cells uh
that has been developed um as guys like
Elon Musk like to say uh prototypes are
easy production is hard um so production
takes a little bit longer but they will
come and uh what they announced was a
battery that has 160 W hours per
kilogram um was fast charging uh
retained a lot of uh the capacity even
in cold temperatures much more than most
other batteries um they're more heat
resistant and they're also safer than
lithium ion batteries they use no
lithium no Cobalt nickel graphite no
copper and they're much cheaper and a
lot of people um just uh rubbed their
eyes and thought um what is going on is
that can that be true and the point is
yes it is uh it is true and in fact uh
it's not even possible to build such
batteries but it has been done a long
time ago um uh first examples of the
same kind of construction of batteries
uh even though they were worse a little
bit worse than uh was done in the United
States uh funded by the rpai project uh
that's the department of energy uh that
funded the development for $2.9 million
uh not much money um and uh that was
done in 2012 to 2016 and they developed
uh the exact same kind of battery uh
even though it only had uh 20% less uh
capacity was quite stable uh could last
over thousand Cycles many more than
1,000 uh charge cycles so uh very nice
technology indeed um
it's just that well they they then went
on and funded the company called noasis
and tried to sell it and they didn't
find any investors or buyers uh and that
was that uh that uh similar story
happened with theum iron phosphate um
that we talked about in the last uh in
the last talk that was also invented and
uh completely developed in the United
States and nobody really cared um there
also other companies and I listed them
here on the slide
uh like feradon uh which is certainly
one of the biggest uh also and alas alas
has the chance to become one of the
biggest they also develop similar uh
chemistry and so the problem was never
is the technology there the problem was
always is there investment will there be
enough money uh to to actually build
those batteries and uh catl is the
biggest uh producer of batteries
worldwide and uh when they when they
announce uh they will uh build these
batteries uh you can pretty much believe
them they have the money they have the
resources they know how to do that um
also uh the technology is very similar
to how lithium Works uh it's really uh
just the same you have a cathode on uh
the left side and you have an anode on
the right side and when you charge
battery uh the sodium ions go from the
cathode to the anode or stored there in
the hard carbon uh it's hard carbon it's
not graphite we will talk about that
more and uh when you discharge it uh it
goes in the other direction uh and the
ions go back from the anode to the
cathode and the electrons also go back
from the anode to the cathode um and uh
yeah it's just that you can use the
electricity from the electrons that are
flowing through the wires uh for
whatever you want to do um so uh sodium
is worse than lithium it's not the first
choice for building a battery because
it's slightly worse it's three times
heavier than lithium and it's actually
not that bad uh when you look at the
entire thing because a typical battery
weighs about 4 kilog per kilowatt hour
um that's uh maybe not the best possible
battery uh it's slightly less than 4 kog
for uh the newest kinds of batteries but
but uh the lithium inside is about 130 G
and when you if you just replace that by
sodium it would be 300 G heavier it's
not that much and uh also when you use
sodium you don't need
copper um as you have seen on the other
slide both sides are aluminium normally
on the right side with the hard Carbon
on the anode you would need copper
because lithium uh just combines with
aluminium and uh starts to destroy it so
you cannot use aluminum so you use
copper and copper is much heavier and so
you're saving like one or 200 grams of
uh of material by replacing it with
aluminium and uh so the difference is
just natural almost um the big
difference is really the voltage you
lose about 0.3 volts and that's about uh
10% of the voltage and voltage is uh
well it's uh it's almost the same as
energy it's the energy per electron that
is flowing and so you lose 10% of the
energy and that's a that's a much bigger
difference actually um so all in all you
can you really lose from the physical
properties about 20% a bit more than
10% um what has been developed uh from
uh uh from Shar reps and also from catl
is a battery using Prussian Blue as the
cathode and and uh this cathode has iron
uh as its main uh as as the atom that
the sodium has to react with and uh the
rest is carbon and nitrogen in a nice uh
crystalline uh grid uh that just takes
up the takes up the sodium allows it to
react with the iron and be extracted
from it and that works just fine it's
just that the structure is uh fairly
large uh has a large volume and that's
why it has a low density um density is
about 2 G per cubic cm and that's quite
low for uh a cathode material but
otherwise it's quite okay it's almost
the same as lithium iron phosphate it's
