# Does a battery weigh less as the charge leaves

**URL:** <https://boards.straightdope.com/t/does-a-battery-weigh-less-as-the-charge-leaves/995796>\
**Category:** Factual Questions\
**Created:** [January 8, 2024, 10:39pm UTC](https://boards.straightdope.com/t/does-a-battery-weigh-less-as-the-charge-leaves/995796 "2024-01-08T22:39:18Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\
**Post date:** [January 10, 2024, 5:03pm UTC](https://boards.straightdope.com/t/does-a-battery-weigh-less-as-the-charge-leaves/995796/21 "2024-01-10T17:03:01Z")

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> [@Ruken](#):
>
> Note that an electric plane doesn’t have to run off batteries; it can generate electricity on board (just like BEV vs FCEV cars.) There are supposedly some advantages to electrification that I don’t understand or recall but probably referenced in another thread.

The advantage to a partly electric airplane is similar to the advantages of a hybrid car where a small motor charges a big battery: You can size the engine for cruise, and use the battery as a temporary booster for takeoff, goaround, or failure scenarios.

An engine sized for cruise will be more fuel efficient than one sized for full blast takeoff power.

Whether that incremental efficiency from cruise-sizing will pay for all the rest of the e-system’s size, weight and complexity is the question. In the case of cars the answer is “definitely yes”. In the case of smallish planes the answer today is “yes, but it’s not a slam-dunk total game changer. Yet.”

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**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\
**Post date:** [January 10, 2024, 8:11pm UTC](https://boards.straightdope.com/t/does-a-battery-weigh-less-as-the-charge-leaves/995796/22 "2024-01-10T20:11:12Z")

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> [@Jasmine](#):
>
> Well, I Googled the question, and Google came up with this link:
> 
> [**Does electricity have mass and weight?**](https://www.electricrate.com/data-center/does-electricity-have-weight/)

Wait, that can’t right… because that would mean that someone copy and pasted info from another sight to use on their own. Surely, that doesn’t happen, does it!?

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**Author:** ![Jasmine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jasmine/32/2964_2.png) [@Jasmine](https://boards.straightdope.com/u/Jasmine)\
**Post date:** [January 10, 2024, 8:15pm UTC](https://boards.straightdope.com/t/does-a-battery-weigh-less-as-the-charge-leaves/995796/23 "2024-01-10T20:15:01Z")

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Well, all I can do is post where _I_ got it. The rest is speculation I’m afraid.

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