you're probably aware that any electric
battery has at least two terminals
by means of two contacts or wires
batteries provide a pathway for the
electrons to travel and thus deliver
power to the circuit and whether we had
to run an electric motor or light a bulb
all we need to do is attach the load to
the battery output pins with the help of
at least two wires
this simple two-wire rule naturally
works for all electric appliances
including home electronics
cigarette lighter adapters and also cell
phones
in fact mobiles use regular dc batteries
that you can use to power any load
provided it has the matching voltage
rating
in most cases the positive and negative
terminals
are on the sides of the battery
connector
however if we look closely at any
smartphone battery we will notice that
there is an extra third connective pad
in the middle and some batteries like
this one have more than three
what is the purpose of these extra pins
let us conduct a simple experiment
we are going to use two jump wires to
feed dc current to this mobile phone
from its original battery
gotta take note of connector polarity
as you may guess we will not be
connecting the middle pin at this time
voila
[Music]
as you can see the phone attempted to
start
but then shut itself down
just to make sure
the phone is working if the battery is
inserted the regular way
so what just happened there
there's a whole conspiracy spreading
online about the battery's third
terminal
most people are positive there is some
kind of sophisticated circuitry inside
the battery that allows the phone to
recognize it and also ensures the
consumer buys only original batteries
thus protecting the interests of the
manufacturer
but is it really the case
let me show you something
i will put my multimeter into resistance
mode
and
the circuit between the negative battery
terminal and the mysterious middle pin
measures 8.5 kilos
[Music]
as we can see now the resistance dropped
to 8.1 kilos
[Music]
and now down to 7.7 kilos
hold on
i'll show you something else
this battery comes from the freezer
and the resistance is
15 kilometers
what we have just observed is the change
of resistance resulting from a change of
battery temperature
resistance is probably the most basic
concept in electronics and a resistor is
the simplest and cheapest electronic
component
i believe now you can guess what's going
on here
the third terminal is the output of the
temperature sensor a thermistor which is
a special type of resistor whose
resistance is strongly dependent on
temperature and it is mounted inside the
battery
and it's quite easy to fool the phone
into thinking that it's actually
connected to a real battery by attaching
a regular resistor between the ground
and the middle pin
in fact using this method you can even
run your mobile from an external power
supply without a battery
so
what is the purpose of this temperature
sensor
the thing is lithium ion batteries used
in all modern appliances including
electric cars are actually dangerous
they can catch fire and explode
but that only happens if the battery
overheats
overheating can occur in two cases
if the battery is overloaded or shorted
or during the charging process
since lithium ion is the best battery
technology available to the day
engineers have taken all precautions to
make sure they can be used safely
original batteries always have a
temperature sensor and also a short
circuit protection board that cuts power
in case of over current
most mobile batteries will shut off if
current goes above 5 amperes
unfortunately chinese manufacturers
often ignore this rule as you can see
this battery does not react to change of
temperature the reason is simple its
logic board has a regular resistor
instead of a temperature sensor
and this one does not react to over
current
which in fact is much worse since it
actually can catch fire if you short it
many online marketplaces sell batteries
that have no protection the reason this
danger is so overlooked and they are so
widespread is because short circuit
rarely occurs in real life
several conditions must match for this
to actually happen
but after watching this video i would
never buy a third-party battery at least
if i were you
that's all for today folks this was ron
martino if you like this video please
comment share and subscribe and i will
see you later