# Do batteries get heavier when you charge them? **URL:** \ **Category:** Factual Questions\ **Created:** [March 29, 2011, 3:40am UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345 "2011-03-29T03:40:18Z")\ **Posts on this page:** 14\ **Page:** 3
**Author:** ![glowacks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/glowacks/32/5548_2.png) [@glowacks](https://boards.straightdope.com/u/glowacks)\ **Post date:** [March 30, 2011, 2:25am UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/41 "2011-03-30T02:25:48Z")
> [@automagic](#): > > Please correct me if I’m wrong but I believe that photons are massless, otherwise they would have infinite weight since they travel at the speed of light. All energy has mass. When folks talk about the energy released from a nuclear reaction, they are talking about energy that was beforehand able to be measured on a scale because it was confined to the nucleus of an atom; that energy was in a sense holding the nucleus together (but don’t take it all that literally). When the nucleus changes, the resulting particles appear to have less mass, but if you were somehow able to contain all the products in a closed system the system’s mass would not change; the mass would be less confined, but still there. Einstein’s famous equation in its basic form tells you how much mass energy has. The amount of energy a single photon has can be transformed to zero\*: by traveling nearly as fast as the photon directly away from it. In doing so the photon’s wavelength increases due to (relativistic) Doppler effect and thus loses energy as a photon’s energy is inversely proportional to its wavelength. If you have two photons going in exact opposite directions though, there would be a corresponding increase in energy in the other photon. I don’t know how the mathematics behind it works out, just the vague description, but in such a system there is, in some sense, a well-defined positive invariant mass even though it is composed of particles that taken separately have zero invariant mass. It is probably drastically oversimplified, but it’s how I’ve come to understand the nature of it. \*To be precise, can be transformed to be less than any given positive number. When that happens, we can pretend it actually can go to zero even though such a situation would require moving at the speed of light. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [March 30, 2011, 3:24am UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/42 "2011-03-30T03:24:57Z")
Go read your link. ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [March 30, 2011, 3:48am UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/43 "2011-03-30T03:48:17Z")
> [@thelabdude](#): > > Go read your link. Both **Pasta** and **Chronos** are honest to God physicists. Believe me, they know of which they speak. Although **Pasta** has some trouble defining mass. (Just kidding) ---
**Author:** ![Mosier](https://avatars.discourse-cdn.com/v4/letter/m/7ea924/32.png) [@Mosier](https://boards.straightdope.com/u/Mosier)\ **Post date:** [March 30, 2011, 4:40am UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/44 "2011-03-30T04:40:32Z")
> [@thelabdude](#): > > The conservation of matter in chemical reaction is absolute. There isn’t even a small change in mass. The only way the mass of a battery will change is if it gains or loses material. Fire is a chemical reaction, right? I’m 99% sure my great grandmother weighed more before her cremation than afterward… ---
**Author:** ![Son\_of\_a\_Rich](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/son_of_a_rich/32/5439_2.png) [@Son\_of\_a\_Rich](https://boards.straightdope.com/u/Son_of_a_Rich)\ **Post date:** [March 30, 2011, 4:45am UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/45 "2011-03-30T04:45:01Z")
> [@Snnipe\_70E](#): > > So if I carry a lead weight up from the street level to the top of a 15 story building and hold it over the edge of the building its mass will increase because its potential energy has increased? It will if you live in New Crobuzon. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [March 30, 2011, 4:50am UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/46 "2011-03-30T04:50:06Z")
> [@Ring](#): > > Although **Pasta** has some trouble defining mass. (Just kidding) Ahem… 😉 ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 30, 2011, 4:52pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/47 "2011-03-30T16:52:53Z")
> [@](#): > > Fire is a chemical reaction, right? I’m 99% sure my great grandmother weighed more before her cremation than afterward… Not if you measured _all_ of the remains. Most of her didn’t go home in the little urn; it went up the flue at the crematorium. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [March 30, 2011, 5:38pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/48 "2011-03-30T17:38:45Z")
> [@Chronos](#): > > Not if you measured _all_ of the remains. Most of her didn’t go home in the little urn; it went up the flue at the crematorium. And the smoke will actually weigh more since it’s combined with oxygen. This discovery was one of the key findings to move us toward modern chemistry. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 30, 2011, 5:44pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/49 "2011-03-30T17:44:28Z")
> [@thelabdude](#): > > The conservation of matter in chemical reaction is absolute. There isn’t even a small change in mass. The only way the mass of a battery will change is if it gains or loses material. > [@Mosier](#): > > Fire is a chemical reaction, right? I’m 99% sure my great grandmother weighed more before her cremation than afterward… > [@Chronos](#): > > Not if you measured _all_ of the remains. Most of her didn’t go home in the little urn; it went up the flue at the crematorium. and all the fuel and oxygen input. do they make really huge bell jars? ---
**Author:** ![JoelUpchurch](https://avatars.discourse-cdn.com/v4/letter/j/f05b48/32.png) [@JoelUpchurch](https://boards.straightdope.com/u/JoelUpchurch)\ **Post date:** [March 31, 2011, 2:45pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/50 "2011-03-31T14:45:34Z")
Some of the new battery chemistries like the lithium-air battery should actually get **lighter** when you charge them, since the chemical reaction that generates electricity involves combining lithium with atmospheric oxygen, which would mean the battery would get heavier as it discharged. [http://en.wikipedia.org/wiki/Lithium\_air\_battery](http://en.wikipedia.org/wiki/Lithium_air_battery) ---
**Author:** ![glilly](https://avatars.discourse-cdn.com/v4/letter/g/48db29/32.png) [@glilly](https://boards.straightdope.com/u/glilly)\ **Post date:** [March 31, 2011, 3:15pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/51 "2011-03-31T15:15:57Z")
Wouldn’t this then also apply to standard chemical reactions, exothermic reducing mass and endothermic increasing? Or for that matter, any material changing temperature? I think the problem for us who aren’t as deep into physics, we understand the conversion of mass to energy in a nuclear reaction due to the change in atomic weight. But this idea that additional energy adds mass without a change to the atomic structure is foreign. It means the energy has mass without being converted to a thing (like a particle). That’s something I wasn’t taught in basic physics class. Or it was and I forgot. ---
**Author:** ![Alka\_Seltzer](https://avatars.discourse-cdn.com/v4/letter/a/c89c15/32.png) [@Alka\_Seltzer](https://boards.straightdope.com/u/Alka_Seltzer)\ **Post date:** [March 31, 2011, 4:28pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/52 "2011-03-31T16:28:27Z")
I get heavier when I eat batteries. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 31, 2011, 7:15pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/53 "2011-03-31T19:15:22Z")
> [@](#): > > I think the problem for us who aren’t as deep into physics, we understand the conversion of mass to energy in a nuclear reaction due to the change in atomic weight. But this idea that additional energy adds mass without a change to the atomic structure is foreign. It means the energy has mass without being converted to a thing (like a particle). The energy isn’t converted into new particles (or at least, not _real_ particles) in a nuclear reaction, either. The number of protons and neutrons is the same before and after. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [March 31, 2011, 7:30pm UTC](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345/54 "2011-03-31T19:30:35Z")
Fighting ignorance is always painful. Especially for we, the ignorant. Sigh. Tris [Previous page](https://boards.straightdope.com/t/do-batteries-get-heavier-when-you-charge-them/576345.md?page=2)