Are charged batteries heavier than dead ones?

[JoeDimwit]

Pretty sure the S.T.E.M. geeks got us here in the first place.

Let's give them their due, and a big bag of Cheezy-Poofs.??

You’ll get powdered cheese all over the interior!!! ???

Sponsored

 

[Blanked]

Pretty sure the S.T.E.M. geeks got us here in the first place.

Let's give them their due, and a big bag of Cheezy-Poofs.??

Mnt. DEW

 

[OH2AZ2OH]

Geek replying here: yes, a fully charged battery has more mass than a depleted battery, due to E=mc^2. It has *nothing* to due with consuming electrons though. This also applies to mechanical systems. If you have a mechanical watch, technically it has more mass (note: mass, not weight - I'll get back to that) than an unwound watch. As has been mentioned a couple of times, the difference in mass is much, much, much smaller than we have the ability to measure. Even pushing you vehicle up a hill increases your vehicle's potential energy, which increases its mass a tiny tiny tiny amount. But, being up a hill takes you farther away from the Earth's center of gravity, and the difference in gravitational strength is much larger than the difference in mass. So, your otherwise identical car ends up *weighing* less at the top of the hill even though it has more mass.

 

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[dml105]

Alright… let’s just go ahead and keep all the S.T.E.M. malarkey off my automobile forum. Kthanks. ?

Car forums are filled with discussions on how cars work. Carburetors, tire pressure, turbos, sound systems... all math and science. Sorry buddy, it was STEM all along! (I know you're kidding here though.)

Even pushing you vehicle up a hill increases your vehicle's potential energy, which increases its mass a tiny tiny tiny amount.

How, Sway?!

It's either mass or it's energy. It is not both. Taking a mass up a hill (adding potential energy) does not make the mass greater. It adds energy. (Sort of. It's really just a mathematical construct to simplify the effects of gravitation. If you take the mass high enough, you're outside the "linear" range of gravity, and your potential energy asymptotically drops to zero.)

Just like heating up a mass does not make the mass greater. It adds energy.

 

[OH2AZ2OH]

Because of E=mc^2. If a system has more energy, including electrical or potential or kinetic, it has more mass. Because the speed of light is so high, and it is squared, the amount of mass added is infinitesimal. We'll likely never be able to detect it, but that doesn't mean it isn't real. We do have scales that are sensitive enough to detect the change in weight at sea level vs on a mountain top, which is pretty remarkable.

 

[jgcom]

As I wait (and wait, and wait) for my Mach-E to arrive, I've been mostly just reading things in this forum, very appreciative to learn what to expect and look out for. I look forward to submitting dumb questions. I am a physicist, though, and can try explaining this topic. I did not attend Harvard, but earned a couple of degrees from an institute of technology a few miles down the Charles River. My specialty includes relativity, and I'm an experimentalist, used to thinking about what can be measured. For what it's worth, there are EVs and mustangs in my lab's parking lot, and mine will be the first in both categories.

Einstein's General Relativity (GR) theory, now about 105 years old, pre-dating most of what is now thought of as modern physics. GR was Einstein's successful attempt to reconcile what he had contributed connecting the physics of electromagetism and fast-moving objects (Special Relativity) with Newton's mathematical explanation of gravity. Even today, we know of no experimental or observational results that contradict General Relativity, despite all of the physics discovered in the last century!

GR's main conceptual leap was to realize that gravity is the result of curvature in spacetime, and that (unlike in Newton's theory) gravity doesn't change instantaneously across great distances. Instead, the local presence of matter and energy cause spacetime to curve, and then the spacetime's shape tells matter and energy how to move, determining how spacial and time coordinates are measured. Objects feel mutual gravitational attraction because of the curvature seen by each of them. The curvature changes can only propagate at the speed of light (this is not relevant to weighing Mach-E batteries.)

Think about that closed metal box that holds the car batteries. Let's assume for moment that the box is physically sealed and thermally isolated—though in reality neither is likely true. When charging, as has been pointed out, electrons do not accumulate in the box, but the chemical potential energy is increased in the cells. We don't need to know how energy is stored and don't even need to understand chemistry or atomic physics to say this: when the energy in the box increases, the (extremely small) spacetime curvature around it increases. This is the modern way of saying that the box's mass increases, both gravitational and intertial. E=mc^2 is a perfectly good way to estimate that, and the answer for an 88 kWh Mach-E battery charging from zero to 100% is a equivalent to 3.5 micrograms. That's not a lot, but it is real and would be easily measurable ... except:

- If the battery has vents, for example to prevent it from exploding, gas can come and go in quantities more than micrograms.
- If the battery's case deforms due to temperature changes or physical stresses from the charging cells, even a tiny bit, the change in buoyancy force could be more than micrograms.

It is an interesting question, at least to me!

