Charged cell phone battery heavier than when drained?

[Fat Mac]

Yes it's psychological, the mass difference is incomprehensible to our dumb human brains.

IF we could feel that small of a weight change. we would probably be able to feel microscopic bugs n shit on our bodies all the time. PASS

[Hammerfest]

Nah, just you lying.

I'm sure if we gave you a charged battery and a drained one and asked you to figure out which is which by just weight in your hand, you'd be wrong 50% of the time.

What a charming thing to say.

[medievalman1]

Nah, just you lying.

I'm sure if we gave you a charged battery and a drained one and asked you to figure out which is which by just weight in your hand, you'd be wrong 50% of the time.

So hostile, so accusatory. If you gave him two batteries and told him one was charged and the other was not (without necessarily tell the truth), he'd probably think the charged one weight more.

[Turtel]

Perhaps when your phone is fully drained, you've been carrying it all day and have become accustomed to the weight, so you don't really notice it anymore. However, when the phone is fully charged, you've typically left it sitting on some bench (or some other surface) for several hours, so haven't become accustomed to the weight yet and when you go to pick it up it 'feels' heavier.

[Hammerfest]

Perhaps when your phone is fully drained, you've been carrying it all day and have become accustomed to the weight, so you don't really notice it anymore. However, when the phone is fully charged, you've typically left it sitting on some bench (or some other surface) for several hours, so haven't become accustomed to the weight yet and when you go to pick it up it 'feels' heavier.

No, because my phone tends to stay in my coat pocket. I only pull it out when I use it to text or call. I'm fully prepared to accept that it's all in my head, but I really don't think so so far. I'm not the only one who notices a weight change like this.

[Turtel]

No, because my phone tends to stay in my coat pocket. I only pull it out when I use it to text or call. I'm fully prepared to accept that it's all in my head, but I really don't think so so far. I'm not the only one who notices a weight change like this.

There's definitely a psychological component to an object's perceived weight. There's this one trick involving three card boxes where people are first made to pick up one box of cards a few times, to become accustomed to that weight, then two extra empty boxes of cards are placed on top of the original box which the participants are then asked to pick up all together. People will perceive that picking up the three boxes felt lighter than picking up just the one box of cards when in fact the three boxes were slightly heavier than just the one box. The trick works because people have gotten used to picking up the one box of cards, and expect the three boxes of cards to be harder to pick up, when in reality they both (one box vs three boxes) have a similar weight.

Here's a video showing the trick in action:

[chazus]

What a charming thing to say.

It was a bit rude but... he's not wrong. The thing is, you don't KNOW how much charge your battery has. Not without turning it on and looking at it.

If you plugged your phone in for a day, and didn't realize that that cable was broken and was delivering no power, and then went about your day, you'd think your phone was heavier.

Alternatively, if you accidentally left your screen on, face down, and picked it up after leaving it at a full charge, you'd probably think it was heavier, because you think it has a full charge.

I'm not the only one who notices a weight change like this.

A) You are the only one who notices the change
B) A is false, because there isn't, and you don't. It's entirely psychological.

That said, you're probably not the only person who THINKS theres a weight change.

[Mormolyce]

If only science had devised some kind of instrument to measure weight.

[Ravenblade]

One single electron weighs about 9.12 x 10 ^ -33 grams and contains a charge of 1.062 x 10 ^ -19 C (A x s). So if your battery can hold about 2500 mAh or 0.694 mAs or 0.000694 As you know that you require about 6.5 quadrillian electrons, so your phone will weigh about 1.255 x 10 ^ -17 grams more (or like about 126 femtograms more). You will definitely feel the weight pulling on you.

[Forogil]

One single electron weighs about 9.12 x 10 ^ -33 grams and contains a charge of 1.062 x 10 ^ -19 C (A x s). So if your battery can hold about 2500 mAh or 0.694 mAs or 0.000694 As you know that you require about 6.5 quadrillian electrons, so your phone will weigh about 1.255 x 10 ^ -17 grams more (or like about 126 femtograms more). You will definitely feel the weight pulling on you.

Wrong calculation giving almost the right result.
OOPS wrong by a factor 1000, forgot to account for SI using kg not g as base-unit.

"Charging" does not make it hold more electrons - it just moves them from one part of the battery to another (part as in logical part; there is no major dipole moment either).

In terms of energy that "charge" of 2500mAh will need to be multiplied by the voltage (about 1.2V) to give the energy - and then divided by c^2 due to m=E/c^2 - giving about 120pg.

[Hammerfest]

It was a bit rude but... he's not wrong.

He accused me of lying. That was wrong.

[bigsav1]

Obviously we're not telling him which is which..

Seems like that post went over your head.

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It's wrong to accuse people of flying? Since when? Do you want a safe space?

My point was that you can't actually tell and if we tested your belief that you could, you'd be wrong 50% of the time because you'd be guessing. It'd be like flipping a coin.

Or can you tell which side a coin will land after flipping it too?

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I doubt most people have a mass spectrometer lying around.

Or just give him 2 dead batteries and tell him one has a full charge and see if he really can tell the difference. I'm gonna go with probably not.

