# Weight difference between fully charged and discharged phone
**URL:** https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319
**Category:** Factual Questions
**Created:** [July 26, 2021, 11:49am UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319 "2021-07-26T11:49:30Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Nansbread1](https://boards.straightdope.com/u/Nansbread1)
#### Post date: [July 26, 2021, 11:49am UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/1 "2021-07-26T11:49:30Z")
So what is the difference in weight between full and empty battery in mobile phones. Can that be used as a measure for weight of energy? If not why not.
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### Author:  [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)
#### Post date: [July 26, 2021, 12:11pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/2 "2021-07-26T12:11:10Z")
A charged battery weighs more than a depleted battery. But the difference is so small that it would be impossible to measure using current technology.
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### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [July 26, 2021, 12:22pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/3 "2021-07-26T12:22:03Z")
Take an iPhone 12 battery, supposedly 2815 mAh at 3.83 V. That’s 10.78 Wh which is 38808 J. Plug that into E=mc^2 and you get 4.318\*10^-13 kg, or less than half a picogram. There’s a lot of things other than the charge state that can make the battery weight change that much.
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### Author:  [@gnoitall](https://boards.straightdope.com/u/gnoitall)
#### Post date: [July 26, 2021, 8:58pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/4 "2021-07-26T20:58:04Z")
A lithium ion battery is an energy storage medium, not an energy creation device. In theory, the chemical reaction that creates the electric current during discharge is perfectly reversible during charging. A charged battery gains no more mass during charging than a tightly wound rubber band gains mass during winding.
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### Author:  [@pulykamell](https://boards.straightdope.com/u/pulykamell)
#### Post date: [July 26, 2021, 10:37pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/5 "2021-07-26T22:37:07Z")
> [@Crafter\_Man](#):
>
> But the difference is so small that it would be impossible to measure using current technology.
How about using voltage technology?
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### Author:  [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)
#### Post date: [July 26, 2021, 11:58pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/6 "2021-07-26T23:58:23Z")
> [@naita](#):
>
> less than half a picogram.
Just for comparison, a speck of dust weighs 160,000 picograms.
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### Author:  [@mixdenny](https://boards.straightdope.com/u/mixdenny)
#### Post date: [July 27, 2021, 2:15am UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/7 "2021-07-27T02:15:56Z")
> [@CookingWithGas](#):
>
> Just for comparison, a speck of dust weighs 160,000 picograms.
This is why the SDMB rules. Now we’re cookin!
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### Author:  [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)
#### Post date: [July 27, 2021, 1:46pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/9 "2021-07-27T13:46:40Z")
> [@pulykamell](#):
>
> How about using voltage technology?
Please resist electricity puns.
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### Author:  [@pulykamell](https://boards.straightdope.com/u/pulykamell)
#### Post date: [July 27, 2021, 1:49pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/10 "2021-07-27T13:49:22Z")
Am I grounded?
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### Author:  [@mordecaiB](https://boards.straightdope.com/u/mordecaiB)
#### Post date: [July 27, 2021, 9:52pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/11 "2021-07-27T21:52:25Z")
> [@CookingWithGas](#):
>
> Just for comparison, a speck of dust weighs 160,000 picograms.
What if my speck of dust is bigger than your speck of dust?
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### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [July 27, 2021, 10:03pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/12 "2021-07-27T22:03:52Z")
> [@mordecaiB](#):
>
> What if my speck of dust is bigger than your speck of dust?
Then it weighs more.
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### Author:  [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)
#### Post date: [July 27, 2021, 10:23pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/13 "2021-07-27T22:23:46Z")
> [@naita](#):
>
> Then it weighs more.
Weighs more than what? A duck?
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### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [July 27, 2021, 10:25pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/14 "2021-07-27T22:25:49Z")
> [@abcdefghij](#):
>
> Weighs more than what? A duck?
The smaller speck of dust.
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### Author:  [@wolfpup](https://boards.straightdope.com/u/wolfpup)
#### Post date: [July 27, 2021, 10:26pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/15 "2021-07-27T22:26:39Z")
> [@gnoitall](#):
>
> A lithium ion battery is an energy storage medium, not an energy creation device. In theory, the chemical reaction that creates the electric current during discharge is perfectly reversible during charging. A charged battery gains no more mass during charging than a tightly wound rubber band gains mass during winding.
A battery is indeed just an energy storage medium, but the energy it gains when it charges comes from an external source, and the energy it loses when it discharges is dispersed externally in the form of heat and/or EM radiation. Both a charged battery and a tightly-wound elastic weigh more than a discharged battery and an unwound elastic, because the mass-energy equivalence of E=mc2 is an inviolable fact of nature. It’s just that the mass difference is so incredibly small it’s meaningless in everyday experience.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [July 27, 2021, 11:35pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/16 "2021-07-27T23:35:45Z")
Why a duck?
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### Author:  [@MonkeysBrother](https://boards.straightdope.com/u/MonkeysBrother)
#### Post date: [July 27, 2021, 11:54pm UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/17 "2021-07-27T23:54:55Z")
Really? I am not a physicist, so I’m just asking. I get it that mass can be converted to energy and vice versa, but stretching the chemical bonds in that elastic or storing energy in chemical bonds in the battery adds mass? The input energy is certainly in a different form, but why/how is some of it converted to mass? If I lift a billiard ball two feet off the table (thus adding potential energy), does some of that energy I put in get converted to mass? Inquiring minds etc.
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### Author:  [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)
#### Post date: [July 28, 2021, 12:21am UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/18 "2021-07-28T00:21:23Z")
> [@Chronos](#):
>
> Why a duck?
To see if it’s made of wood
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### Author:  [@Voyager](https://boards.straightdope.com/u/Voyager)
#### Post date: [July 28, 2021, 12:24am UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/19 "2021-07-28T00:24:20Z")
> [@engineer\_comp\_geek](#):
>
> Please resist electricity puns.
Cecil should write a coulomb about this.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [July 28, 2021, 12:47am UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/20 "2021-07-28T00:47:44Z")
It’s not that “some of the energy is converted to mass”. It’s all mass, and never needed to be “converted”. In modern physics, “mass” is defined as “that portion of energy that a thing has even when its center is not moving”.
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### Author:  [@Melbourne](https://boards.straightdope.com/u/Melbourne)
#### Post date: [July 28, 2021, 2:30am UTC](https://boards.straightdope.com/t/weight-difference-between-fully-charged-and-discharged-phone/947319/21 "2021-07-28T02:30:55Z")
> [@Chronos](#):
>
> “that portion of energy that a thing has even when its center is not moving”.
Not an answer, begs the question “what is a thing”. Is a static electric field a thing?
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