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2023-11: Warosu is now out of extended maintenance.

/diy/ - Do It Yourself

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1596533 No.1596533 [Reply] [Original]

How many kilo-watt hours can you pack in the volume of a backpack? I'm guessing laptop batteries have the biggest energy density per volume?

>> No.1596539

>>1596533
>doesn't understand battery technology or electricity/electronics
The issue isn't how much power you can """steal""", it's how long any worthwhile amount of power you can get because of how long it'll take to charge a battery pack sizeable enough to make any difference.
Then there's the weight of the backpack, and the fact that you're essentially carrying around a very expensive firebomb on your back; any Li+ battery pack big enough to matter in this context would weigh at least 50 pounds, and if even *one cell* in it went bad and overheated, the resulting cascade failure of the entire pack would cause a huge firebomb explosion.
Then there's the fact that you'd have to charge such a thing hundreds of times at least before it'd pay for itself.
>How many kilo-watt hours can you pack in the volume of a backpack?
Answer: not enough to make it practical.

>> No.1596548

The answer is around 400Wh which would run a crypto mining rig for maybe 24 minutes...

It would probably make more sense to charge up a car or something.

>> No.1596580

>>1596533
Consider a deep cycle marine battery. Like a car battery, it’ll fit in a gym bag.

>> No.1597109

Stihl sells a 36 volt battery backpack with 1100 watt hours for 1100 bucks. If you wanted to use that to steal energy you could get about 1/3 of a kilowatt of AC energy out of it.
Out here electricity at the peak rate is 19 cents a kilowatt, which is probably much more expensive than most burger rates, so at best you'll get 6 cents of energy.

>> No.1597111

>>1596548
That's like 5cents worth of electricity.

>> No.1597116

>>1596580
>it’ll fit in a gym bag.
Bonus, no need to go to the gym if you lug a DCMB around in a gym bag.

>> No.1597562

>>1596533
Sounds like you're Italian.

>3 kilowatts (+10% for 15 minutes only) 230V per household
>~$50/month flat expenses, plus ~$0.15 to ~$0.30 per kilowatt/hour depending on day hour
>no incentive to add solar panels and shit
>a single unpaid bill may have you immediately tuned down to max 0.4 kilowatts

>> No.1597568

>>1596533
I used to run bitcoin miners in my dorm where i didn't pay for power. Kept my room nice and toasty. Ended up selling the miners for a profit after making a good profit. Also somehow got a free gaming laptop from tigerdirect (shipping error they never caught) that I mined on and then sold hehe

>> No.1597573
File: 106 KB, 720x960, 1554063348006.jpg [View same] [iqdb] [saucenao] [google]
1597573

>>1596533
I L L E G A L

>> No.1597621

>>1597109
goddamn electricity is cheap. what a time to be alive

>> No.1597635

/diy/ - misinformation and idiocy

OK, what country?
I will guess the US from the pic you posted and the fact that you didnt say UNI.
Now, almost certainly your work/schook will not have larger amperage plugs just laying around. So you will be pulling from a single plug circuit basically.
This plug circuit is either 15A or 20A at 110v. There is a standard for the plugs, but no one hardly follows it so the only good way to tell is to make it go bang or have access to the circuit panel. So assuming the BEST case, you have a 20A circuit.
There will be shit on this circuit though, so you cant just have ALL of it. Assume it just has a few amps, say 3A at most on the circuit. You do not want to load a circuit 100% either, some say 80% at most, but fuck that I say 90%.
Ok so that's 18A max from the breaker, 3A reserved for other things so it doesnt trip all the time, leaving you with a nice even 15A at 110v

So just simple math from here. 1.6KW/h is your fucking answer.
Say you have access to said supply for 9 hours a day (work). That's 14.8KW. Or about $3-4
So the current most dense batteries are the panasonic ncr18650b cells iirc. I've personally tested them out to about 10Wh of storage per cell.
So you'll need 1,480 of these cells for said capacity. This will be 68KG of weight in JUST the batteries. Assume 80KG total weight including charging, all the solder tabs, ect. oh, 180lbs in burger units, or 150lbs in just batteries. Still doable in backpack form if you are quite strong.
Ok so the volume of these cells. let's shoot for a brick size. 30.5cm x 30cm x 65cm (height of cells) is 324 cells. Four high, or 26cm is almost 1300, just fill in some space or make it a bit bigger, lets say the final pack in burger would be 13inx12inx11in.
That's backpack sized I guess, so you're good there.

