# how much cheaper would laptop battery be if we only wanted 30 mins of power, not 4 hours? **URL:** \ **Category:** Factual Questions\ **Created:** [March 13, 2011, 8:05pm UTC](https://boards.straightdope.com/t/how-much-cheaper-would-laptop-battery-be-if-we-only-wanted-30-mins-of-power-not-4-hours/574576 "2011-03-13T20:05:26Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 14, 2011, 6:09pm UTC](https://boards.straightdope.com/t/how-much-cheaper-would-laptop-battery-be-if-we-only-wanted-30-mins-of-power-not-4-hours/574576/21 "2011-03-14T18:09:31Z")
Just leave your laptop plugged in. What everyone is missing is this: Lithium batteries have a finite life whether you use them or not. Sure, you can extend their life by storing them at a low state of charge, but that is a pretty inconvenient thing to do, and still leads to 15% capacity loss in 4 years. Best case, you are only going to get 300-500 cycles or 3-5 years out of a battery, no matter how much you baby it. I currently have 341 cycles on my MacBook battery, and I still get 2.5 hours of life out of it on a full charge. I leave it plugged in all day at work, and then take it home asleep. It also sleeps all weekend. ETA: more info here: [BU-808: How to Prolong Lithium-based Batteries - Battery University](http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries) ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [March 14, 2011, 9:22pm UTC](https://boards.straightdope.com/t/how-much-cheaper-would-laptop-battery-be-if-we-only-wanted-30-mins-of-power-not-4-hours/574576/22 "2011-03-14T21:22:13Z")
I take your point, but I am not sure that the page you link to really supports your position: > [@](#): > > Because batteries are used under many demanding environmental conditions, manufacturers take a conservative approach and specify a battery life between 300 and 500 discharge/charge cycles. Life cycle testing is easy to measure and is well understood by the user. Some organizations also add a date stamp of three to five years; however, this method is less reliable because it does not include the type of use. > > ``` > . . . > > ``` > > The worst condition is keeping a fully charged battery at elevated temperatures, which is the case when running a laptop on the power grid. Under these circumstances the battery will typically last for about two years, whether cycled or not. The pack does not die suddenly but will produce decreasing runtimes as part of aging. It looks to me, from what they say there, that by storing my battery, most of the time, while I am running the computer off the mains, at about 40% charge level, I could pretty much double its useful life, from about two years to about the 4 that you suggest is a reasonable expectation. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 14, 2011, 9:33pm UTC](https://boards.straightdope.com/t/how-much-cheaper-would-laptop-battery-be-if-we-only-wanted-30-mins-of-power-not-4-hours/574576/23 "2011-03-14T21:33:57Z")
> [@njtt](#): > > I take your point, but I am not sure that the page you link to really supports your position: > > It looks to me, from what they say there, that by storing my battery, most of the time, while I am running the computer off the mains, at about 40% charge level, I could pretty much double its useful life, from about two years to about the 4 that you suggest is a reasonable expectation. Yeah, great - all you need is a telepathic charge controller! See, most people want to **USE** their laptops. They don’t want to unplug the laptop from the wall (where it’s been “charging” all day), and find that they only have 2 hours of battery life when they should have 5 - because the charging circuitry was trying to maximize battery longevity! That’s why all these schemes to increase battery life are just a red herring - keep your battery full, and just put up with a 3-year lifespan. Spending $100 every three years on a new battery is only a dime a day - isn’t it worth that to actually be able to use your machine on the road without worrying whether it is fully charged or not? ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [March 14, 2011, 10:13pm UTC](https://boards.straightdope.com/t/how-much-cheaper-would-laptop-battery-be-if-we-only-wanted-30-mins-of-power-not-4-hours/574576/24 "2011-03-14T22:13:23Z")
> [@beowulff](#): > > Just leave your laptop plugged in. > > What everyone is missing is this: Lithium batteries have a finite life whether you use them or not. Sure, you can extend their life by storing them at a low state of charge, but that is a pretty inconvenient thing to do, and still leads to 15% capacity loss in 4 years. Best case, you are only going to get 300-500 cycles or 3-5 years out of a battery, no matter how much you baby it. I currently have 341 cycles on my MacBook battery, and I still get 2.5 hours of life out of it on a full charge. I leave it plugged in all day at work, and then take it home asleep. It also sleeps all weekend. > > ETA: more info here: [http://batteryuniversity.com/learn/article/how\_to\_prolong\_lithium\_based\_batteries](http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries) Re my experience with the last 3 Li-on battery tech notebooks I’ve owned. I’ve used them plugged in 99.99% of the time. Battery life uptime after 2 years (when I sold them) was approx 55% - 65% of new. About what I would expect if not plugged in. Keeping them plugged in does not appear to negatively impact battery life vs cycling them. ---
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [March 14, 2011, 10:24pm UTC](https://boards.straightdope.com/t/how-much-cheaper-would-laptop-battery-be-if-we-only-wanted-30-mins-of-power-not-4-hours/574576/25 "2011-03-14T22:24:43Z")
> [@beowulff](#): > > Yeah, great - all you need is a telepathic charge controller! > See, most people want to **USE** their laptops. They don’t want to unplug the laptop from the wall (where it’s been “charging” all day), and find that they only have 2 hours of battery life when they should have 5 - because the charging circuitry was trying to maximize battery longevity! That’s why all these schemes to increase battery life are just a red herring - keep your battery full, and just put up with a 3-year lifespan. Spending $100 every three years on a new battery is only a dime a day - isn’t it worth that to actually be able to use your machine on the road without worrying whether it is fully charged or not? I agree. And it isn’t $100 every three years–for me it’s more like $38. I once bought an extra battery with a new laptop–used and charged it about three times. The thing still died after three years. Moreover, I want to have the battery there when I’m on mains, in case of power outages. (Which happen often, where I go.) [Previous page](https://boards.straightdope.com/t/how-much-cheaper-would-laptop-battery-be-if-we-only-wanted-30-mins-of-power-not-4-hours/574576.md?page=1)