Battery charger fundamentals: Watts, Volts, Amps
Summary
TLDRIn this video, the presenter discusses the need for a more powerful battery charger due to the limitations of their current 650-watt charger, which struggles to efficiently charge high-capacity batteries at their maximum potential. They introduce the fundamentals of battery charger specifications, using analogies to explain the relationship between watts, volts, and amps. The video aims to educate viewers on how to choose a charger that can handle higher power demands for faster charging, while also touching on the importance of efficiency and heat dissipation in electrical systems.
Takeaways
- 🔋 The speaker is considering a new battery charger due to the limitations of their current 650 watt charger which doesn't charge quickly enough.
- 🔌 Understanding the relationship between Watts, Volts, and Amps is crucial for selecting the right battery charger.
- 💧 The analogy of water pressure and flow is used to explain the concepts of Volts and Amps, with high pressure corresponding to high voltage and high flow to high amperage.
- 🔩 The script uses the example of a water jet cutter for high voltage, low amperage and a drainage culvert for low voltage, high amperage scenarios.
- 🛠 Watts represent the capability of electricity to do work, while amps contribute to heat generation, which is important in electrical systems.
- ⚡ Higher voltage systems can output the same amount of power with less current, resulting in less heat dissipation, which is beneficial for safety and efficiency.
- 🔌 The script explains that in electrical systems, especially in countries with different voltage standards, the balance between volts and amps affects the heat generated and the thickness of wires needed.
- 🔄 Battery chargers are essentially voltage converters with an input and output voltage, and the efficiency of these chargers is a key factor in their performance.
- 📉 The efficiency of a battery charger can vary based on the output current and input voltage, and it's essential to check the datasheet for specific details.
- 🚫 The script warns against the use of linear regulators for large input voltage differences due to significant heat generation and inefficiency.
- 📈 The video script promises a follow-up video with a detailed rundown of battery chargers the speaker has been considering, indicating a series of informative content to come.
Q & A
What is the main issue the speaker is facing with their current 650-watt charger?
-The speaker's current 650-watt charger is not able to charge their 1,300mAh 4s batteries quickly enough, barely reaching half the C-rate, even though the batteries can charge at 1C and potentially even 2 or 3C.
What is the purpose of the speaker making a video about their charger dilemma?
-The speaker makes a video to share their thoughts and considerations about getting a more powerful charger, as they have found that their audience appreciates such content, as evidenced by their previous video about a flight control board.
What is the fundamental relationship that the speaker explains is essential to understand for battery charger specifications?
-The fundamental relationship is Watts equals Volts times Amps (W = V x A), which is essential for understanding the power capacity and performance of a battery charger.
How does the speaker suggest thinking about Volts and Amps in terms of an analogy?
-The speaker suggests thinking of Volts as water pressure and Amps as water flow rate, using the analogy of a high-pressure water jet cutter and a drainage culvert to illustrate high voltage-low amperage and low voltage-high amperage scenarios, respectively.
What does the speaker mean by 'Watts do work, Amps make heat'?
-The speaker is explaining that Watts measure the capability of electricity to do work, while Amps are related to the amount of heat generated in a circuit, which is a function of the current (amps) and resistance in the circuit.
Why might someone choose a higher voltage system for their electrical needs?
-A higher voltage system can provide the same amount of power (Watts) with lower amperage, which results in less heat dissipation and can be safer and more efficient for certain applications.
What is the significance of the equation 'Watts in equals Watts out times efficiency' in the context of battery chargers?
-This equation highlights that the power input to a battery charger must equal the power output, adjusted by the charger's efficiency. It's crucial for understanding the maximum charging capacity and the heat dissipation of the charger.
Why does the speaker mention that higher input voltage for a battery charger can be beneficial?
-A higher input voltage for a battery charger means that for a fixed output, the charger will draw less current, resulting in less heat dissipation and potentially higher efficiency.
What is the difference between a switched mode regulator and a linear regulator in terms of heat dissipation?
-A switched mode regulator is more efficient and dissipates less heat compared to a linear regulator, which drops voltage by converting power to heat, thus dissipating more heat as the difference between input and output voltage increases.
What advice does the speaker give regarding the use of linear regulators?
-The speaker advises that linear regulators should be used in the right place and cautions against using them when there is a large input voltage and a low output voltage, as this would result in a lot of wasted power as heat.
