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this post was submitted on 18 Mar 2024
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For the uneducated, what's wrong with it?
One running on "Volts" and another running on "Watts" is like refusing to compare two cars because one car runs on Wheels and the other running on Motors
Well, you just have to convert wheels to motors. A car runs on wheels, which is 1/4 motors. A boat runs on motors, and has one, meaning it has 4 wheels and is probably street legal!
Almost every sentence. But funny self review and other things aside, main problems:
"Watts... Contains." Is a fundamental confusion on what a watt is. It's like asking how much fast there is in a box.
The answer has a good basic idea, but also a total comprehension failure not just pulling the numbers out of thin air, but badly describing an equation with watts on one side and watt hours on another. The answer is both ignoring realities and getting the hypotheticals wrong. Sounds expertish but is both wrong and useless.
When they could have just said "yes, you could use a suitable inverter with a suitable battery and a fridge in some cases, but the math and actual connections would be more complicated than that explanation" or something like that.
Watt and volt are two different measures for electricity. Also your fridge will not work when hooked up to a car battery for many other technical reasons, including differ t voltages, and current types (AC/CD, not the band)
That’s wrong. Watt is a measure of power and volt measures….. voltage.
Charge (electricity) is measured in Coloumbs (sp?)
You need a complete circuit for Watts as P=iv.
I is current, measured in amperes
With the river analogy, Voltage = pressure, Wattage = how much water is passing, Current (Amps) is how wide the river is.
Pressure * Width of river = Amount of water passing
Not sure that helps with passing it through the terms and then to variables.
Water analogy works better with plumbing. A river, not so much. But people aren't that much better at understanding plumbing, unfortunately...
Volts measure voltage?
Tautologists study tautology tautologically.
The first rule of tautology club is the first rule of tautology club.
The first rule of tautology club is the first rule of tautology club.
Electrical potential, IIRC
Another way to think of it is this: Volts are like water pressure (potential energy) Amperage is like the flow rate of water Ohms (resistance) is like how hard it is to push water from high pressure to low pressure Watts are like the volume of water (a unit of energy)
A big hose has low resistance, water can move freely A coffee straw has large resistance, it's hard to pull and push water thru it
A river has very low water pressure, and the speed of the water can vary, so volume of water moving can be huge so the flow rate of water can be huge as well. A pressure washer might have very high pressure, but use as much water as a kitchen faucet. Certain applications need high pressure, some need low pressure. A car battery is like a river, low pressure (typically 12volts) but move a lot of amps (cold cranking amps of up to 500-600 ish usually), and a wall outlet by comparison is like a pressure washer with 120v, 15A (in the US). A fridge won't play nice on 12v, it needs 120v. It might need 400 watts which a car battery can do but it cares about how it can get that by requiring higher potential.
A watt, W=VA, can be thought of as asking how much water is there? 1 minute under a sink verse 1 minute in front a fire hose has two very very different amounts of water.
A watt hour, which most people are familiar with in the US for billing on their utilities, is like asking how many cups of water an hour. A light bulb needs a fraction of a kilowatt hour, a drier needs multiple kilowatt hours, but might only run for 30 minutes.
This idea gets a little tricky and falls apart at its edges but as a general idea should hold up for most peoples understanding of electrical stuff unless you work with it daily like an electrical engineer, electrician or something similar. For sanity sake I'm not going to try to apply this to AC verse DC, I don't have a good analogy for that
Obligatory mobile formatting heads-up and what not and I'm not caffeinated so meh
Ugh, you’re getting into the realm in which technicality is hard to explain.
That’s technically wrong. Even though ampere is coulomb/sec, electrons don’t actually flow.
Like I said it falls apart on its edges but for most people it's probably a better understanding of it than they will ever have or need, but most people scrolling thru Lemmy probably don't need to be understanding electrical concepts like electrons not actually flowing, charge, etc. I'm a controls engineer and while I am aware of the concepts and such, I am not designing electronics so at the end of the day I barely have a use for half of the concepts myself. Sure I could get down to the half semester class of quantum where things get weird, but that won't easily tell people to not to try to plug their fridge into a car battery
For the AC/DC part, I usually try to tell people it's like a water wheel that's been inserted into the hose of water. DC is it spinning one way constantly, while AC is it spinning back and forth. The wheel is turning pretty much the whole time (again, we can try to not be super specific with the way we do phases with AC), and thus you can use it to do stuff on AC or DC.
Clever, it just breaks down again with my analog of water volume lol. Definitely not saying it's wrong, I just like to leave it off so there are less questions haha
AC is like tides...
