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View Full Version : Is it harmful to use the laptop on AC when the battery is in?



legolas_w
January 22nd, 2010, 08:51 PM
Hi,

I am being warned by few friends that if I continue using my laptop plugged to AC power without taking the battery out, my battery life will shorten. is there something like that true?

I have a Lenovo T400 which I purchased a year ago.

Thanks.

doas777
January 22nd, 2010, 08:55 PM
not that I have ever heard, but with some older batteries, you do have to let them fully discharge every once in a while, or they will only ever recharge a small portion of the amount used.

Grifulkin
January 22nd, 2010, 08:57 PM
Short answer, yes. Don't overcharge it, I have done that with this laptop, and eventually it got down so far I stopped caring so right now it is at about 17% designed capacity.

Best bet is to charge it to about 40% and take it out if you are going to be on AC.

ratcheer
January 22nd, 2010, 09:04 PM
A lot of people say it is harmful, but I have seen many laptops used this way for several years, with no apparent damage or problems.

Tim

clanky
January 22nd, 2010, 09:05 PM
If you are using the laptop on AC power then remove the battery. If you are using battery power then whenever possible fully charge the battery and then fully (or almost fully) discharge it again.

Modern batteries are more robust than previous types, but the above is still good advice.

juancarlospaco
January 22nd, 2010, 09:07 PM
It can produce spacetime wormholes.

myth1914
January 22nd, 2010, 09:09 PM
A lot of people say it is harmful, but I have seen many laptops used this way for several years, with no apparent damage or problems.

Tim

Agreed. I believe with Lithium Ion batteries, which most if not all laptops use these days, it should not be an issue.

It is true that using the battery will eventually wear it out, but I've had multiple laptops over recent years, used daily. I leave it plugged in and on all day every day and I'm probably down to about 80% of capacity after about 1.5 years.

Mileage will vary, but similar to the circuit in a float charger, it will only maintain the battery charge when left plugged in.

foldingstock
January 22nd, 2010, 09:24 PM
Batteries have a finite capacity where they are able to be charged completely. After this limit is reached, their charge capacity dwindles. If you leave a battery in while on AC, it is in a constant "charge" state and, depending on design, can die faster.

Modern batteries are much better in this regard, but if you plan on being connected to AC power for a long time, it isn't a bad idea to remove the battery.

Also keep in mind that it is harmful for lithium batteries to be completely drained. This will also quickly reduce battery life and total capacity.

init1
January 22nd, 2010, 09:25 PM
I suspect it is. I have done that for quite a while on my laptop, and my battery life is only about 30 minutes or less after a few years.

juancarlospaco
January 22nd, 2010, 09:27 PM
Battery = 2 Years

insane_alien
January 22nd, 2010, 09:30 PM
any modern laptop(last decade) will have a complex enough battery control system in it the when on AC and battery is fully charged, it will not charge the battery anymore.

the situation of having the battery in or out on AC power then becomes identical.

i've never taken the battery out of my laptop and it still has 99% of design capacity despite 2 years of use with lots of on AC time as well. if anything the battery just acts like a UPS.

lovinglinux
January 22nd, 2010, 10:22 PM
Well, I have a lot of power outages here (6 since November), so having the battery removed is not an option.

pricetech
January 22nd, 2010, 10:27 PM
It used to be true, but not any more. Modern batteries are better and modern laptops are better at "knowing" when and how much to charge them.

Having said that, I'll say this; If it makes you feel better to take it out, go ahead. It won't hurt a thing.

gletob
January 22nd, 2010, 10:32 PM
If you are using the laptop on AC power then remove the battery. If you are using battery power then whenever possible fully charge the battery and then fully (or almost fully) discharge it again.

Modern batteries are more robust than previous types, but the above is still good advice.

You're thinking of NiMH or NiCd.

Li-Ion batteries are designed to not have problem's with "Battery memory" meaning that it doesn't matter where you start charging at. Further more, unnecessarily drain of the battery shortens the Li-Ion batteries life.

aysiu
January 22nd, 2010, 10:38 PM
From What you need to know about Lithium-ion Batteries (http://www.geekwithlaptop.com/what-you-need-to-know-about-lithium-ion-batteries):
For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally.

I highly recommend not leaving your laptop or notebook plugged in all the time.

An ideal use for a Road Warrior like myself who uses their laptop a lot while traveling is run on battery power as much as possible, then plug it in at the office, hotel or at a coffee shop, etc. to charge. This helps keeps the battery juices flowing and happy. From What’s the Ideal Strategy to Maximize Notebook Battery Lifespan? (http://theappleblog.com/2008/10/29/whats-the-ideal-strategy-to-maximize-notebook-battery-lifespan/):
Isador Buchmann advises not leaving the battery in the computer with the AC adapter plugged in unless you’re actually charging it, and storing it in a cool place at about a 40 percent charge, maintaining that the most harmful combination is full charge at high temperature.

However, one of the reasons I’m a laptop fan and user is to avoid data loss when there’s a power outage and to be able to keep on computing during blackouts. For those purposes the battery needs to be in the computer and fully charged. From Learn how to maximize battery performance (http://www.usatoday.com/tech/columnist/kimkomando/2005-08-07-battery-life_x.htm):
With lithium-ion batteries, partial charges and discharges are best on a regular basis. These batteries do not develop memory problems.
It's best to use your batteries regularly. But sometimes you have to store them, and storage can pose problems.

Don't store batteries completely discharged. A 50% charge is optimum for storage. The first thing you have to realize is that lithium ion is designed to die slowly over time, regardless of how you use it or don't use it. The minute it leaves the factory, it's already dying.

Optimally, you want to be making small discharges and charges on a regular basis. You won't damage the battery by leaving it plugged in and charged all the time, but everything I've read about lithium ion indicates it's best to regularly charge and discharge (but not fully discharge).

So if all you care about is maximizing your battery life, the best thing to do is discharge to about 50% and then store the battery in a cool, dry place while you leave your laptop plugged in.

One of the sites I linked to brings up a good point, though, which is the battery being a backup in case of a power failure. For that reason (and it being a pain to have to keep removing and putting back in the battery), I leave my battery in all the time. I generally leave my netbook plugged in all the time if I'm not traveling (which is most of the time), and every now and then I'll just unplug it and re-plug it back in just to have a little discharge and recharge.

Ultimately, I don't think there's much room to go wrong. As I said before, lithium ion is not designed to last forever. No matter what you do, battery life will go after a few years.