Ok let's round this up.
You will have to have a backpack capable of a cubic foot space.
The backpack will weigh 180lbs
The batteries alone will cost $15,000
For $4 worth of power

>> No.1598080

>>1597635
80kw*1m/s = 80watts just to haul that fucker around. That's 69 calories of food you'd have to eat for every hour you haul that thing around. That will "eat" into your profits heh heh.

>> No.1598082

Store it in water, it's pretty dense so it should store a ton of electricity. Just run wires from the outlet right into a backpack full of water.

>> No.1598090

>>1598082
Water isn't very dense relative to other materials. 1kg/L.

>> No.1598158

>>1598080
You forgot part of the equation for work (cos of the angle between movement direction and applied force, which for 90 degrees is zero). Only physical work performed is the one used to overcome air drag, at least if you are walking on level ground. Kinda counter intuitive, but physical work is measure of energy change, and moving an object on level ground doesn't change its energy.
tl;dr
Fuck off with using watts for carrying shit around.

>> No.1598160

>>1596533
>get really long cable
>plug one end in school/work socket
>run it to your home
>cover it in leafs

>> No.1598319

>>1596533
Yes you can charge your laptop at work or school and if you're lucky maybe even your electric vehicle without people noticing.

>> No.1598727

>>1598158
Energy is force times distance. Watts is energy divided by time. It doesn't matter if there was useful work done, he still burned the energy in a set amount of time which is measured in watts, which can be converted to calories burned.

>as long as you move on level ground you aren't consuming energy over time
Absolutely wrong, you need to go back to high school.

>> No.1598729

>>1596533
>electric bike batteries
i used to charge them at my workplace because free power.
i always charge all 3 of my batteries because i use them all up for going to the supermarket or into town or just riding around.
inb4 bike hate, in the netherlands, its quite common to ride a bike, and cyclists aren´t annoying for cars because we have special bike lanes and a culture build around bikes.

>> No.1598730

>>1598727
Time cos of the angle.
It's the most basic shit my nigga.
https://en.wikipedia.org/wiki/Work_(physics)
Energy used by a human can't be calculated from this simple equation.

>> No.1598739

>>1596533
>Spending a couple hundred dollars on batteries just to steal $0.25 worth of electricity each time you charge it.
How fucking stupid are you?

>> No.1598749

>>1598730
>In physics, a force is said to do work if, when acting, there is a displacement of the point of application in the direction of the force.

He's doing work in moving the object, if anything he's expending more energy than I calculated to move 80kg of batteries because the force he's applying to move the object isn't in the same plane. However, when I converted over to calories I included an approximation of the human bodies efficiency. Regardless he still needs to use a minimum of what I calculated to move the 80kg bag at just below average walking speed.

>> No.1598754

>>1598727
>>1598749

The fact that this is even being discussed non-ironically is proof that the autism level around here approaches that of /sci/.

>> No.1598798

>>1598749
The direction of most of the force is upwards tho, the force needed to overcome air drag at walking speed is negligible. This doesn't say what you think it says.
Cos 90 degrees is 0 my friend. Human is using up calories, but they cannnot be calculated with the F*r*cos(F, r) equation with any accuracy (force needed to overcome air drag is a minuscule part of the problem at those speeds), because the angle between movement vector and the force counter acting gravity is 90 degrees, the calculation will come up to 0.
Read up on trigonometry and come back.

>> No.1598807
File: 67 KB, 1000x1000, 61d9mhYNt8L._SL1000_.jpg [View same] [iqdb] [saucenao] [google]
1598807

$70
1.6 lbs
800a
has a massive pair of nipple clamps

win/win.

>> No.1598810

>>1598798
W = F*s = m*a*s.
When you walk you basically accelerate and break with every step, so it would be pretty constant.

