# Extending Battery Life: Constant Re-Charge, Or Let It Go Down To Zero?
**URL:** https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921
**Category:** In My Humble Opinion
**Created:** [May 23, 2011, 5:44pm UTC](https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921 "2011-05-23T17:44:21Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@DMark](https://boards.straightdope.com/u/DMark)
#### Post date: [May 23, 2011, 5:44pm UTC](https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921/1 "2011-05-23T17:44:21Z")
I have a smart phone that I like, but the battery sucks - pretty much goes from a full battery to about 30% in a single day. (New phone, only about 3 months old.)
I also just bought a new laptop (three weeks ago) with battery life about 4-5 hours currently.
So, I have heard different stories:
1. The guy who sold me the laptop said to charge it, then run it off the battery until it dies and then re-charge it. He claims this keeps the battery fresh.
2. The woman who sold me the smart phone suggested running the battery to zero at least once a week and then giving a full charge.
3. Many people I know says this doesn’t save battery life and there is no problem always having it on charge if possible.
Has there ever been a definitive study on the best way to treat new batteries?
Drain and re-charge, or keep fully charged?
---
### Author:  [@Covered\_In\_Bees](https://boards.straightdope.com/u/Covered_In_Bees)
#### Post date: [May 23, 2011, 5:50pm UTC](https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921/2 "2011-05-23T17:50:00Z")
> **[5 Ways to Make Your Cell Phone Battery Last Longer - wikiHow](https://www.wikihow.com/Make-Your-Cell-Phone-Battery-Last-Longer)**
>
> This wikiHow teaches you different ways to extend the battery life of your iPhone, Android, or feature phone (non-smartphone). Turn the phone off. Only do this if it's going to be for several hours, as the process of turning the phone off...
[http://www.techrepublic.com/blog/helpdesk/the-care-and-feeding-of-li-ion-batteries/124](http://www.techrepublic.com/blog/helpdesk/the-care-and-feeding-of-li-ion-batteries/124)
Good reading.
---
### Author:  [@Bosstone](https://boards.straightdope.com/u/Bosstone)
#### Post date: [May 23, 2011, 5:55pm UTC](https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921/3 "2011-05-23T17:55:48Z")
> [@DMark](#):
>
> I have a smart phone that I like, but the battery sucks - pretty much goes from a full battery to about 30% in a single day. (New phone, only about 3 months old.)
FWIW, this is standard for a smartphone. If you’re stingy with the use and turn off unnecessary services, you can prolong the life to 2 days, but short of getting an aftermarket battery they all pretty much require a nightly recharge.
---
### Author:  [@cochrane](https://boards.straightdope.com/u/cochrane)
#### Post date: [May 23, 2011, 6:17pm UTC](https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921/4 "2011-05-23T18:17:09Z")
I leave my laptop plugged in and constantly charging. I believe Windows XP monitors my battery. It will periodically turn off the AC charging and run off the battery for a short time so that it does have a chance to discharge and then switch back to AC power. Also, NiMH rechargeables can be discharged partially and then brought up to a full charge without causing a memory effect, so allowing them to fully discharge isn’t really necessary.
---
### Author:  [@silk1976](https://boards.straightdope.com/u/silk1976)
#### Post date: [May 24, 2011, 5:11pm UTC](https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921/5 "2011-05-24T17:11:21Z")
All depends on the type of battery. The predominant types of rechargable batteries are Nickel Cadmium (Nicad’s), Lithium Ion, and Nickel metal Hydride (NiMH). They all vary in their ability to dump charge over time, their charge memory, and shelf life between charges.
Usually things like phones and laptops have lithium ion because you don’t need the sudden high power output that NiCd’s can deliver, they (Li-ION)have less of a charge memory, and you dont need the long shelf life between charges like NiMH offer. The downside is that, like a previously linked article mentions, their life is measured in charge cycles - so it is not uncommon for laptops and smartphones to start noticing a significant decrease in battery life after a year or two, depending on usage.
---
### Author:  [@kanicbird](https://boards.straightdope.com/u/kanicbird)
#### Post date: [May 24, 2011, 5:57pm UTC](https://boards.straightdope.com/t/extending-battery-life-constant-re-charge-or-let-it-go-down-to-zero/582921/6 "2011-05-24T17:57:12Z")
> [@silk1976](#):
>
> The downside is that, like a previously linked article mentions, their life is measured in charge cycles - so it is not uncommon for laptops and smartphones to start noticing a significant decrease in battery life after a year or two, depending on usage.
With Li-ion the life may be measured by charge cycles, but that’s not necessarily the best measure, but more of a throwback to NiCd/Nimh days.
Li-ion batteries start to degrade as soon as they are manufactured regardless of cycles. Also time at a particular level of charge has a big factor on battery life. At 0% charge a Li-ion battery eats itself pretty quickly and you really don’t want to leave it there long, though I’ve heard that they typically contain circuitry to prevent true 0% charge.
As such with Li-ion time is the major enemy with the time spend at a particular discharge level as a major factor, more then cycle life. If you could keep the device at about 40% charge level you would slow down the degradation by the highest amount.