I am planning to buy a laptop and, as I have never had a laptop of my own before, I have started to read up on the best way to charge a laptop so as not to damage battery life.
Is it all right to charge it to 100%, unplug the charger, let the battery drain to something like 30% and then repeat? Furthermore, does using the laptop while the charger is plugged in harm the battery? I believe that it doesn't, but I just want to make sure that this is the case.
EDIT: I am referring to Lithium-ion batteries.

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    It’s impossible to answer this question. It depends on the battery technology and the charging system. Neither of which we have any information about. You should be able to assume that the manufacturer knows better than you and you should just leave it plugged in and charging unless you need to run it on battery. What is true is that you can only charge and discharge a battery so many times, so that act alone shortens the battery life. – Appleoddity Apr 28 '19 at 15:40
  • According to BatteryUniversity, Lithium-ion batteries prefer not to be charged in deep cycles. But if the battery is easily replaceable, and you need the entire capacity, feel free to use it. – neverMind9 Apr 28 '19 at 15:50
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    I added the fact that I was referring to Lithium-ion batteries. @neverMind9 thank you. – JustAnAmateur Apr 28 '19 at 15:55
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    Possible duplicate of Should laptops remain plugged in when their battery is 100% charged? – slhck Apr 28 '19 at 19:36
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You need to know that:

  • Rechargeable Lithium-Ion batteries have a limited life and will gradually lose their capacity to hold a charge, and this is irreversible.
  • Lithium-Ion batteries continue to slowly discharge (self-discharge) even when not in use or while in storage.
  • Avoid completely discharging batteries.
  • Lithium-ion batteries don't like being charged all the way up and run all the way down. Better to do little recharging here and there.
  • Experts advise that after 30 charges, you should allow lithium-ion batteries to almost completely discharge once, but never totally. (But I don't think that most people bother with it.)
  • You can leave your laptop plugged in all the time, and you cannot overcharge it. Most laptops are smart enough to cut the battery out of charging once it's full.
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    So even when the battery is at 100% I can still leave it plugged in and cause no harm?Would this be better than unplugging it and recharching it later? – JustAnAmateur Apr 28 '19 at 16:43
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    According to the usual advice, you may leave it connected. However, for long periods it might be safer to disconnect to avoid power surges. For very long periods, the battery might self-discharge, and it's said that if it becomes too low it might suffer or even die. – harrymc Apr 28 '19 at 16:47
  • @harrymc The charging circuit does handle selfdischarge and I never had a power surge in my entire life. – neverMind9 May 9 '19 at 18:26

@Harrymc answer is largely correct, but there are additional things you may wish to consider -

  • Lithium batteries age even when not in use - how much depends on temperature and how full it is.
  • Some laptops will allow you to set a maximum charge percentage (in BIOS). A maximum charge of less then say 75% will greatly prolong the life of your battery. You should use this if your laptop is normally left plugged in.
  • Using the charger while battery is plugged in wont typically damage the battery and can prolong the systems life by preventing it from discharging and needing to be recharged. Be aware of CHARGING the battery while using the laptop. This will work fine but can generate more heat - and heat is not ideal for a lithium battery.
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