# Does turning a (bike) light to blink/flash conserve battery life?

**URL:** <https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054>\
**Category:** Factual Questions\
**Created:** [November 23, 2008, 12:43am UTC](https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054 "2008-11-23T00:43:24Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![oscar\_1](https://avatars.discourse-cdn.com/v4/letter/o/c77e96/32.png) [@oscar\_1](https://boards.straightdope.com/u/oscar_1)\
**Post date:** [November 23, 2008, 12:43am UTC](https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054/1 "2008-11-23T00:43:24Z")

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My friends seem to think that it doesn’t, and that starting the light up and then off would consume more, but the company which made the light claim it does save energy.

Any help?

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**Author:** ![Tenebras](https://avatars.discourse-cdn.com/v4/letter/t/977dab/32.png) [@Tenebras](https://boards.straightdope.com/u/Tenebras)\
**Post date:** [November 23, 2008, 12:52am UTC](https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054/2 "2008-11-23T00:52:43Z")

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Is there a reason he won’t believe his own lying eyes? Why not take two of them and put them in the garage for a few hours? In my experience the lights last a lot longer on flashy mode than constant mode, but I think the best way of convincing them is to just go ahead and try it out.

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**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\
**Post date:** [November 23, 2008, 1:18am UTC](https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054/3 "2008-11-23T01:18:54Z")

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I think he is confusing the wear and tear of turning on and off incandescent lights. If you have an LED bike light, like I do, his argument really doesn’t hold water. But he may need to see it to believe it…

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**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\
**Post date:** [November 23, 2008, 3:13am UTC](https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054/4 "2008-11-23T03:13:35Z")

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Does turning a (bike) light to blink/flash conserve battery life?

Yes.

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**Author:** ![Dragwyr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dragwyr/32/2855_2.png) [@Dragwyr](https://boards.straightdope.com/u/Dragwyr)\
**Post date:** [November 23, 2008, 3:54pm UTC](https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054/5 "2008-11-23T15:54:13Z")

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FYI, having your bike light set on flashy mode also makes you more visible to others on the road.

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**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\
**Post date:** [November 23, 2008, 5:30pm UTC](https://boards.straightdope.com/t/does-turning-a-bike-light-to-blink-flash-conserve-battery-life/474054/6 "2008-11-23T17:30:47Z")

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> [@Dragwyr](#):
>
> FYI, having your bike light set on flashy mode also makes you more visible to others on the road.

Yes and no. It makes you easier (very slightly easier) to notice, but it’s been reported that flashing lights are much harder to judge in terms of speed and distance.

Cars don’t show flashing lights to the rear (in fact, it’s illegal to do so.) Unless you’re a cop that is. This law in my understanding is not just to not mimic an emergency vehicle; it’s a safety issue as well.