Calculate ah's from wh's? Amp hours watt hours.
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PattySprinter
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I am just learning about this - from my notes: A x V = W ... ... ...
So, I would think that W/V = A
... but I was just reading today that there is a difference between A and Ah ... need more coffee ... feels like a rabbit hole lol!!
So, I would think that W/V = A
... but I was just reading today that there is a difference between A and Ah ... need more coffee ... feels like a rabbit hole lol!!
Optimistic Paranoid
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PattySprinter said:
Just like there is a difference between miles and miles per hour. Two different things, really.
Amps is a measure of how much current is flowing in a circuit at any particular instant. Amp hours is a way of measuring how much power a battery can deliver. A battery with 100 amp hours can provide 100 amps of current for 1 hour, or 50 amps for 2 hours, or 1 amp for 100 hours, etc.
In Sternwakian terms, that's a little oversimplified, but it's close enough to understand the principle.
Optimistic Paranoid
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Wabbit said:
That's correct.
100 amp hour battery was tested at a 5 amp, steady draw, for 20 hours. If the drain is 50 amps, the same battery will last a shorter time than 1/2 the hours (10 hrs). The battery puts up more internal resistance at higher ampere rates. It could be as little as 7 hours. Depending on the battery.
Divide the AH rating by the hours tested, should be 20 hours in a standard test. That gives you the tested ampere draw. You can use half of that.
Divide the AH rating by the hours tested, should be 20 hours in a standard test. That gives you the tested ampere draw. You can use half of that.
Spaceman Spiff
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PattySprinter said:
Amps is a unit of volume (how many electrons I have available), amp hours is a unit of flow rate (how fast am I using electrons).
A simple analogy is water: if you have 100 gallons (volume) you can take 1 gallon an hour for 100 hours or 10 gallons an hour for 10 hours (flow rate).
Amp hours = Watt hours ÷ Volts
-- Spiff
Trebor English
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Spaceman Spiff said:
It is reverse of that. One amp is a flow rate of one Coulomb per second. One Coulomb is a charge of 6.242×10^18 electrons. One amp hour is 60x60 or 3600 Coulombs.
While we are getting all technical and such, here are some interesting tidbits you can drop at the campfire.
How fast on average do electrons move through a copper wire?
About an inch every 100 seconds in the direction opposite that of positive current (Ben Franklin flipped a coin and got it backwards).
Why then does a light turn on nearly instantly at the end of a 20 foot electric cord when you apply a voltage source to the other end?
Because a wave propagates at nearly the speed of light down the wires. It causes the free electrons in the copper wire right next to the light bulb filament to start drifting at their inch per 100 seconds and the collisions within the filament cause it to heat up and glow. The electrons at the voltage source (battery, whatever) might not even reach the light bulb filament before you turn it off again.
Maybe not a good fireside conversation. They might toss you in to shut you up.
How fast on average do electrons move through a copper wire?
About an inch every 100 seconds in the direction opposite that of positive current (Ben Franklin flipped a coin and got it backwards).
Why then does a light turn on nearly instantly at the end of a 20 foot electric cord when you apply a voltage source to the other end?
Because a wave propagates at nearly the speed of light down the wires. It causes the free electrons in the copper wire right next to the light bulb filament to start drifting at their inch per 100 seconds and the collisions within the filament cause it to heat up and glow. The electrons at the voltage source (battery, whatever) might not even reach the light bulb filament before you turn it off again.
Maybe not a good fireside conversation. They might toss you in to shut you up.
IGBT said:
(This might be considered off-topic...so bear with us)
It also depends on voltage (EMF) and amount of current involved...and on an AC circuit, the electrons don't actually travel anywhere, they just dance back and forth, probably a few microns of travel in each direction.
If the actual electrons could move at the speed of light thru a conductor, (as in a particle accelerator vacuum) any living thing nearby would get large doses of X-rays and gamma rays...so of course this can't and doesn't happen in the normal world of electricity and wiring.
Electricity (EMF) thru conductors travels at close to the speed of light, but the electrons themselves move pretty slowly.
In electronics, things get complicated in a hurry. I'll try to illustrate a VERY basic principle:
Imagine that a multilane highway was a piece of wire, and the cars traveling along the highway are the 'amps'.
Also imagine that this highway is say, 6 lanes in one direction, and we have a solid line painted across the six lanes to help us do some measuring.
If there are cars occupying 4 of those lanes, running bumper to bumper, and side by side, at say, 50mph, then at any instant, if you look across the line of paint, we have a flow of four cars. That's a flow of four cars, or four amps. There is no final quantity we can see yet, just a flow of four cars (amps).
A steady flow of FOUR cars. That equates here to a flow of 4 amps thru a wire.
Now, in one hour, lets say we had 1000 cars pass by...(they were moving pretty fast!)
Now we can say we have a flow rate of 1000 car-hours, or amp-hours.
Lets imagine that the source of the flow of cars was a huge parking lot with 10,000 cars. This will be analogous to a battery.
So, at the end of 10 hours, all 10,000 cars will have passed the mark, and that's the end of the flow.
So our imaginary parking lot (battery) will be depleted in 10 hours. That's how long it took for 10,000 cars at 1000 cars per hour passing the mark we made.
Change the numbers to a 2 car flow past the line, and now it will take 20 hours to empty the parking lot, since we now have a flow of 2 cars, and a flow rate of 500 car-hours.
This is highly simplified but maybe it will help just a bit to visualize what the difference is between amps and amp-hours.
