I've heard people saying that your battery should be (almost) completely discharged before you recharge him.
Also some people say that you shouldn't leave the battery in when its completely charged (and you're working on AC mode).
Also if you don't use your battery for a long time, would that also harm your battery's capacity?
I believe you should not charge your battery until it is mostly discharged. It also is bad for it to leave it in your PC when on AC but I wouldn't drive your self crazy worrying about the battery because you can go out and replace it at any discount electronics store for a reasonable price and they only last a year or so anyway. I personally don't leave my battery in my Laptop but I make sure to charge and discharge once a month.
Batteries in portable consumer devices such as a laptop, camcorder, cellular phone, etc., are typically made using either Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH) or Lithium Ion (Li-Ion) battery cell chemistry. Each type of rechargeable battery chemistry has its own unique characteristics
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