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I'm using my laptop at home with battery removed and only connected to the AC power. However I'm lacking the mobility as my power cord is kinda short. Is it safe from electrical point of view to plug in the battery while the laptop is connected to AC and disconnect the AC power afterwards?

What about the opposite side of the question - is it safe (or what the damage could be) if you work on battery, plug in the AC and unplug the battery?

If there are differents for different models of laptops, I'm asking about IBM Lenovo T60. Is there such thing as a 'hot-plug battery'?

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See this question for the drawback of working without the battery, superuser.com/q/344230/147104 –  FredrikD Aug 9 '12 at 8:25
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5 Answers

up vote 5 down vote accepted

Most laptops have hot-plug batteries, which allows you to go to line power for a few moments so that you can swap out your nearly-dead battery for your fully-charged spare. I see Lenovos as being no exception to this.

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Just in addition to this, you can use AC as your main power on the laptop as well, not just for a few moments, although the OP has already figured that out :). –  Azz Sep 27 '10 at 6:08
    
@Azz: That depends on the laptop. Many Thinkpads, for example, cannot do this because they cannot supply the surge of power the CPU needs when it comes out of a halt state without the battery. –  David Schwartz Oct 8 '11 at 6:07
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Personally I wouldn't risk it. If, as you say, the power cord is short there's a good chance it'll come out during the operation anyway.

Laptop batteries are designed to be left in whilst the unit is on mains power anyway so you're not really gaining anything by removing the battery unless you're not going to be using the battery for an extended period.

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Removing the battery may lengthen its life. If you remove it after decharging, then it will last longer than if it is always fully charged. –  petersohn Apr 16 '10 at 14:54
    
@petersohn - I've updated the last sentence to clarify it (hopefully) –  ChrisF Apr 16 '10 at 15:20
    
Li-Ion batteries have a lifespan of about 1-2k cycles. I know it is probably not worth it, but I'm trying to save a few cycles. And I do really need a battery at weekends when I'm travelling. –  Ivan Petrushev Apr 16 '10 at 16:47
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Li-Ion batteries care less about cycles than simply about time and temperature. If you have a T60, then temperature isn't a problem since the battery is away from everything that generates heat on purpose (I see the same with my R60 and my Dell laptop). That being said, I have never seen a laptop battery die because of fiddling with it while the power cord was plugged in. I highly doubt there will be any effect at all; there's pretty much of electronics in the way to ensure various things. –  Joey Apr 16 '10 at 17:01
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I just tried plugging my battery while on AC, and no sullen damage. ~im using Lenovo G460

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No, you can't change batteries while the laptop is plugged in. Follow these steps:

  1. Turn the laptop off or put it in Hibernate mode
  2. Unplug the AC adapter from the wall
  3. Unplug the AC adapter from the computer
  4. Unplug any other wires connected to the laptop
  5. Remove or connect your battery

If you don't follow these steps, you could be injured.

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Insofar as I have successfully tried on different models of a Dell, an Acer and a Gateway, both old (down to 2007), and brand new - I haven't noticed any problem with hot-swapping batteries.

Just a note, even though I'm guilty for doing it I don't know if there's any use to take out a battery after it has been discharged to save cycles since I've read that only applies to older batteries; therefore, you will only want to hot-swap when you're actually hot-swapping 2 batteries and not just taking one out.

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