Imagine that a multilane highway was a piece of wire, and the cars traveling along the highway are the 'amps'.
Also imagine that this highway is say, 6 lanes in one direction, and we have a solid line painted across the six lanes to help us do some measuring.
If there are cars occupying 4 of those lanes, running bumper to bumper, and side by side, at say, 50mph, then at any instant, if you look across the line of paint, we have a flow of four cars. That's a flow of four cars, or four amps. There is no final quantity we can see yet, just a flow of four cars (amps).
A steady flow of FOUR cars. That equates here to a flow of 4 amps thru a wire.
Now, in one hour, lets say we had 1000 cars pass by...(they were moving pretty fast!)
Now we can say we have a flow rate of 1000 car-hours, or amp-hours.
Lets imagine that the source of the flow of cars was a huge parking lot with 10,000 cars. This will be analogous to a battery.
So, at the end of 10 hours, all 10,000 cars will have passed the mark, and that's the end of the flow.
So our imaginary parking lot (battery) will be depleted in 10 hours. That's how long it took for 10,000 cars at 1000 cars per hour passing the mark we made.
Change the numbers to a 2 car flow past the line, and now it will take 20 hours to empty the parking lot, since we now have a flow of 2 cars, and a flow rate of 500 car-hours.
This is highly simplified but maybe it will help just a bit to visualize what the difference is between amps and amp-hours.
Trebor English
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Ben Franklin was a smart guy. He affected my life by inventing bifocal glasses. Nicola Tesla invented the AC induction motor but that wouldn't have worked except Franklin had already invented electricity. I'm glad those guys came before me. : )
Andre-Marie Ampere invented the amp. Can you imagine surviving 8th grade with a name like that? They didn't have bathroom laws back then.
Andre-Marie Ampere invented the amp. Can you imagine surviving 8th grade with a name like that? They didn't have bathroom laws back then.
IGBT said:And when there is road construction on that highway and traffic is confined to one lane, that is a resistor.
Perfect!
I didnt think of that but I was typing it out after midnite...
It is admittedly very simple, and not exactly a perfect analogy...but I think it's close enuff to help illustrate what is going on with those pesky little amps...
Its kinda funny that amps are a flow based on a flow rate (coulombs)...but are not really a flow rate.
So amp-hours are a flow rate, based on a flow rate that is not really considered a flow rate.
Go figure.
I thought of a macro real world example that might further illustrate waves and electrons.
Think of a piece of driftwood in the middle of a calm lake. It is lazy meandering but mostly just floating on the flat water. Look to the distance and see an identical piece of driftwood near the shore, also just idling on the flat water.
All of a sudden a jetski zooms by and interrupts your peaceful pondering.
The wave generated by this annoying machine causes the driftwood near it at the center of the lake to start oscillating up and down. Much faster than any current or wind, the wave propagates toward the shore and the other piece of driftwood. Soon that piece of driftwood starts oscillating up and down.
The two pieces of driftwood never really moved horizontally across the lake and they never touched each other yet energy was transferred to the piece of wood at the shore (it takes energy to move the wood up against gravity).
Waves in lakes travel slow enough that we can visualize them while electromagnetic waves in wires travel near the speed of light so they are a bit hard to see. The electrons are still getting sloshed around though without physically changing position along the wire, just like the driftwood pieces on the lake.
That is about the best I can do.
Think of a piece of driftwood in the middle of a calm lake. It is lazy meandering but mostly just floating on the flat water. Look to the distance and see an identical piece of driftwood near the shore, also just idling on the flat water.
All of a sudden a jetski zooms by and interrupts your peaceful pondering.
The wave generated by this annoying machine causes the driftwood near it at the center of the lake to start oscillating up and down. Much faster than any current or wind, the wave propagates toward the shore and the other piece of driftwood. Soon that piece of driftwood starts oscillating up and down.
The two pieces of driftwood never really moved horizontally across the lake and they never touched each other yet energy was transferred to the piece of wood at the shore (it takes energy to move the wood up against gravity).
Waves in lakes travel slow enough that we can visualize them while electromagnetic waves in wires travel near the speed of light so they are a bit hard to see. The electrons are still getting sloshed around though without physically changing position along the wire, just like the driftwood pieces on the lake.
That is about the best I can do.
user 37446
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Reading all this about amps and amp hours, waves and electron flows, positive and negative, reminds me that it's still a "theory of electricity", meaning for dumb a$$ people like me, it's not a "law" yet, like gravity... :idea:
If it was a law then I'd have to try and understand it, being only a theory allows me to just shrug my shoulders and say "I dunno' but it works when I plug it in..."
If it was a law then I'd have to try and understand it, being only a theory allows me to just shrug my shoulders and say "I dunno' but it works when I plug it in..."
Optimistic Paranoid
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This world isn said:If it was a law then I'd have to try and understand it, being only a theory allows me to just shrug my shoulders and say "I dunno' but it works when I plug it in..."
But then how are you going to impress people with you scintillating conversation at cocktail parties?
This world isn said:Reading all this about amps and amp hours, waves and electron flows, positive and negative, reminds me that it's still a "theory of electricity", meaning for dumb a$$ people like me, it's not a "law" yet, like gravity... :idea:
If it was a law then I'd have to try and understand it, being only a theory allows me to just shrug my shoulders and say "I dunno' but it works when I plug it in..."
Wait...you never heard of Ohm's Law?
It's not just a good idea...its the LAW.