just that it takes more space in the
battery
um okay um the other the other point uh
that that people looked at and we
incredulous is well they must be
promising too much um batter is charging
so fast uh it works better in cold how
is that possible and uh the point is uh
with sodium because sodium doesn't react
so easily with all the stuff around it
um uh the sodium ions can flow easier
through the through the electrolyte and
you get higher ionic conductivity in the
same kind of electrolyte and you use the
same kind of kinds of electrolytes uh
and
yeah that's how you can charge them
faster uh also the electrolyte that you
you can use is properly in carbonate and
normally you cannot use a lot of that um
because it would destroy graphite and
you use graphite in the lithium ion
battery as the
anode with sodium graphite doesn't work
um you use graphite because you can put
the uh you can put the lithium ion ions
in the layers of the between the layers
of the graphite but sodium is bigger and
it's too big for graphite and so you
cannot use it and so you can use uh you
can use the uh proper carbonate uh and
uh just benefit from that because it has
much lower melting point um and you can
use it at freezing
temperatures and uh
yeah yeah hard carbon is uh not as
regular um and it has been used for the
last 20 years uh actually in the year
2000 were the first reports of using
hard carbon as sodium anodes and uh this
material is now very reliable has very
long lifetime very long cycle life uh
the performance has been improved over
the last 20 years uh ever further and uh
yeah it's it's not experimental it's
absolutely sure that is going to work uh
nobody really has any problems with
carbon except for um uh some of the
performance issues like uh lower density
it's not it doesn't have the same
density as graphite because um as you
not very ordered uh graphite is neatly
stacked and very well ordered so it has
higher density uh the hard carbon does
not and you also get higher first cycle
losses um this has been impr proved
recently but um it's it's not quite up
to the standards of graphite with
graphite you lose about four or 5% with
hard carbons it's more like 10% or so it
used to be 20% uh and that's a major
reason why the current uh why the
current batteries by from cutle are uh
much better than the sharp R
batteries on the other hand uh you don't
it's it's not graphite so you don't need
the high temperatures that you need to
uh make graphite as a synthesis and you
like to have synthesized artificial
graphite not natural graphite because it
has Better Properties you can control
the the properties um lower temperatures
means it's uh not as energy intensive
it's more environmentally friendly to do
this synthesis and it's also cheaper
um the uh the other Advantage is it's
not neatly stacked uh it's an irregular
structure and because it's an irregular
structure you don't have a hard limit uh
as to how many atoms you can store in
the structure and uh you can actually
get Beyond uh the amount of uh atoms
that you can that you could store in uh
in graphite um it's just uh fairly hard
to reach that and it hasn't quite been
reached uh at least not not reliably um
catl is claiming 50 milliamp hours per
per gram uh and that is very similar to
what graphite what pure graphite would
do another thing that uh a lot of people
uh really get wrong and I mean uh people
like scientists working in battery um in
the industry as well uh they keep saying
well sodium ion batteries are not good
enough for cars um I don't understand
why I I really don't uh a lot of people
talk about that and they never argue
with numbers they just say Well it's
worse than lithium and because it's
worse than lithium it's obviously not
good enough for cause uh and but when
you look at the numbers uh you can say
uh well it's the same numbers as you
would get in a Tesla Model 3 and that's
a car that is sold for over
$40,000 if it's good enough for an car
that cost more than $40,000 um you can
assume that it's probably good enough
for a car um and not just a short range
uh very cheap car but uh cars in general
um uh the volumetric density that I've
uh that I have here is an estimation
because catl didn't publish that figure
but you can make very plausible
assumptions uh how high you can get how
high you can get the volumetric density
my estimate is about 180 W hours per
liter uh if you want details please ask
me in the Q&A uh time is unfortunately
very
short um so yes uh sodium is good enough
for cars uh by the way that good enough
is not a mistake by me uh John good
enough had a hand in developing uh the
Prussian Blu uh he he has still he's
still working at University and has a
research group there and uh in uh I
believe 2011 uh when he was about 90
years old um his group published
research on Prussian flu and that it
could be used for a sodium ion battery
um it's incredible um J good enough is
really uh despite his uh old age uh he's
going to have his H 100th birthday next
year um still very active in the
community and in the uh in development
um yeah okay um sodium ion batteries uh
don't just need uh anodes they also need