 

[dml105]

As I wait (and wait, and wait) for my Mach-E to arrive, I've been mostly just reading things in this forum, very appreciative to learn what to expect and look out for. I look forward to submitting dumb questions. I am a physicist, though, and can try explaining this topic. I did not attend Harvard, but earned a couple of degrees from an institute of technology a few miles down the Charles River. My specialty includes relativity, and I'm an experimentalist, used to thinking about what can be measured. For what it's worth, there are EVs and mustangs in my lab's parking lot, and mine will be the first in both categories.

Einstein's General Relativity (GR) theory, now about 105 years old, pre-dating most of what is now thought of as modern physics. GR was Einstein's successful attempt to reconcile what he had contributed connecting the physics of electromagetism and fast-moving objects (Special Relativity) with Newton's mathematical explanation of gravity. Even today, we know of no experimental or observational results that contradict General Relativity, despite all of the physics discovered in the last century!

GR's main conceptual leap was to realize that gravity is the result of curvature in spacetime, and that (unlike in Newton's theory) gravity doesn't change instantaneously across great distances. Instead, the local presence of matter and energy cause spacetime to curve, and then the spacetime's shape tells matter and energy how to move, determining how spacial and time coordinates are measured. Objects feel mutual gravitational attraction because of the curvature seen by each of them. The curvature changes can only propagate at the speed of light (this is not relevant to weighing Mach-E batteries.)

Think about that closed metal box that holds the car batteries. Let's assume for moment that the box is physically sealed and thermally isolated—though in reality neither is likely true. When charging, as has been pointed out, electrons do not accumulate in the box, but the chemical potential energy is increased in the cells. We don't need to know how energy is stored and don't even need to understand chemistry or atomic physics to say this: when the energy in the box increases, the (extremely small) spacetime curvature around it increases. This is the modern way of saying that the box's mass increases, both gravitational and intertial. E=mc^2 is a perfectly good way to estimate that, and the answer for an 88 kWh Mach-E battery charging from zero to 100% is a equivalent to 3.5 micrograms. That's not a lot, but it is real and would be easily measurable ... except:

- If the battery has vents, for example to prevent it from exploding, gas can come and go in quantities more than micrograms.
- If the battery's case deforms due to temperature changes or physical stresses from the charging cells, even a tiny bit, the change in buoyancy force could be more than micrograms.

It is an interesting question, at least to me!

Nerd. ;-)

But this is why you ask a Course 8 person this question, and not a Course 6 person like me.

My physics friends have caused me to doubt my answer. Thanks for your contribution.

 

[timbop]

As I wait (and wait, and wait) for my Mach-E to arrive, I've been mostly just reading things in this forum, very appreciative to learn what to expect and look out for. I look forward to submitting dumb questions. I am a physicist, though, and can try explaining this topic. I did not attend Harvard, but earned a couple of degrees from an institute of technology a few miles down the Charles River. My specialty includes relativity, and I'm an experimentalist, used to thinking about what can be measured. For what it's worth, there are EVs and mustangs in my lab's parking lot, and mine will be the first in both categories.

Einstein's General Relativity (GR) theory, now about 105 years old, pre-dating most of what is now thought of as modern physics. GR was Einstein's successful attempt to reconcile what he had contributed connecting the physics of electromagetism and fast-moving objects (Special Relativity) with Newton's mathematical explanation of gravity. Even today, we know of no experimental or observational results that contradict General Relativity, despite all of the physics discovered in the last century!

GR's main conceptual leap was to realize that gravity is the result of curvature in spacetime, and that (unlike in Newton's theory) gravity doesn't change instantaneously across great distances. Instead, the local presence of matter and energy cause spacetime to curve, and then the spacetime's shape tells matter and energy how to move, determining how spacial and time coordinates are measured. Objects feel mutual gravitational attraction because of the curvature seen by each of them. The curvature changes can only propagate at the speed of light (this is not relevant to weighing Mach-E batteries.)

Think about that closed metal box that holds the car batteries. Let's assume for moment that the box is physically sealed and thermally isolated—though in reality neither is likely true. When charging, as has been pointed out, electrons do not accumulate in the box, but the chemical potential energy is increased in the cells. We don't need to know how energy is stored and don't even need to understand chemistry or atomic physics to say this: when the energy in the box increases, the (extremely small) spacetime curvature around it increases. This is the modern way of saying that the box's mass increases, both gravitational and intertial. E=mc^2 is a perfectly good way to estimate that, and the answer for an 88 kWh Mach-E battery charging from zero to 100% is a equivalent to 3.5 micrograms. That's not a lot, but it is real and would be easily measurable ... except:

- If the battery has vents, for example to prevent it from exploding, gas can come and go in quantities more than micrograms.
- If the battery's case deforms due to temperature changes or physical stresses from the charging cells, even a tiny bit, the change in buoyancy force could be more than micrograms.

It is an interesting question, at least to me!

