Welcome to my battery capacity tutorial.

I’m going to talk about amps, amp-hours, watt-hours, C ratings, and other important things that you need

to know when working with batteries. First I’d like to talk about a common

question people have. Let’s say a battery like this is capable

of delivering one amp. Just because a battery (or any power

source) is capable of delivering one amp, it doesn’t mean that if you connect it to

something it will definitely supply one amp. Voltage sources like batteries will only

deliver as much current as the load needs. The amount that the load draws depends

on the load. It could be a low resistance load that draws a lot of

current… a high resistance load that draws barely

any current… or it could be a complicated digital device like this microcontroller which draws a different amount of

current depending on what it’s doing. This 2Ah battery is capable of

delivering over 4 amps, but with the motor I have connected to

it, it’s only delivering 2mA. And it can do it for hundreds of hours.

If you’re confused so far keep watching! The first thing that you

need to understand is that amps and amp-hours are two completely

different things. You’ve heard about amps or amperes

before. That’s a unit to describe how much electrical current is flowing. But what is an amp-hour? An amp-hour is a

completely different unit. It’s a measure of capacity, and it’s a

way to help estimate the amount of energy that a battery can hold. For example, here we have a rechargeable

AA battery. The capacity is 2000mAh, or 2Ah (2 amp-hours). The simple explanation of what this

means is that it can supply two amps for one hour until the battery runs out of energy. Two

amps multiplied by one hour is 2 amp-hours. If we draw less current, the battery lasts longer. It could

deliver one amp for two hours. And if we draw more current the battery

gets drained faster. It can deliver 4 amps for half an hour.

So amp-hours are simple way of estimating battery life. And in general, capacity (in amp-hours)

divided by the load (in amps) gives you the battery life (in hours). So

does that mean that this battery can deliver a 120 amps for one minute? Let’s try! Hmmm it seems the battery is

only able to supply 9 amps. And its heating up a lot. Let’s Google

the data sheet of the battery and see what the limitation is. Take a look at this. This battery has an

internal impedance of 25 milliohms. So it’s

kind of like there’s a little resistor inside the battery… but in reality it’s going to be a

limitation of the battery’s chemical reaction and electrodes. This internal impedance limits the

amount of current that the battery can deliver and from electronics perspective

it effectively becomes the source of heat when the battery is delivering current. This explains why very few batteries can

actually deliver 120 amps. And it raises the question… how much

current can a battery safely deliver? A little lower in the datasheet we can

see the discharge curves of the battery, ranging from 400mA to 4A.

So it’s implied that we probably shouldn’t be discharging this battery at a rate higher than 4 amps. (oops!)

Also take a look at this… notice how the effective capacity

changes depending on how fast we discharge the battery. this is only a 2 amp hour battery when

we discharge it at under 400mA. If we discharge

it at 4 amps the effective capacity is only 1.7 amp-hours because now we’re losing a lot more

energy in the form of internal heating. And the overall trend is that the more

current we draw, the lower the output voltage will be

because we’re dropping voltage across the internal resistance of the battery. So this 1.2 volt 2 amp-hour rating is only a guideline of what you can

expect to see under ideal conditions. Okay that’s amp-hours. Now here’s

something to get you thinking. This is a 1.2 volt 2 amp-hour battery. Over here we have a 9.6 volt 2 amp-hour

battery pack. So if these are both 2 amp-hour

batteries, do they both hold the same amount of energy? Of course not! The 1.2 volt battery will

theoretically deliver two amps for one hour with a voltage of around 1.2 volts. The

9.6 volt battery pack will also theoretically deliver two amps for one

hour but with a voltage around 9.6 volts. So one way we can compare the stored

energy of these two batteries is to use another unit called watt-hours. Volts x amps=watts. So you

can probably guess that volts x amp-hours=watt-hours. The single cell has a

capacity of 2.4 watt-hours and the larger battery pack has a

capacity of 19.2 watt-hours. Now it’s more obvious which battery

stores more energy because we’re comparing apples to apples and watt-hours to watt-hours. Now let’s talk about C ratings. Here

are two batteries that seem identical. They both have a nominal voltage of 11.1 volts and a capacity of 2200mAh. They look the same but one of them has a

20C rating and the other is rated at 40C. But what

is a C rating? The C rating is an informal way of

describing how much current the battery can safely deliver. If you show a battery discharge curve

like this to most people they’ll have no idea what it means. And

it’s not very exciting marketing material. So marketers like use C ratings instead.

