Shoutbox

What's the effect of leaving a rechargeable laptop battery plugged in while running the laptop using AC power supply?

I searched a bit, asked a few people and some believed that leaving the battery plugged in all the time and not removing it will end up decreasing the battery life, and end up in the battery's exhaustion.

Others believe that it doesn't really matter and does not in any way affect the battery since when the battery's fully recharged AC power will take over and won't affect the battery. So, any views?

Thanks.

It will decrease the battery life to treat it in this way.  The best practice is to remove the battery when it's plugged into the mains.

Then to get the longest battery life when you're using it on battery you should also let it run out completely before charging it back up again.  This is true of ANY device with a rechargeable battery, not just laptops.

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Originally posted by Moh
Others believe that it doesn't really matter and does not in any way affect the battery since when the battery's fully recharged AC power will take over and won't affect the battery.

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I would assume that is true on most laptops. The laptop is smart enough to know when the battery is full. Even a cheap regular battery loader is smart enough to cut power to the battery when the battery is full (or do a trickle load).

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Originally posted by djdannyp
to get the longest battery life when you're using it on battery you should also let it run out completely before charging it back up again.  This is true of ANY device with a rechargeable battery, not just laptops.

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I think you're referring to the memory effect, this is true for NiCd batteries, but AFAIK it doesn't apply to NiMH batteries which almost every laptop now uses. People always seem to contradict each other on these things though, so I would like a definitive answer too .


Personally always ignore the "only charge when it is empty" and "don't leave it connected when it's full" advise. It certainly was true for NiCd batteries and dumb chargers, but it seems just old fashioned advise today. It's not like I will let my phone/battery run out on purpose to find myself with 0% power somewhere where there isn't an power outlet in reach. And it's not like I will wake up in the middle of the night to disconnect my phone from my charger because it is ready. Even if it were better for my batteries. I charge my phone every night whether it's needed or not. When you sync a phone over USB it will also start charging whether you want to or not. Laptops are plugged into a power outlet whenever one is in close reach.

I know from experience that it might not be so good to leave it charging with the battery in all the time. My dad and myself both got same series Acer laptops at around the same time. I've been trying to be as gentle on the battery as possible, using battery power instead of having it plugged in or removing the battery when I can use AC power. As a result, my battery still lasts 1-2 hours, which is similar to when it was new. My dad always has it plugged in, almost 24/7, and his laptop cannot stay powered with the battery for more than 5-10 minutes (not that it matters to him, as he uses it more as a portable desktop than a laptop). Both laptops are from the end of 2007, so I wouldn't call them that old. They were, however, pretty cheap.

When a battery is kept out of use for a long time it should be kept a 50% charge, and extremely cool. (fridge temp)

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Originally posted by Menthix
I would assume that is true on most laptops. The laptop is smart enough to know when the battery is full.

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This is correct.

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Originally posted by Menthix
I think you're referring to the memory effect, this is true for NiCd batteries, but AFAIK it doesn't apply to NiMH batteries which almost every laptop now uses.

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This is correct as well, for the most part. 

NiMH batteries don't have the memory effect, but they are good for a number of charge cycles.  Each charge cycle results in some loss of capacity.  The loss is the same for a partial charge cycle as it would be for a full one.  Sticking to full cycles would usually result in fewer charge cycles during the same time period, so that is still a valid general recommendation.

Along the same lines, taking the battery out when using the laptop on AC power also remains a valid general recommendation, because all rechargeable batteries "bleed" some charge over the time.  You will get occasional short charge cycles even having the laptop always plugged in when you use it, which over time will reduce the battery's capacity.

In practice, however, none of this is worth the trouble.  I am certainly not going to bother taking the battery out, let alone keep it in a fridge.  That defeats the point of having a laptop, which is being able to conveniently pick it up and take it with you as needed.  The battery is a consumable and yes, at some point you will have to replace it just like at some point you have to replace tires on a car.

Just use it as you see fit and it will still last a couple years.

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Originally posted by Lifehacker
Today's laptops use Lithium batteries instead of nickel, but there's a lot of incorrect information out there about how to charge or drain your batteries, so let's set the record straight: Nickel batteries required being fully drained before a recharge to optimize your battery life, but Lithium batteries are the opposite—you do not need to fully discharge it before recharging, and in fact, if you fully deplete a lithium battery and don't recharge for a while, it can become incapable of holding a charge.

You'll also want to make sure that your battery is not always fully charged—Wikipedia points out that if your lithium battery is fully charged all the time, you will lose up to 20% of your capacity every year, no matter what you do. Make sure to discharge the battery sometimes, and if you spend most of your time plugged in at a desk, you would be better off running the battery down to half, and then simply removing the battery and storing it in a cool place. You can use Hibernate mode to save exactly what you were doing while still shutting down the laptop completely.

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http://lifehacker.com/5566020/how-to-maximize-the...our-windows-laptop

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Originally posted by Adeptus
NiMH batteries don't have the memory effect, but they are good for a number of charge cycles.  Each charge cycle results in some loss of capacity.  The loss is the same for a partial charge cycle as it would be for a full one.  Sticking to full cycles would usually result in fewer charge cycles during the same time period, so that is still a valid general recommendation.

Along the same lines, taking the battery out when using the laptop on AC power also remains a valid general recommendation, because all rechargeable batteries "bleed" some charge over the time.  You will get occasional short charge cycles even having the laptop always plugged in when you use it, which over time will reduce the battery's capacity.

In practice, however, none of this is worth the trouble.  I am certainly not going to bother taking the battery out, let alone keep it in a fridge.  That defeats the point of having a laptop, which is being able to conveniently pick it up and take it with you as needed.  The battery is a consumable and yes, at some point you will have to replace it just like at some point you have to replace tires on a ca

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Thanks, very useful! People keep on asking me this, and as everyone else, I always saw way too many opinions, which seemed to go against my experience. this makes sens!

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Originally posted by nimicitor

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Originally posted by Lifehacker
Today's laptops use Lithium batteries instead of nickel, but there's a lot of incorrect information out there about how to charge or drain your batteries, so let's set the record straight: Nickel batteries required being fully drained before a recharge to optimize your battery life, but Lithium batteries are the opposite—you do not need to fully discharge it before recharging, and in fact, if you fully deplete a lithium battery and don't recharge for a while, it can become incapable of holding a charge.

You'll also want to make sure that your battery is not always fully charged—Wikipedia points out that if your lithium battery is fully charged all the time, you will lose up to 20% of your capacity every year, no matter what you do. Make sure to discharge the battery sometimes, and if you spend most of your time plugged in at a desk, you would be better off running the battery down to half, and then simply removing the battery and storing it in a cool place. You can use Hibernate mode to save exactly what you were doing while still shutting down the laptop completely.

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http://lifehacker.com/5566020/how-to-maximize-the...our-windows-laptop

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I'll give this a read as well.