[Turtel]

Wrong calculation giving almost the right result.
OOPS wrong by a factor 1000, forgot to account for SI using kg not g as base-unit.

"Charging" does not make it hold more electrons - it just moves them from one part of the battery to another (part as in logical part; there is no major dipole moment either).

In terms of energy that "charge" of 2500mAh will need to be multiplied by the voltage (about 1.2V) to give the energy - and then divided by c^2 due to m=E/c^2 - giving about 120pg.

Based on the stats of the iPhone 4S battery (5.3 Wh = 19100 J) I calculate the mass equivalence of the energy at full charge to be 2.13*10^-13 kg which would be about 17 million times the mass that Ravenblade calculated. Which is interesting, since it suggests that the actual mass of the electrons contributes significantly less to the overall mass of the system than the mass equivalence of the energy of the configuration of the electrons. However, if we're going to be pedantic enough to include the mass equivalence of the energy gained by moving electrons, then we should also consider other factors that would change the weight of the phone as well.

Apparently, at a high charge, pouch-type lithium ion batteries (which most mobile phones use) expand in size due to the vaporization of the electrolyte. This effect is significant enough that it can cause delamination of the layers, destroying the battery (and inflating it to about double the size as seen in this image). As we might know, increasing the size of an object will increase the buoyant force of air acting on the object, and if there is no corresponding increase in mass, then the object would feel lighter. This would normally be considered minuscule and insignificant, but relative to the mass of the energy gained from charging a phone battery, it's potentially huge.

Let's just assume that at full charge the vaporasation of the electrolyte results in the battery expanding by 1/10000 (0.01%), a completely unnoticable change to the human eye. Using the dimensions of the iPhone 4S battery (4.54 x 2.31 x 0.13 inches) I calculate the battery to have a volume of 2.234*10-5 m^3, which means if the battery expands by 0.01% the volume would increase by 2.234*10^-9 m^3. Air has a density of 1.225 kg/m^3. This means the increase in the buoyant force of air acting on the battery is equivalent to the weight of a mass of 2.234*10^-9*1.225 = 2.74*10^-9 kg.

This is about 12900 times larger than the mass of the energy gained by charging the phone. In other words, the battery should feel lighter when it's fully charged, when considering just these two factors. There would of course be other factors that introduce variability in the weight of the phone as well, such as dust/dirt getting trapped in the crevices of the phone or perhaps microscopic flakes of material being scratched off the phone each time it gets charged/used.

[mickybrighteyes]

Hmmm... why is it impossible for me to notice?

the things which are carrying the weight are carrying such small amoutns of weight that we can't really tell the difference thus it's apparently no change in weight unless you have some ridiculously precise tools.

[Mormolyce]

I doubt most people have a mass spectrometer lying around.

That's not what a... wait was that a joke?

[Forogil]

Based on the stats of the iPhone 4S battery (5.3 Wh = 19100 J) I calculate the mass equivalence of the energy at full charge to be 2.13*10^-13 kg which would be about 17 million times the mass that Ravenblade calculated.

Looking more it seems there are two different numbers: 1.2e-17g and 1.2e-13g (a femtogram is 1e-15g).

Let's just assume that at full charge the vaporasation of the electrolyte results in the battery expanding by 1/10000 (0.01%), a completely unnoticable change to the human eye. Using the dimensions of the iPhone 4S battery (4.54 x 2.31 x 0.13 inches) I calculate the battery to have a volume of 2.234*10-5 m^3, which means if the battery expands by 0.01% the volume would increase by 2.234*10^-9 m^3. Air has a density of 1.225 kg/m^3. This means the increase in the buoyant force of air acting on the battery is equivalent to the weight of a mass of 2.234*10^-9*1.225 = 2.74*10^-9 kg.

Ah, nice, but I thought that the problem is that it doesn't shrink back afterwards causing old batteries to fatten.

Thus it doesn't become heavier when drained, but lighter when charged :-)
(I would expect that thermal expansion when draining the battery will also add something of almost similar nature.)

[Deleted]

I have noticed for several years that my various cell phones feel slightly heavier when on a full charge than when they are completely drained. I lack the tools at the moment to weigh the phone to see if I'm right. Does anyone else feel the same thing?

It's heavier cause of the good old E=mc2 but since the charge in those batteries are tiny compared to their overall weight, you can't possibly notice it without very sensitive instruments.

[Jester Joe]

probably. i dont doubt you feel its heavier. i had to google it myself.


kind of like when i think my phone is vibrating in my pocket but its sitting on the table. what up with that?

And they said video games wouldn't teach me anything! Thanks, Persona 5!

TL;DR- It's actually a mental thing.

[Speaker]

Hmmm... why is it impossible for me to notice?

Placebo, it's all in your head.

[Thoughtful Trolli]

There doesn't seem to be a debate about whether or not it's heavier, but it's very sad to see so many people with senses that are too retarded to detect the actual change in mass.

Placebo, it's all in your head.

That "placebo" is actually the start of extra sensory perceptions. It doesn't matter how he knows or not, his brain is advanced enough to collect data even his ego isn't aware of having collected.

Shame on you for trying to destroy another potentially gifted life! You're the humanoid equivalent of overpushed vaccinations!