The “C” refers to the battery’s capacity in amp-hours. So this 20C battery can deliver 20xC, or 20 x 2.2Ah, so this

battery can safely deliver up to 44 amps. And this 40C battery can safely

deliver 88 amps. Now are you confused? Because you should

be. Remember that amps and amp-hours are completely

different units. C ratings are confusing because they screw up the

units. You multiply the amp-hour capacity by the

C rating and then you pretend the result is in amps. Finally I can’t make a video about amp-hours

without mentioning The Amp Hour, a podcast for electrical engineers. Check

out the link in the video description! Thank you for watching and check out the

video description section for a link to see how you can support the channel. I’ve got some new merchandise like

t-shirts and mugs that you can buy!

Disposable batteries have a high internal resistance, so battery life is much more complex

Simple and clear explanation. Thanks!

Hi. how many 18650 3.7 volts. 3000 mAh, the pairs need 96 volts, 150 AH. 15 kwh? Thank you

Very clear. Thank you.

Thanks for the information!

Looking for that merch there bro, can't find it

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So my question is this and I used to know the equation. In real life I have a battery operated WIFI camera it uses 4AA they last about 2weeks. Using good quality Akaline batteries.

That is 6 volts in school we were told this is "pressure" so to speak.

The batteries list 2200 mAh so this is capacity of electricity 2.2 amps of "current" will drain them in one hour.

I want to remove the AA and wire up a 2 cell lipo 20c. 7-8volts. 3000 mAh.

So do I figure the Watt hour to determine how long the lipo will last apposed to the AA.

I have completely forgot how to figure the "time" it will last.

Or would ysing a 3cell 12v lipo be the answer to look get use?

can't believe I have forgot a lot of this. Back in 1994 when I earned my degree in applied science I could figure it my head.

Thank you so much

Thanks! Now I feel like I know less than before watching this video.

Hey i have done it practically according to you,

i have 3 AAA 1.2V and 1100mAh batteries connected in series , i have connected LED across batteries in series with a 100ohm resister. what i can measure is current drawn by that LED is 40mA, so now to calculate the hours = 1100mAh/40mA== 27.5 hours.

if i apply same thing for wAh, that is Total Wah=(1.2+1.2+1.2)*1100==3960mwh,

and the voltage drop across LED is 2V and Current drawn is 40mA, so Total Watts=2*40=80mW.

but if i want to calculate hours, i.e== 3960mWh/80mW==49.5 hours.

In Both case Result is different, i.e one is 27.5 hours and 49.5 hours.

which one we should Consider??

please Replay

Good video….no gibberish. …fluent. ..

Great video

If I have a 3.6 v 5000mAh battery and it has a discharge rate of 3Amps does that mean I get 3amps or 5000 mAh. I guess what I’m asking is I don’t want to go over my rated amps on my motor and I am curious to know how reliable these ratings are and what one I should use for my calculations. Thanks.

I've been waiting for a long time to hear these terms and processes explained to me. Thanks!

thanks man .. it is a grat video and useful 🙂

Why thumbs down.

I am confused

very nice sir..thanx

Good video

Your videos are awesome. Could you please make a video explaining what it means for a electrical component to draw too much current?

Thank you that was helpful

i have been looking at tons of batteries on the web….6v,12, assorted amps, etc. I have even looked at step-up dc/dc coverters….12>24 and 24>48…….i am looking to power a 48v 1000watt brushless,gearless ebike motor hub…..those lithium battery packs cost more than my trike and ebike conversion kit COMBINED…..so i have been exploring the SLA battery configs…… thankyou for this video….i dont have an apple to put on your desk but is it OK if i go to the playground a little early ?

OMG, now I feel retarded… 🙁

soo much confusing what are watt-hours? what is C rating??

U cleared every dought sir 👌👍

Where did you come up of the idea that the battery can carry a capacity of 120A in one minute?

About the C rating, if the battery is 2.2Ah and its C rating is 44A, how long (time) can it supply at 44A?

I have a question. If you would use two of those 20C batteries, would that mean you could provide safely the same current as that one 40C battery? It doesn't seem to me like you would. But I wanna be sure 😀

so basically [C]=[1/h]

Finally!!!! I understand now… Sheesh!!

thank you for this fantastic video!

It was helpful

took YouTube forever but it finally recommended me something useful, this is probably the best explaination of Ah, A, Wh and C I've ever come across. Definitely looking at batteries in a much more reasonable way now.

C = (max. continuous discharge current) / (nom. 1-h discharge current).

this is a great video. thank you. I have a question. I have a cordless vacuum, its rechargeable battery pack needs to be replaced, however, it has been discontinued. It is 4.8v 1.3Ah. I wonder I can simply get 4 AA rechargeable batteries bundled up to replace this old one? thank you very much

u really rocked it bro…..it is very easy to understand by way u teach…

What is the c rating of a 18650 battery? Where can you find it on the battery? For example on the Samsung INR18650-25R 2500mAh battery

Thanks for the valuable information you provided.