>> No.1598847

>>1598810
I think you keep same speed +/g same speed. Anyway it's not as easy as your first post seemed to imply.

>> No.1598851

I bought a 337Wh lipo for $400 after shipping. It weighs 7lbs and holds 2.7 cents worth of power. Have fun.

>> No.1598863

>>1598847
not the same guy

>> No.1598870

>>1598160
>>cover it in leafs
You don't think a row of prone Canadians would be a bit obvious?

>> No.1598895

>>1596533
>>1597635
My work has electric car charging stations that employees can use for free. How would that change the equation if I managed to switch a standard us plug with an EV one?

>> No.1598900

>>1598895
>My work

Presumably you get paid. Stop thinking about petty theft and concentrate on doing a good job, and in the long run you will be far better off in more ways than one.

>> No.1598903

>>1596539
>Answer: not enough to make it practical.

Depends. Maybe he's German.

>> No.1598919

>>1598900

Better answer.

>> No.1598988

>>1598798
But it's not cos 90 is like cos 60 at most which is 0.5. And like I fucking said, I used a conversion to calories which takes into account shit like that.

>> No.1598999

>>1598895
Irrelevant, in this situation you're limited by the weight of the batteries you can carry.

>> No.1599095

>>1598810
>When you walk you basically accelerate and break with every step
Wow, I didn't realise I walked so goofily.

>> No.1599131

>>1597111
In the US, but things are very expensive in Yurop

>> No.1599135

>>1598160
I think I'd add 220-1000V transformator, so nobody down the line can't steal your stolen electrocity.

>> No.1599153

>Stealing electricity

what a fucking nigger

>> No.1599359

>>1596533
Here's a better question:
Does that even make any economic sense?
Electricity is like 12¢ per kilowatt hour, and you're probably going to spend about $150 to $300 making such a battery backpack.
Assuming you can store 1 KW/hr in the backpack, and you charge it once per day, it would take over 4 years for you to break even.

>> No.1599366

>>1599131
It's still not more than 10cent in Europe

>> No.1599373

>>1599366
Germanistan reporting in. It's 30 cent here.

>> No.1599387

>>1599373
That would be the price for 1 kWh, which we weren't talking about.

>> No.1599486

>>1599373
>>1599387
In the UK it's about .15USD for a kWh, even cheaper on some tarrifs at off peak.

Here's where y'all can be jelly: couple of pence for a kWh of natural gas. Imagine if you only had to pay a bit over 1 or 2 cents per kWh to heat your home Amerifats.

>> No.1599499

>>1599486
Oy! You 'ave a loicense for that fork?

>> No.1599546

>>1599486
Are you trying to imply that American homes don't have natural gas heating?

>> No.1599636

>>1599546
Burger reporting. I pay $10/mo just for the privilege of paying 56 cents/therm.

I'm pretty sure he wasn't suggesting that supply was the problem.

>> No.1599667

OP, here is the cheapest option, find a broken UPS

Most people toss them when the battery is expired, find yourself a replacement battery and you will be good to go. Any 12V SLA battery will do

>> No.1599853

>>1598798
this

>>1598810
yes you accelerate your body parts but there is no force other than gravity and other irrelevant factors like air drag. The work done is zero. If you factor out the energy you need to just stay alive there's nearly nothing left. Walking is very efficient. It's a different thing with climbing as you actually move non orthogonaly to a force and work is done. But still compared to your normal body functions the work is completely irrelevant.

>> No.1599857

>>1599853
>yes you accelerate your body parts but there is no force other than gravity and other irrelevant factors like air drag. The work done is zero.
Accelerating and De-accelerating mass alone is work, even without gravity and air.

>> No.1599862

>>1599857
Hes confusing potential energy with force.

>> No.1600112

>>1596533
>stealing electricity
Any quantity worth stealing isn't going to be able to be stored, secondly, electricity isn't that fucking expensive, just pay for it, dipshit.
>batteries
Even if we're assuming you're a homelessfag, and even a small amount of power makes a difference, you wouldn't want to use batteries alone, you'd want a system using both lead-acids and super-capacitors.

>> No.1600125

>>1597111
Or 5 pennies