Outlines
🔋 Exploring Battery Charger Upgrades and Fundamentals
The speaker discusses their dissatisfaction with their current 650-watt charger's slow charging speed, particularly when parallel charging multiple high-capacity batteries. They introduce the topic of seeking a more powerful charger and plan to share an introduction to battery charger specifications and fundamentals in a follow-up video. The importance of understanding the relationship between watts, volts, and amps in the context of battery charging is emphasized, using the analogy of water pressure and flow to explain these concepts. The speaker also touches on the concept of watts as a measure of electrical work and the role of amps in heat generation, highlighting the differences in electrical systems between countries with varying voltage standards.
🔌 Understanding Electrical Power and Heat Dissipation
This paragraph delves deeper into the relationship between electrical power, voltage, current, and heat dissipation. The speaker explains how higher voltage systems can deliver the same power with less current, thereby reducing heat generation, which is a critical factor in electrical safety and efficiency. They contrast this with the workings of linear regulators, which dissipate more heat as the difference between input and output voltage increases. The importance of understanding these principles when selecting battery chargers is highlighted, as it affects the speed and safety of battery charging. The speaker also mentions the efficiency of voltage regulators and how it varies with input voltage and output current, advising viewers to consult datasheets for precise information.
📈 Summarizing Voltage, Current, and Efficiency in Battery Chargers
The speaker summarizes the key points about battery chargers being essentially voltage converters with an input and output voltage, and how the efficiency of these chargers is crucial for understanding their power capabilities. They explain the basic equation that input power equals output power times efficiency, and how this impacts the charger's ability to deliver power to batteries. The paragraph concludes with a teaser for the next video, which will likely include a detailed analysis or spreadsheet on battery charger specifications, leaving the audience informed but eager for more detailed content in the subsequent video.
Mindmap
Keywords
💡Battery Charger
💡Parallel Charging
💡Wattage
💡Voltage
💡Amperage
💡Efficiency
💡Heat Dissipation
💡Switched Mode Regulator
💡Linear Regulator
💡Power Rating
💡C-Rating
Highlights
The speaker is considering upgrading from their current 650-watt charger due to its slow charging speed.
Parallel charging is being used but it doesn't meet the full charging potential of the batteries.
Introduction to battery charger specifications and fundamentals is provided.
The relationship between Watts, Volts, and Amps is explained using hydraulics as an analogy.
High voltage with low amperage is compared to a high-pressure water jet, while low voltage with high amperage is likened to a drainage culvert.
Watts are defined as the capability of electricity to do work, while Amps contribute to heat generation.
The importance of understanding the balance between voltage and amperage for efficient power transfer is discussed.
The concept that higher voltages can reduce the current and thus the heat generated for the same amount of work is introduced.
The speaker explains the difference between switched mode and linear regulators in terms of heat dissipation and efficiency.
Battery chargers are described as voltage converters with an input and output voltage, emphasizing the importance of efficiency.
The relationship 'Watts in equals Watts out times efficiency' is highlighted as a key concept for understanding battery chargers.
The impact of input voltage on the amount of current drawn and heat dissipation is explained.
The speaker mentions the typical input voltage range for battery chargers and how it affects their output power.
The video will continue in a follow-up to explore specific battery chargers and their specifications.
A spreadsheet with detailed information on battery chargers will be featured in the next video.
The video concludes with a teaser for the next part, emphasizing the value of the information covered.