cathodes uh the cathode is uh the core
of the battery actually that's where all
the chemistry happens and uh PRI and flu
we talked about this uh it has a uh very
decent performance uh the material
itself if you only had the cath material
is 500 W hours per kilogram in energy
density but it has a low density it's
only 2 gram per cubic centimeter and
that's quite low the problem with that
is uh you need more volume and all the
gaps in the volume uh need to be filled
with electrolyte and uh so you need more
electrolyte and that means it weighs
more and uh so the the ultimate energy
density will be worse than if you had a
material that has a higher uh higher
energy density also the cells take a
little bit more
volume um there's a second uh material
that is very popular uh it's vadium
phosphate uh is great for very high
power uh applications you can uh charge
and discharge at 10 C or 20 C for
thousands of times with that material
but it has a much lower energy density
or somewhat lower energy density um
especially at high power it's it's much
lower um but it works has been developed
by tiat in France uh and actually it
it's originally from the uh from lithium
that been has been adapted to to sodium
uh and then there are layout oxides
layout oxides are the same kinds of
materials that you would have in lithium
ion batteries most lithium ion batteries
um
what is usually used here is mang is
manganese it's not so much nickel based
you can use nickel and sometimes nickel
is used um to improve the the energy
density but um there has been very good
results with almost pure manganes oxide
with just some uh stabilizing other
materials and you can get 600 W hours
per kilogram and some of the best uh
lithium materials uh only reach about
750 so it's about % of what you would
get with uh lithium but there are some
other problems
um um the problem with sodium is uh
because the sodium ions are bigger than
lithium uh the structure is um somewhat
different uh in the materials and you
can choose you can choose between either
having a material that is very stable
and that can reach very high energy uh
densities but uh you have to synthesize
it in a way uh where you only have 2/3
of the sodium uh inside the material and
the rest of the sodium has to come from
the
outside uh and usually when you have a
battery you have all the when you have a
lithium ion battery you have all the
lithium inside the battery inside the
cathode of the battery when you uh when
you build the battery and then you just
charge it and move the move the lithium
over to the anode side uh when you want
to use these sodium poor and very stable
materials then you need to get your
sodium from elsewhere either you al
already have it in the anode side or you
put it into some other material and uh
research has been going on to put it
into all sorts of things uh the binder
that keeps all the all the powder
together uh the
separator that separates the anode and
the cathode um even the the conductive
carbon uh people try to put some sulfur
in the conductive carbon and uh combine
it with sodium so the sodium could be
released uh and so on so there's uh um
there's a lot of development going on
there to to use that the other way is um
you have a sodium Rich structure that is
somewhat more unstable only last for a
few hundred Cycles but what you can do
is you can get a structure that is kind
of in between and uh where you get at
least a bit more than 500 W hours per
kilogram and uh that is um that has been
demonstrated already um and farion which
is in Great Britain uh they have
demonstrated a material like that with
about 500 wat hours per
kilogram um their batteries are also uh
uh very safe um the safety of sodium ion
batteries is in general much better um
than lithium ion batteries um because
the sodium salts um disintegrate at
higher temperature
um the sodium salts are like the first
um the first thing that starting to
disintegrate when you heat up a battery
and uh the problem with that is there's
Florine in these uh in these salts and
the Florine starts to react with the
electrolyte around it and it starts to
get it starts to um increase the
temperature of the battery even a little
bit more and a little bit more and a
little bit more and at some point you
reach the point where the cathode
material itself starts to disinte
and release oxygen or some other
volatile components and the entire thing
starts to heat up and essentially
combust um that's a big problem with the
nmc materials nickel manganese carbonate
for uh NC manganese Cobalt for lithium
ion batteries U which can be very
flammable um it's much less a problem
with other
materials um one of the other Advan ages
is that you can use propol and carbonate
which is liquid at low temperatures um
in uh lithium iron batteries you have to
use aine carbonate which has a much
higher melting point only gets liquid at
around 30° uh so in a very warm summer
day it would be liquid otherwise it's
solid and you need to mix it with other
components that are very volatile that
have uh and uh um yeah turn into gas
very easily and very flammable and and