And to turn dc into ac, you need to rotate a small singularity around the pipes of electricity. That's why inverters are so heavy
Unless you have an electric car that can do vehicle to load. That means that you can plug in regular household devices like your fridge.
That vehicle isn’t using a traditional 12v car battery for that. Also the point t is you can’t connect a car battery to a fridge and expect it to work.
Unable to delete so editing instead. Leaving Lemmy.world due to privacy concerns.
Not with that attitude!
If a wire were a water stream:
Volt is water pressure (fast or slow stream)
Ampere how much water there is in the stream
Watt is pressure x amount
Ohm (resistance) is how much obstructions are in the stream
What a straightforward and clear way to put it, thank you kindly!
I never got the pipe analogy. Since liquid water can't be compressed, wouldn't the amperes be directly proportional to the volts and to the size of the pipe, assuming there are no air bubbles? Also, supposedly resistance only reduces current, but when I think of hair in a pipe, the pressure after the obstruction would also be lower (because pressure is directly proportional to the amount of water that flows)
Resistance in wire creates a voltage drop, just like hair in a water pipe creates a drop in available pressure.
Common misconception - it can, just not very much, so the volume change is tiny, and in practice, there's usually something else in the system that is changing volume by a larger amount- like air bubbles, or if there's anything elastic in the plumbing, it will stretch - but regardless, water absolutely can be under pressure.
You are correct, in electronics, resistance drops voltage (assuming the load is in series with the resistance). In fact, a cheap quick and dirty digital to analog converter uses a bunch of resistors to supply different voltages...
It would be. By ohm's law, I=V/R and R=V/I, so if V is fixed as V=1, then I=1/R, R=1/I, so it's is effectively the same thing, just measured in reverse.
He expressed it wrong. Amperes is diameter of the pipe, how much volume (or charge) can be transferred per unit of length at a given pressure; Watt is the amount of water flowing out at the end, which depends both on pressure and diameter.
Shouldn't it instead be the sum of the kinetic energy of all water molecules that come out the other end per unit of time (ie. total amount of energy you use move your volume of water with a certain pressure in a second)?
Yeah, that's not simple anymore then
A little more technical, I don't think your average starting battery is 100ah capacity, and most don't rate themselves in amp hours either.
I bought a deep cycle for my little sailboat at the local auto store and it's around 70-80ah
You would need an inverter to convert the batteries DC (direct current) into AC (alternating current). This will "cost" some power (watts) to convert that voltage. Your refrigerator runs on AC battery outputs DC.
That said, it is quite common to run refrigerators on larger boats and RVs off batteries and it would certainly be possible to run your house fridge off a single car battery for a short while if you've got an inverter large enough to run it.
What your not gonna do is just run out to the car, grab your battery and hook it directly to your fridge.
Our fridge uses between 130-180 watts when running and about 2.9Kw or 2900 watts in 24 hours. Your battery most likely has under 1000 total watt hours til empty, and car batteries are generally not used past 50% capacity (lead acid starting battery). So figure 500 watt hours max (for easy math). So... 4h run time maybe.
In your last paragraph, most of the places you write watts you mean watt hours. Good reminder that Wh is a bad unit, since it's too easy to confuse with watts.
Good catch... It was early and I was on my phone (my excuses) :)
It's just the 2.9kw should be kWh. Everything else is close enough.
While it's true that it won't be at max capacity, I will say that batteries these days will rate themselves in amp hours. For instance usually an 800 CCA AGM battery lists itself online as 7.5 AH.
The conversion process involves using the formula CCA = 7.2 x Ah to convert from Ah to CCA, and Ah = CCA / 7.2 to convert from CCA to Ah.
I specifically looked at the available specs at the local auto parts stores and couldn't find Ah details. This was about 2y ago, so maybe this value is becoming more commonplace. I know in the RV/Sailing works Ah is used pretty exclusively. My deep cycle AGM only lists CCA and reserve capacity
It's being answered authoritatively by an insurance agent.
I mean, the running on watts vs volts part was nonsense.
But, did get quite close with the power calculation. Although here in the UK the average car battery seems to be around 60ah. I did see some very expensive large 105ah batteries. But they were definitely the outlier. So if you had a 100ah battery then it would be 1.2kwh with 100% efficiency.
Also, it doesn't mention that you'd need an inverter to make the fridge run from a battery. These also have inefficiencies which would reduce the runtime on the battery.
Was about to say inverter until I saw your comment. I think the robot meant to call out AC vs DC.