Amp Hours and Watt Hours Explained in Solar Power Systems (Ah and Wh)

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When exploring the world of batteries, two terms often pop up: 'amp-hour' and 'watt-hours'. But what's the difference? Let's break it down.
First up, amp-hour.
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Amp-hour, abbreviated as 'Ah', is a measure of a battery's electrical storage capacity. It tells you how much current a battery can theoretically provide over a period of time.
You can have a 100Ah battery at 12V, a 100Ah battery at 24V or a server rack of 100Ah at 48V. All of these batteries have a different energy capacity. Now when someone asks how big your battery is, you shouldn’t say its 100Ah, because it depends on the voltage of the battery.
That’s why we will use Watt hours to accurately measure the energy capacity of a battery. Because Watt hour takes into account the voltage of the battery.
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Watt-hours, or 'Wh', represent the total energy a battery holds. It's the product of the battery's voltage and its capacity in amp-hours.
For instance, a 12V battery rated at 100Ah stores 1200 watt-hours of energy. While the 100Ah battery at 24Volts stores double that for a total of 2400 Watt hours. Or a 48Volt 100Ah battery that stores 4800Watt hours of energy.
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This watt hour rating gives a clearer picture of how long a battery can power a device. If a fan requires 100 watts to run, the 1200Wh battery can theoretically power this for 12 hours. Because 1200Wh/100W=12 hours. I say theoretically because a battery should never be discharged to 0%, whether it be lead-acid of lithium. Use 50% of the capacity for a lead-acid battery and 80% for a lithium-iron phosphate battery.
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In essence, amp-hours give insight into a battery's capacity, watt-hours reveal the total energy it can store. So why do we use Amp hours? This should be used to calculate the charge and discharge rate of a battery, also called C-rate.
The C-rate of a lithium battery is 1C while it is 0.2C for a lead-acid battery. Knowing this, we can calculate the maximum charge and discharge current for the battery under normal conditions.
For example a 100Ah lithium battery can provide a current of 100Amps. while a lead-acid battery can only provide a current of 20Amps. A battery can provide more current, but that will decrease it’s lifespan because the cells will degrade faster.
I talk more about C-rate in my dedicated video about it. There will be a link in the description.
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Did you like this explanation? Give it a thumbs up, and subscribe for more off-grid solar tutorials. Do you have video suggestions? Let me know in the comments and I will make a video about it.
And before you go! If you're interested in off-grid solar power, I'm giving away 7 different diagrams that you can use for your projects. These diagrams are designed to help you set up your solar system efficiently.
All you have to do is click the link below, provide your email, and I'll send them your way.
00:00 Introduction
00:10 Amp Hours
01:10 Watt hours
01:48 Charge/Discharge time
02:35 Why use Ah?
03:41 Outro

[@RobertCOVELL]

I love how this goes right over my head

[@adex2000ng]

Great video with very clear explanation. Thanks a million ....from Nigeria

[@brianOcurradhin]

Many thanks for this I've just started designing the system I will need off grid and your site has really good info that helps alot

[@johnm249]

This video is so good you got me to subscribe in less than 4 minutes and 16 seconds.

[@darrellfort1668]

thanks

[@Ghedi1965]

Thank you for your valuable information on your channel. It is my first time and subscribed.

[@fb510m]

Very clear; thank you!!!

[@mr.c6674]

Excellent explaination. This helps clear up information on solar system builds. Thanks for the video.

[@cleversolarpower]

Thank you for the comment!

[@handjgerhardt7391]

Very well explained and much appreciated. Thank you!

[@cleversolarpower]

Glad you enjoyed it!

[@changurr2705]

awesome. I've been trying to figure wh's and such.

[@tesfahuntilahun1038]

An excellent explanation ❤❤❤

[@mindofown]

Excellent thankyou

[@--KARA--]

So good explanation

[@cleversolarpower]

Glad you liked it

[@Mathshaven]

Very consise presentation

[@adivasworld7466]

Great explanation! I'm considering several alternative power sources. I notice small "Power Stations" like Eco Flo River 2 and Blueletti EB3 advertise less watt hour than their rated watts (ie 258wh, 600W, 1200W surge), How are these things possibly ever achieving the higher watts? I'm wondering if it's false advertisement or they have built in second battery to handle short peaks. Any thoughts?

[@mudivince7709]

Cool

[@michaelanderson2166]

Isn’t a watt-hour just 3600 joules?

[@theusconstitution1776]

So if I have 212 V lithium ion batteries that are 300 amp hours and 3840 W hours and I wire them in series will the hours double?

[@cleversolarpower]

You have made a 24V 300ah battery. But the total power stays the same when you wire in series or parallel. Checkout my video about series/parallel wiring of batteries.

[@brianOcurradhin]

I want to run a 24v 1.8amp 45w chest freezer, I need at least 7 days running before I need to recharge the battery. I would use 2 lifepo4 12v in series, Q: what amp hour capacity would work in this case, thank you

[@cleversolarpower]

45W*12h*7days=3780Wh approximately with a 0.5 duty cycle of the freezer (which is high). 3780Wh*1.2 (only use 80% of the battery capacity)= 4500Wh -> 4500Wh/24V=187Ah @ 24V. Total = 4 12V 100Ah batteries.

[@brianOcurradhin]

That's fantastic I can buy 1 x 100ah lifepo4 at a time for around $350nzd which is affordable thank you so much I really enjoy watching your channel there's alot of stuff about solar set ups but I like this 👍

[@edwinapolinario1382]

Sir am a pilipino in our country we pure joy sun supicien to support the battery.according to some bloggers in KZbin it takes 5 hour to fully charge a100 watts sollar panel to 100 amps battery.is it safe for me to use a 5peaces 100watts each sollar panel one peace battery for me fully charge it in one our?

[@cleversolarpower]

I will make a video about it soon.

[@13Dollar83]

❤❤

[@judenoukui550]

Please can you send me the diagram?

[@cleversolarpower]

You can get it through the link in the description.

[@mudivince7709]

Didn't see the link

[@cleversolarpower]

Sorry! It is fixed now 😉

[@johnm249]

I have your book. I need to get organized, clean my apartment, box up a lot of stuff. Then start to put a portable solar system together. I am gonna live the van life for 4 months to save money. Gonna work and sleep in van. I need enough battery power to run a mini fridge and 5000watt airconditioner 24/7. This is because I want to keep my dog cool in the heat during the day when I work. Plus keep us both cool at night. Plus I need to keep food cold too.