uh so that's one of the main reasons why
lithium iron batteries uh can turn into
Firebolts very quickly uh and you don't
need those those additives here to
reduce the the melting point because
melting points already very low um yeah
so that's why the flammability is not
quite so
bad um the other point in safy is you
can discharge a battery uh a sodium ion
battery to Z volts because there's no
copper in the current collector um the
copper would normally dissolve into the
electrolyte and then uh next time you
start charging it uh after you fully
discharged it um you would get copper
somewhere in the battery and that
somewhere could be absolutely anywhere
and you can get shortcuts and you can
absolutely destroy the battery like that
that's why lithium iron batteries um
must never be completely discharged uh
it's very dangerous actually uh there's
no problem with that in sodium ion
batteries and that means you can work on
it you can completely uh discharge a
battery and work on it without having it
at 400 or 500 WTS or something like that
and get shocked by that um so everybody
can can work on a fully discharged
battery no problem um very big benefit
in terms of safety
um of course uh energy density is very
important and uh a lot of people think
that sodium ion batteries because
they're not the highest energy density
um will not quite be enough and they
would like to have higher energy density
so there's a there's a possibility and
catl in their presentation already used
this and showed that they are going to
develop this is to Simply use both kinds
of batteries in one car in one battery
pack um so you use both sodium and
lithium I ion battery cells uh so you
can use some cheaper cells the cheaper
sodium ion cells along with the lithium
ion battery cells and uh you can get the
best of both worlds especially when it
comes to the cold temperature
performance uh the sodium ion batteries
can uh you can start driving your car
with the sodium ion battery cars uh
batteries while you heat up the lithium
ion batteries especially with lithium
ion phosphate which is a technology that
is very sensitive to cold temperatures
and when you use both of them together
uh you have a much better battery pack
overall
and uh in terms of energy density uh you
can uh really choose what you want um
depending on and I've done it here with
uh wat hours per kilogram but it works
the same with wat hours per liter
depending on whether you your problem is
uh depending on getting uh uh small
volume or small Mass uh whatever you
want and uh so if you if you choose uh
75% sodium uh you can get a slightly
slight increase in energy density um if
you just want to uh if you just give up
on on 10 W hours per kilogram so you go
from 170 W hours per kilogram to 160 uh
you can save 25% of the lithium in the
battery pack uh it's uh it's uh
absolutely possible to save a lot of
lithium that way and uh especially when
you when the lithium supply is tight uh
this can be very
important um the materials used
especially this is again for the catl
battery um is aluminium iron carbon
nitrogen carbon hydrocarbon uh and some
phosphorus and Florine um and that's it
um those are very common elements and
this is from the Wikipedia article of
the uh crustal abundance of uh elements
and you can find them all here at the
top of the list uh um lithium would be
at Place 33 I think uh along with nickel
um something like that um as you can see
a lot of these elements are very high up
uh also look at Place 12 that is
manganes and manganes is a very popular
choice for the layout oxides in uh
sodium ion batteries in the cathodes
here uh cost can be much cheaper uh
especially because the raw materials are
so cheap uh but it's not just the raw
materials uh the synthesis uh is also
much cheaper because um uh the layout
oxides are Ceramics um and if you know
how to make Ceramics um you know that
you have to fire it at very high
temperatures and uh if you have a cup
like this this ceramic would have to be
heated up at almost 1,00 deg CS um to
make this into a ceramic um but for the
press and blue uh the temperatures you
need is no more than the hot tea that I
have here in the
cup and that I really need now um
the the cost is very low um uh the
material cost is like a dollar or
something like that it's very very
and for the completed material it's just
a few dollar per kilowatt hour in most
batteries the cathode is the most
expensive part of the battery uh in
sodium ion batteries uh it's uh well
it's not the cheapest part but it's
among the cheap parts um so uh the the
manufacturing is much more important so
if you can scale up your your
manufacturing plants to be very big and
very cheap uh then the batteries
themselves can be very cheap and that's
how catl uh wants to achieve like 30 or
$45 per kilowatt hour and that's quite
possible especially because the Sals
that you need and the electrolyte is
much cheaper and you don't need copper
for the foils and because the
electrolyte is much more resistant to
high temperatures you can use higher
temperatures for the drying process
after you have coated the uh after you
have coated the uh foils with uh with
