Should you leave your laptop plugged in and charging when you’re not on-the-go? What’s best for the battery? What’s best for your user experience? Read on as we investigate.
The Questions
When your laptop’s battery is 100% charged, should you leave it plugged in so any battery power doesn’t get used, or will that cause overcharging, overheating, etc.? Should the laptop be unplugged when the battery level is 100%?
When I’m at home, is it better to use the laptop plugged into AC power, or with just the battery, for the overall battery life?
So what was the verdict? Should you leave your laptop almost perpetually tethered to the wall or only charge it when the battery charge is running low?
The Answers
The answers to the questions isn’t a cut and dry “Yes, leave it tethered” or “No, unplug it” because of the variety of laptop designs, their battery types, and the integrated charging circuit that recharges the battery.
It won’t make all that much difference. What will shorten battery life is temperature: If it gets hot, it will shorten the battery life. Best thing to do, if you are able, is to remove the battery while you’re at home and keep it somewhere cool.
If it’s a Li-ion battery, then they don’t like to be completely discharged, so make sure you charge them regularly.
Wikipedia on Li-ion batteries
Lithium-ion batteries should not be frequently discharged fully and recharged (“deep-cycled”), but this may be necessary after about every 30th recharge to recalibrate any electronic charge monitor (e.g. a battery meter). This allows the monitoring electronics to more accurately estimate battery charge. This has nothing to do with the memory effect.
Question
What about the “Remove the battery!” camp? It turns out that while removing the battery can be beneficial, the situations in which it is beneficial are fairly limited.
Answer
Having a battery fully charged and the laptop plugged in is not harmful, because as soon as the charge level reaches 100% the battery stops receiving charging energy and this energy is bypassed directly to the power supply system of the laptop.
However there’s a disadvantage in keeping the battery in its socket when the laptop is plugged in, but only if it’s currently suffering from excessive heating caused by the laptop hardware.
So:
In a normal usage, if the laptop doesn't get to hot (CPU and Hard Disk around 40ºC) the battery should remain in the laptop socket;
In an intensive usage which leads to a large amount of heat produced (i.e. Games) the battery should be removed from the socket in order to prevent unwanted heating.
The heat, among the fact that it has 100% of charge, is the great enemy of the lithium battery and not the plug, as many might think so.
The best plan of attack then, is to monitor your hardware to ensure you’re not overheating your battery and be concious of the limitations of the type of battery in your device–for the majority of users, a Lithium-Ion battery.