Transcripts
I've been shopping for a new battery
charger I have the venerable aqui sell
650 watt charger and and I like it and
as you know from the video I posted some
time ago I do parallel charging with it
and it gets it does everything I need it
to do but it doesn't do it very quickly
I can if I have four of my 1,300 million
of our 4s batteries charging on it it
can like barely hit a half C which those
batteries can easily charge at 1 C and
maybe even 2 or 3 C if you really wanted
to push it but it just cannot push the
power to get that done and that's a
little I don't know that's a little
annoying so I've been thinking about
getting a more powerful charger and as
as usual whenever I'm thinking about
something I make a video about it and I
tell you about it because Novus people
seem to like when I do that so I'm going
to take you through a little bit of an
introduction to battery charger specs
and and fundamentals and then I'm going
to do a second video where I'm going to
do a little rundown of some battery
chargers that I've been looking at and
you know people liked when I did that
with the flight control board so maybe
you'll like when I do that with battery
chargers let's get into it
if you're going to understand the specs
for a battery charger you must
understand the relationship that I'm
showing on this slide Watts equals volts
times amps okay if you don't have an
intuitive grasp of what those things
mean then think I find that that fluid
like hydraulics or plumbing is a very
intuitive way of thinking about
electricity as long as you don't go too
far into the analogy and end up saying
something incorrect but people have an
intuitive understanding of how fluid
works because we've all put our thumb
over the end of a garden hose and made
it squirt out right we've all we've all
experienced plumbing all of our lives we
know that water flows downhill and all
these things right so if you want to
think of volts as water pressure and
hams as water flow rate that would not
be an inaccurate way of thinking about
those things so here in the lower left
I've got this is a cutting jet a water
jet cutting tool it has an incredibly
high pressure jet of water shooting out
of it and it's cutting a piece of steel
no kidding
if you weren't aware that this existed
go look it up it is super cool and it is
it is a very high pressure but not a
very high flow rate very little water is
actually coming out it's just coming out
at a very very high pressure and that is
an example of maybe a high voltage low
amperage scenario on the flip side I
have here a drainage culvert and that's
an example of a high flow rate at low
pressure okay
I am low volts okay so those are two
ways of conceptualizing those things
notice that depending on the ratio of
volts to amps in both of these cases we
might have exactly the same number of
Watts you just have it distributed in a
slightly different way what's what are
what are watts when you think about
Watts Watts are the capability of the
electricity to do work okay so let's say
that I have I'm going back to the
previous line let's say that I have a
waterwheel that I want to turn okay I
could do that by pouring a lot of water
at low pressure until the weight just
gets so heavy think about like a river
flowing by right a river is not very
high pressure but if you're up to your
waist in a river it can just have so
much water pushing on you that it can
knock you over okay now think of
something like a very very high pressure
garden hose like a fire hose right a
fire hose is not put well fire hose
actually is putting out quite a volume
of water but not as much water as that
River
it's but is putting it out at a very
high pressure and both of those things I
could shoot the water wheel with a high
pressure low current flow or I could
dump a low pressure high current flow on
the water wheel and either way I could
get it turning okay go with that go with
that the idea is that as long as the
watts are the same you can get the same
amount of work out of the electricity so
you could have high volts and low amps
you have low amps and high volts and and
you could get the same amount of Watts
out of it
watts do work amps make heat now this
can be a little confusing because if you
talk about the heat dissipated by a
resistor or by a wire it will be given
in watts heat dissipated is given in the
unit of watts and this is a little
confusing and I don't want to go into
that too much because I feel like it's a
little bit of a distraction but
basically when you're assessing the
amount of heat that a given electrical
circuit is going to sustain that is
calculated based on the amps going
through it and this is why you folks
over in countries that use 240 volt
electricity can have thinner wires in
your walls and still get more power out
of your electrical receptacles you can
have a 3000 watt tea kettle and we at
America can't can't get that and the
reason is that in America we only have
120 volts so we need we have half the
volts so we need twice the amps to make
the same amount of Watts twice the amps
going through the wire means twice the
heat generated and that's the limiting
factor on how much current that's why
you have a 15 or a 20 amp breaker if
you're in the US anyway in your interest
in your breaker box the goal there is
that if you were to pull more than 15 or
20 amps then you would dissipate so much
heat into the wires that you could have
a fire hazard
okay so amps make Heat watts do work and
what that means is that because of the
relationship volts times amps egal watts
higher volts means you can have lower
amps and less heat for the same amount
of work
okay so 240 volts gets you more
x4 less amps and therefore less heat is
generated well that's good right so why
don't we all just use of 400 volt earth
the one kilovolt electrical circuitry
right and just have very very low amps
with less heat well the reason for that
is that higher volts are also much more
dangerous to humans and at a certain
point you you you don't want that but
that's what that is one reason and again
this is a complex topic that we won't go
off on a bunny trail on but that's one
reason why DT high high voltage lines
that go across across the city you know
those things are up at kilovolt ranges
right because you have less amps and
less heat for the same work less