your cathode and your anode material and
then it's wet and you have to dry it out
and you do that in a long ovens and the
higher the temperature can use uh the
shorter time is required and the shorter
and smaller your ovens can
be an important thing that uh strangely
enough was brought up Time and Again by
a lot of people who doubted uh this
development is that yeah we have seen so
many startups uh promising new
technology well catl is not startup uh
it's it's the largest battery
manufacturer in the world I I don't I
don't know how these These are arguments
uh are even started uh it's very strange
they have years of experience uh they
have support by the Chinese government
officially and uh they will not suddenly
start lying about what they can do with
their technology especially because we
know this technology it has been
developed years ago uh we all know it's
possible at least if you if you read uh
in the in the literature and if you
followed uh the old developments um you
will have to get used to the idea that
this is actually going to happen it's
not going to happen on a small scale
it's going to happen on a big scale
because it's the biggest uh battery
manufacturer in the world um so sodium
ion batteries will come and they will
come in two years and you better be
prepared um not like the people who are
surprised by uh lithium iron phosphate
these
days okay two slides um what's next uh
next is the second generation that was
announced uh will be about 200 W hours
per kilog similar to lfp um this is a
similar performance to what feradon is
already
demonstrating uh using L oxides but uh
if you just uh exchange the uh the
farad's uh own anode materials with what
what catl has announced you already get
to 200 wats per kilogram so this is kind
of quite realistic um the big question
is what kind of layered oxide will catl
use and they have said absolutely
nothing on that uh if there's nickel
inside or not uh nickel would be a bit
more expensive uh most materials are
dominated by manganese though so they
should be quite cheap but they are
ceramic so they need higher temperatures
and uh uh processing costs uh quite a
bit more um okay and after that um
because uh I think the uh the rumors are
that catl will announce the second
generation this uh this coming year in
2022 um we will see uh it's certainly
quite realistic the the technology is
not that far away um because layer
oxides have been demonstrated to be uh
possible and uh catl has all the rest of
it um so after that uh what we will
probably see is is anode materials using
prese sodiation um that can achieve uh
higher capacity and also fewer losses in
the first cycle uh first cycle loss are
typically about 10% and if you can uh
just uh reduce these losses by just
putting more more sodium in in the first
place uh that would be great uh and then
you could also use these layered
material these layered oxide materials
uh that don't have enough sodium in the
layout oxides at the beginning and doing
construction of the battery and then you
could reach uh energy densities between
200 and 250 wats per kilogram and uh
that would be very similar to what
lithium ion batteries have now and of
course you can do solid state batteries
with lithium with a lithium um anode uh
just pure pure lithium anodes but you
need different separators you can do the
same with sodium and pure sodium anodes
pure sodium metal and would be much
better you would get much higher energy
density but um with sodium it should
be actually easier to achieve that uh
the problem is it's harder to achieve
that if you don't get money to do it and
right now all the money goes into
lithium ion batteries um so it's from
from practical point of view it's much
harder even though from a physical point
of view it may even be uh easier
um and in in the future we might see
fres and flu batteries with 250 W hours
per kilogram which is granted not that
great it's as good as uh some average
lithium ion batteries these days um but
it could be extremely cheap um
yeah maybe uh that's a bit these two
slides were a bit of speculation okay
thank you and I hand over to the
Q&A
hello okay uh thank you very much for
the nice talk
Frank um there are a couple of question
very short again yeah I realize that um
someone is wondering is the biggest
problem with our sodium batter batteries
um their weight and if so isn't that a
relevant for um uh stationary batteries
such as used in Grid scales yes exactly
um that is in fact one of the reasons
why a lot of people said uh sodium ion
batteries will only be used for um for
station area storage uh and that has
become a bit of a meme actually and uh
because people kept saying okay it's
just for stationary storage and maybe
some light duty Vehicles slow vehicles
um people just kept repeating on kept
repeating that and saying that and
nobody ever looked at the numbers and at
some point you ended up with a situation
where um yeah the numbers are in fact
just as good as the Tesla Model 3 and
people still didn't realize it but kept
repeating the meme that uh that sodium
is not good enough for
cars and yeah um yes of course
