Battery charger fundamentals: Watts, Volts, Amps

Summary

In 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

00:00

🔋 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.

05:01

🔌 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.

10:05

📈 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.

Keywords

💡Battery Charger

A battery charger is a device used to supply energy to recharge the batteries. In the video, the user discusses their current charger, an 'aquiescent 650 watt charger', and their desire for a more powerful one due to its slow charging speed. The theme revolves around understanding the specifications and fundamentals of battery chargers to make an informed purchase.

💡Parallel Charging

Parallel charging refers to the method of charging multiple batteries simultaneously by connecting them in parallel to a charger. The script mentions that the user charges four of their 1300mAh batteries in parallel but finds the process slow, indicating the need for a charger capable of higher current delivery.

💡Wattage

Wattage is a measure of power, calculated as the product of volts and amps (Watts = Volts × Amps). The video explains the concept of watts in the context of battery chargers, emphasizing that higher wattage chargers can deliver more power and potentially charge batteries faster.

💡Voltage

Voltage, measured in volts, is the electric potential difference between two points. The script uses the analogy of water pressure to explain voltage, noting that a high-voltage, low-amperage scenario is akin to a high-pressure water jet, which relates to the charger's ability to deliver power.

💡Amperage

Amperage, measured in amps, is the rate of electric charge flow. The script likens amperage to the flow rate of water, explaining that a high amperage, low-voltage scenario is similar to a drainage culvert with a high flow rate but low pressure, which is crucial for understanding how chargers can charge batteries at different rates.

💡Efficiency

Efficiency in the context of battery chargers refers to the ratio of output power to input power. The script mentions that the charger's efficiency affects the amount of power it can deliver and the heat it generates, which is important for understanding the performance and safety of the charger.

💡Heat Dissipation

Heat dissipation is the process of releasing heat generated by electrical components. The video explains that heat is generated by the current flowing through a circuit and that higher amperage or lower voltage can lead to more heat dissipation, which is a critical factor in charger design and safety.

💡Switched Mode Regulator

A switched mode regulator is a type of power supply that uses switching elements to regulate voltage. The script points out that switched mode regulators are more efficient than linear regulators, especially when dealing with high input voltages, making them suitable for battery chargers.

💡Linear Regulator

A linear regulator is a device that maintains a constant output voltage by dropping any excess voltage as heat. The video contrasts linear regulators with switched mode regulators, noting that the former is less efficient and generates more heat when the input and output voltages are far apart.

💡Power Rating

The power rating of a charger is the maximum power it can handle, measured in watts. The script discusses how the power rating of a charger limits the speed at which batteries can be charged, and it's a key specification to consider when selecting a new charger.

💡C-Rating

The C-rating of a battery refers to its capacity to deliver current, expressed in hours (e.g., a 1C rate means the battery can deliver its full charge in one hour). The script mentions that the user's batteries can charge at 1C or even 2-3C, indicating a desire for a charger capable of higher current delivery to match the batteries' capabilities.

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