resistive losses and I know if you know
about how electrical power systems are
run that there's more to it than just
higher volts equals less amps it's not
it's AC that's something different let's
not go into it but that's the gist of it
okay so got all that let's keep going
heat dissipated as a function of the
resistance of the circuit so low
resistance circuits won't actually see
much difference between high and low
voltage in theory if you had a zero
resistance circuit well then the current
flow would be infinite for any ahmed's
that's not the point
but the heat dissipated goes up as a
function of both the current it's its
current squared times resistance so if
resistance is low then the difference
between a higher and a low current won't
be or high to low volts won't be as
significant and the reason I point this
out is that if you've got a multi rotor
with a you know and two inches of wire
between the PDB and the ESC the
resistive losses in that wire are going
to be really low and there are
advantages to going say from 3 s to 4 s
2 6 s but the advantages are not really
like the in the reduced resistive loss
in the wires because the resistive
losses already so low because it's such
a low resistance circuit to begin with
ok that's why I point that out but we
are not talking about motors or ESC s at
the moment
we're talking about battery chargers and
battery charges are basically just
voltage converters they take an input
voltage and they turn it into an output
voltage and that output voltage is
carefully controlled to charge your
batteries and and so we when we think
about battery chargers or voltage
converters the one of the key things
that we need to be aware of is that
watts in equals Watts out times
efficiency now the reason this is going
to matter is because your battery
converter or your battery charger is
going to be rated at a certain number of
watts and there's it's going to be
limited in the amount of power it can
take in and limited in the amount of
power it can take out and as we think
about all that stuff that's going to
determine how fast we can charge our
batteries and potentially which voltage
which battery charging you were going to
decide to buy okay so let's just take an
example here here is a Pololu regulator
that we're all probably have experience
with or are familiar with if we assume
that that is a five volt regulator and
it's putting out 500 milliamps at 85%
efficiency five volts times 500
milliamps equals 2.5 watts if we divided
by the efficiency factor we get 2.9
watts so it is using 2.9 watts if the
input voltage was 9 volts then 2.9 watts
divided by 9 volts means it will be take
in 0.32 amps or 300 20 milliamps at 9
volts at 12 volts it would take in 260
million s okay but again Watts in equals
Watts out times efficiency that's the
basic equation so in summary as the
input voltage goes up the input current
will go down for a fixed output as the
input voltage goes down the input
current will go up and therefore heat
dissipated goes up and this is
significant one of the things that we're
going to see as we get into the voltage
chart are the sorry the battery charger
specs is that the battery charges like
it's typical to see the battery charger
have an input voltage range of between
10 and 18 volts and it's full output
a power can only be achieved if it's
inputting at at the higher voltage at
the lower input voltage it will need
higher input current and too much heat
will be generated and it'll have to have
less output we'll take a look at that as
we go into in there so so but but we
need to understand that the higher your
input voltage the less heat you will
dissipate the and and the more power you
can output for the same amount of
current this all assumes a switched mode
regulator which is what battery chargers
are but if you had a linear regulator
like on your PDB or something you should
be aware that linear regulators drop
voltage just by converting the power to
heat and with linear regulators the heat
dissipated goes up as the difference
between the input and the output voltage
goes up so with switched regulators in
general the higher your input voltage
the less current you will draw and the
less heat you will dissipate and so it's
generally good with a switch regulator
to give it a higher input voltage
because you'll generally get more
efficiency but let's check this check
the datasheet to be sure but with
switched regular with linear regulators
it is always the case that the higher
the input voltage the more heat you will
dissipate and in general with a linear
regulator you want the input voltage to
only be about maybe a volt and a half to
two volts just higher than the dropout
voltage but not much higher if you can
possibly avoid it because you're going
to be wasting a lot of power as heat
well and just also perhaps just don't
use linear regulators there they have
their they have their place right
they're cheap as beans as Bruce likes to
say and and easy to work with but but
they certainly they have they have to be
used in the right place if you have a
large input voltage and a low output
voltage you're going to get tons of heat
you're going to need a big heat sink and
it's just not worth it ok everything
I've said here is a bit of a
simplification for example efficiency is
not a fixed number but efficiency varies
according to the output current and the
input voltage we're going to ignore that
for the time being I just want you to
get the con
up that watts in equals watts out so if
you're putting out 5 volts 500 milliamps
multiplied by the efficiency factor you
say that's 2.9 watts and you know that
whatever your input voltage is you have
to have 2.9 watts coming in okay you
can't you can't get free energy from
nothing okay so if you really want to
know about this stuff check the
datasheet from the manufacturer well I
see that I'm now 13 almost 14 minutes
into this video so instead of getting
into this awesome spreadsheet that I've
made hahaha I'm just going to tease you
with it I'm going to end the video here
and I'm going to put the next batch of
content into the next video because I
feel like 15 minutes is a pretty good
length for a video and I feel like we've
covered a good amount of information so
I hope that was helpful
happy flying see you next time
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