Great explanation, and thanks for taking the time. However, in the context of a 5000 pound vehicle 3.5 micrograms could be considered statistically insignificant, particularly in relation to the weight of dirt on said vehicle having orders of magnitude more mass.

While a great mental exercise, saying the mass changes an extremely tiny amount is a distinction without a difference. I think the assumption being made at the outset is that somehow the electrons are "used" and thus "go somewhere" other than the car (ie expelled or consumed), which is incorrect. What is added during charging is potential energy, not additional electrons.

 

[Carsinmyblood]

As I wait (and wait, and wait) for my Mach-E to arrive, I've been mostly just reading things in this forum, very appreciative to learn what to expect and look out for. I look forward to submitting dumb questions. I am a physicist, though, and can try explaining this topic. I did not attend Harvard, but earned a couple of degrees from an institute of technology a few miles down the Charles River. My specialty includes relativity, and I'm an experimentalist, used to thinking about what can be measured. For what it's worth, there are EVs and mustangs in my lab's parking lot, and mine will be the first in both categories.

Einstein's General Relativity (GR) theory, now about 105 years old, pre-dating most of what is now thought of as modern physics. GR was Einstein's successful attempt to reconcile what he had contributed connecting the physics of electromagetism and fast-moving objects (Special Relativity) with Newton's mathematical explanation of gravity. Even today, we know of no experimental or observational results that contradict General Relativity, despite all of the physics discovered in the last century!

GR's main conceptual leap was to realize that gravity is the result of curvature in spacetime, and that (unlike in Newton's theory) gravity doesn't change instantaneously across great distances. Instead, the local presence of matter and energy cause spacetime to curve, and then the spacetime's shape tells matter and energy how to move, determining how spacial and time coordinates are measured. Objects feel mutual gravitational attraction because of the curvature seen by each of them. The curvature changes can only propagate at the speed of light (this is not relevant to weighing Mach-E batteries.)

Think about that closed metal box that holds the car batteries. Let's assume for moment that the box is physically sealed and thermally isolated—though in reality neither is likely true. When charging, as has been pointed out, electrons do not accumulate in the box, but the chemical potential energy is increased in the cells. We don't need to know how energy is stored and don't even need to understand chemistry or atomic physics to say this: when the energy in the box increases, the (extremely small) spacetime curvature around it increases. This is the modern way of saying that the box's mass increases, both gravitational and intertial. E=mc^2 is a perfectly good way to estimate that, and the answer for an 88 kWh Mach-E battery charging from zero to 100% is a equivalent to 3.5 micrograms. That's not a lot, but it is real and would be easily measurable ... except:

- If the battery has vents, for example to prevent it from exploding, gas can come and go in quantities more than micrograms.
- If the battery's case deforms due to temperature changes or physical stresses from the charging cells, even a tiny bit, the change in buoyancy force could be more than micrograms.

It is an interesting question, at least to me!

So in other words we're just a few electrons from warp drive.

I KNEW IT. I knew we'd be there some day.

 

[Carsinmyblood]

As I wait (and wait, and wait) for my Mach-E to arrive, I've been mostly just reading things in this forum, very ...... It is an interesting question, at least to me!

Just to the left of this topic, I think you'll get a kick out of this: My grandfather corresponded with scientists in Germany before WWII. He was growing (pulling) Germanium crystal in his basement lab. After the war he was discovered (not hard, he lived half a mile away) and hired by Bell Labs in Murray Hill. (You can see where this is going) He and some of his German buddies were gathered up and were on the team that grew the crystal for the first transistor and before he died some of the first IC chips. I have his commemorative working copy that was made on the 40th anniversary, made sometime in the 80's IIRC. I have 5 family members who worked there including my father in law who worked on Telstar. His name, along with everyone else's is on the chassis. There's a flight-ready model in the Bell Labs, Murray Hill museum on the property.

Sitting next to it is a large scale array of transistors for comparison, boasting 800 thousand in a square inch.

 

[DBC]

Some batteries will get heavier during discharge. For example, a lithium air battery adds oxygen to the lithium at the positive electrode during discharge. That would not be an insignificant difference. Obviously not relevant for current commercial batteries.

 

[Murse-In-Airy]

I told a friend about the impending Mach E purchase and the discussion turned to electric planes and eventual passenger jets without the jets, of course.

He said something that I couldn't dispute. He said batteries get lighter as they discharge. I didn't want to appear un or misinformed.

So, DO batteries change their weight? Even slightly?

Turns out he was right. It's almost immeasurable though, so put away your bathroom scales. Mathematically, energy has mass. Learned something new today.

https://physics.stackexchange.com/q...s-of-a-battery-change-when-charged-discharged

Skipping over all the mathematical and theoretical arguments between the original post and here. Because all I want to say is Thanks for sharing. I learned something. That makes three things today. I’m on a roll. Better go take a nap before I overdo it.

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