Can you explain what does the "initial current less than 60A" written on the side of a Gel 200Ah battery mean?

I couldn't afford to buy your t-shirt or mugs, I can only give you like.

thank you

great video !

thanks a lot!!!

Excellent video – thank you

I getting into rc builds with my son and O'boy have we burned up batteries. I gotta watch this again 4 or 5 more time and take note…..again

Afrotechmods, your videos are really cool, thanks for making them. Can you help me with advice on which ones to watch so that I might understand how to power my 50 Watt RV fridge and 62 Watt CPAP (breathing machine) through the night? I am trying to build a system that has the battery capacity to power those and then use Renogy solar panels to recharge it during the day.

Still I'm confused which should I choose for my vape ? Anyone know ?

Nice explaination 🙂

i need to watch this twice

Love the video. Would like to know more about charging a SLA battery with solar panels and a charge control through an ammeter. How low should the ammeter show as the amperage drops when the batt. is charging ?When is a battery actually full? I am now subscribed to ur channel.

Wait, what hours again? 😀

sorry for the bad pun…

0:20 It's well established in electron theory that current (amps) travel from negative to positive, not positive to negative.

Great. Merci 🇫🇷

Ampere-hours is a unit of electric charge.

You talked about impedance in batteries. Is that even possible? Impedance, as far as I know, is only valid for AC circuits; batteries create DC circuits.

they should use Wh for capacity, and Amps instead of C rating..

You've cleared my confusions…thanks.

hello sir…

i want i ask you a question

suppose…

can i change a wireless headphone battery. if original battery Voltage: 3.7V

and Capacity: 180mAH and new battery voltage 3.7 and capacity 2500 to 3500 mAH

How bout sir a video of battery and charger

Hi sir i want to ask you something i have 6v 4,5ah battrey, how long if i charge the battrey with 0,43 amps??

Nice video

Well Done & Communicated

Thank you very helpful, by the way are you the voice of 'Talky the toaster' from Red Dwarf TV show?

As a neophyte battery pack builder, this was very helpful. Thanks! So, if the "C rating' is a marketing thing, should it be ignored?

If you're confused, you should be because this has not been explained adequately. Particularly in relation to C ratings. And not a mention of batter packs construction relating to series and parallel connection and how this relates to Amps Mah and C.

what differen if we or i set battery into parrarel or Seri?

Thanks Bro….

If i connected led at the end of 25c 3.7v 250MAH battery so it will work or not

Hey good video…

But ..

I watched to get some insight into a battery I have….

12v 46w 20 minutes.

So what's that in Ah?

Very helpful. Thank you

Great video! thanks!

I didn't got it, watt hour is it?

thanks great video

Thanks. It is clear.

YOU ARE A LEGEND

Good video

Brother 1k ohm resister how many voltage i can use it??? Or have a any rule for using resister in how many voltage??? Please answer me

Well explained! Thanks!

+ manufacturer bullshit info just to boost the sells. -10-20% from the manufacturers given amp hour and we are closer to reality.

Why do they advertise battery capacity in mAh instead of mWh? Watt-hours is more general. And why do they use a rating in thousands of milli-units? That's just extra tongue-wagging. And instead of a "C" rating, why don't they just tell you how many Amps it can safely deliver?

just think of A as Liter, makes sense very fast !

I have a 11.1 v bhr battery with 6000ahm. With 50c so 300 that looks to much

Best explanation I ever had, really good please keep up good work for us "slow learners"

Thanks for making this very clear for dummies like me to learn!

Awesome video

THANK YOU I ACTUALLY UNDERSTAND !

Thank you for screwing that up for me. ☺

Excuse me! It's mAh ah!

Thank u sir for tis infomtv vido

Nice

thank you very much!!!!!

abe lawade hindi ma guthiyay le tor gad fatathe

Am confused

Great video.

Looking at battery information is very confusing.

As a thought experiment: Say I wanted to create a electric vehicle with the smallest possible battery bank.

And charge the battery bank using a gas turbine generator.

What should I be looking for in a battery bank. High volts with less amph?

2:03 do you mean 33.33 A for 1 minute?

Awesome explanation

Nice video.. quite informative

Please translate to arabic subtitle

Doesnt electrical charge leave the negative terminal of the battery?

How to tell the mAH of a non-rechargeable batteries? For example an AA 1.5V batteries?

Watts the guy's name on second