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30327
February 21st, 2012 12:00
Best Laptop Charging Practices... ?
If I remember correctly, NiCad and NiMH batteries lifetimes were measured in terms of the number of recharge cycles that those battery types could sustain. I do not know about the Lithium Ion batteries laptops are using now, though. So, two questions:
First, when you plug in a laptop into a power supply, does the laptop draw power from the external power supply, or from the internal battery with the external power supply simply serving as a trickle charger for the laptop battery?
Second, presuming that the external power supply is serving as a trickle charger, would you get longer life from your laptop battery if you leave your laptop plugged in as much as possible, or if you drain the battery down consistently then recharge?
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jackshack
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February 21st, 2012 13:00
How much detail do you wish? A good general education on many types of batteries can be found here: http://batteryuniversity.com/. I believe what you are asking will be found in the section titled "The Battery and You."
Following all the suggestions found in that paper can be a bit of work, and being lazy, I personally take some short-cuts. Beginning with your first question:
When attached to the AC power adapter, the battery is charged while the AC adapter also powers the laptop. Batteries in general do not fare well when kept continuously on charge with never a discharge, so most chargers either shut down completely or slow to a very small trickle when the battery reaches full charge.
Second: I have used NiCd, NiMH, and presently, Lithium battery technology in my various devices. None of these battery types do well if left forever on charge and never go through a discharge cycle. Also, while all are rated for a given number of charge/discharge cycles, they seem able to do better if they are never fully discharged. Indeed, complete discharge of a lithium ion battery can kill it, so the battery circuits are designed to halt discharge of the battery somewhere around 10%. Most of our experienced forum members have recommended removing the battery if the laptop will be left forever on charge and almost never used on battery. Before I retired, I used a Dell Latitude C640 at a docking station at my desk. It seldom traveled with me, so I plugged the setup into a power strip so that I could switch off the AC when I left work in the evening. The office was climate controlled so I didn't have to worry about heat or extreme cold. I used the laptop in that fashion for about five years, and when I needed to run on battery, the computer would still run for nearly two hours on the original battery.
I treat my personal laptop much the same way. I purchased an Inspiron 5160 in October, 2004. I normally use it with the AC adapter, but when not in use, I unplug the adapter and store the computer in a cool place. Those old Lithium ion batteries will still run the laptop for over an hour despite being eight years old. Now I caution you that while this procedure has worked well for me, it is not necessarily the best approach, and as I have heard, your mileage may vary.