stationary storage absolutely Ely um and
uh in a few years people will look at
lithium batteries used for stationary
storage as a bit of a
waste all right thank you um are you
aware of batteries with a lower density
than
water um lower densities than water I
wouldn't know because that's kind of
hard to do um because you always need um
I mean lithium has half the density of
water okay uh but you need to react it
with something and that that something
you want to react it with um that is
kind of hard um you can of course always
build a battery that's much lighter than
water by putting a few battery cells
into a container and make it airtight
and it's uh it has an average density
that is lower than that of water um so
yeah um there are cath materials that uh
are made up of polymers uh but you
cannot uh you don't have any sodium in
those material you can put sodium in and
have the reaction and so on but
um yeah those are polymer polymer
materials uh that are in research uh
might be quite cheap uh but they have
other challenges in using
them thanks uh someone is wondering
where to start when planning to recycle
electronic stuff and trying to bring the
bacterials back to whoever needs it or
is there some kind of a B for
materials uh I'm sorry I didn't quite
get that um what was the the last bit uh
is there some kind of bay for materials
so some place where you could bring
these H okay um right now right now it's
not um uh the problem with recycling of
batteries right now especially lithium
iron batteries in electric cars uh is
simply that they are too good um they
they
just um unless you crash the car the
battery will usually last until uh well
as long as the car is running and most
of the lithium iron batteries and cars
are just working there in the cars some
have been recycled but it's a minority
of the entire of the entire thing so um
uh there are a lot of recycling uh
companies that have been uh that they
didn't quite get into business because
um their business model said that there
would be a lot more uh defective lithium
ion batteries than there actually are
these days and uh they they they want to
recycle them that but they just can't
find enough and uh it will take a bit
more time uh to get Recycling and will
be similar with sodium ion batteries um
as soon as those batteries are actually
available as soon as the waste batteries
are actually available you will get to
see uh some recycling going on of course
thank you and one Galactic life form um
is wondering um and it this is a bit
farfetched but if that lifeform is
remembering correctly there was research
on liquid
batteries um and probably there's a
better term for that um did anything
happen in that
department um I I did read about this
about 10 years ago so uh I'm sure that
something must have happened in that
department but uh nothing that was uh
nothing that ended up being um
commercially relevant uh
or oh I'm I'm just thinking about which
what kind of what kind of battery they
meant um there there are two kinds of
liquid batteries uh one where you had
just two liquids on top of each other
and then just that just formed a battery
and you had to separator in between in
between the two liquids more or less um
that's what I meant the other is of
course Redux flow batteries uh like uh
most popular is vadium Redux flow and
the problem with vadium Redux flow is
that it has a low voltage and that means
you need a lot of vadium to store a
given amount of energy and uh it's just
uh not very competitive in terms of uh
in terms of the price per kilowatt hour
um but there are some other developments
uh also using sodium uh also using other
compounds uh in that direction um
whether or not they will be competitive
uh we have to see um I don't think that
vadium uh vux flow is competitive uh
even though some some demonstration
units have been built but they usually
very small and uh it's it's really just
um because they can get subsidies from
it all right thank you and last question
for this talk uh which batteries are
better suited for B directional
flows um
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well these are actually
quite uh they work in both directions uh
quite well um also at high power um
usually this charge is a bit better than
charging a battery um because when you
charge a battery uh you have to take
care that you don't form uh form pure
metal and get metal dendroides uh that
might penetrate your your separator
especially if you don't have a separate
a separator mat material that is
resistant to the stand rides which uh
normally it's just like a piece of
plastic a porous plastic uh um like a
poly polyethylen like you know like a
shopping bag or something just much much
thinner and uh poral um and that can
easily be penetrated and you don't want
that so you have to be uh you have to
limit your your charging speed uh
especially at low temperatures where
this can happen quite easily um but
other other than that it's uh it's
pretty much uh yeah it's just fine you
can you can use it in both Direction at
very similar uh
Powers thank
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you