I have two laptops (same manufacture), with the same type of power connector.
However, the power supplies/transformers are slightly different.
The output on the first laptop's power supply is 15.6 V at 8.0 A. The output on the second laptop's power supply is 15.6 V at 5 A.
Clearly the voltages are the same, but the currents are different. I assume the second laptop's power supply can not be used on the first, because it can't supply enough power to the laptop.
However, can the first laptop's power supply be safely used on the second laptop?
Users often ask if they should leave their laptop plugged in all the time as there are a number of myths surrounding this. During this informative blog, we will separate the fact from the fiction in order to answer the question ‘should a laptop be plugged in all the time?’.
The first thing to know is that there is no correct answer to this question. Some “experts” will tell you that leaving your laptop plugged in all the time with the battery in, will cause damage to it. But, on the other hand, they will tell you that charging your laptop battery every day is also not a bad idea.
If you leave your laptop plugged in all the time, there’s no danger of overcharging the battery. This is because as soon as it hits 100 percent, it will stop charging until the voltage falls below a certain level. You do, however, need to ensure that your laptop does not overheat!
What is indisputable is that your battery will lose capacity if you leave your laptop plugged into a mains outlet all of the time. It won’t happen immediately, but if you do this this for around a year or so, you will significantly lessen the capacity of your laptop battery.
We’ll explain how to avoid this later.
In the “old days” the early laptops were powered by nickel-cadmium (NiCad) or nickel-metal hydride (NiMH) batteries. Therefore it was possible to overcharge the battery so, understandably, the advice was to always turn off and unplug your machine as it was possible to cause irreparable damage.
In addition, over a number of charge cycles, these batteries developed a “memory effect”. This meant that the battery would think it was charged to full (100%) capacity when actually it was perhaps only 70% charged.
As a consequence it would stop charging – thus lasting a shorter and shorter time.
However, modern laptops are almost always powered by a lithium-ion (Li-ion) battery and lithium ion batteries have this problem to a far lesser degree. It is also much more difficult to damage lithium batteries.
That rather depends on what you mean by “better”. Leaving a laptop plugged in means it is (almost) instantly available for use with no annoying wait while it starts up. Also, should you need to take your laptop out and about you know that it will have a fully charged battery.
Although modern battery technology enables most laptops nowadays to last a lot longer without plugging in a power cable, your laptop’s battery life is finite. So, if you have a long day’s work planned, it is probably best to draw power from the mains.
Another consideration is that many laptops are set up to optimise the life of their batteries by using less energy when running on battery power alone, so if you plug your computer into the mains you may find the screen becomes brighter etc.
If you need the very best screen definition, then at Lee Harvey Computer Repairs, we recommend that you are better off working with your computer plugged in.
How many times should you charge your laptop is another of those “how long is a piece of string?” questions.
Many modern laptops – actually most modern laptops – are programmed to prolong the life of their batteries by charging their battery until it is almost (but not quite) fully charged. They also ensure that they do not overcharge.
So the answer is…it depends! To see why “it depends” we need to understand what affects battery life and how you can best look after your laptop’s battery.
The length of life of laptop batteries depends on something called “depth of discharge”.
For example, if you allow your battery to run dry before recharging it back to 100 percent that is one “total charging cycle” so you should avoid discharging your battery completely.
A normal laptop battery is capable of around 300 to 500 “discharge cycles” (empty to full capacity), before it will be time for a replacement.
The larger the average depth of discharge on your battery, the fewer charging cycles you’ll get and the sooner you will need a new battery. The “empty to full” example above is a 100% charging cycle, whereas charging from 80% to 100% is only a 20% charging cycle.
Therefore it follows that if your “average depth of discharge” is just 20%, your battery will last a lot longer before replacement.
There are many other factors that affect how batteries wear – high temperatures etc – but it is inescapable that the more “charge cycles” a laptop’s battery undergoes, the shorter time before you need to buy a new battery.
There is always going to be a finite number of times a battery can be charged, but by never letting it fully discharge and never quite charging it to full capacity, you can increase that number.
Below is the techie way to extending the life of your laptop battery :
Yes, this sounds like a lot of battery pampering and extra work, however, the reward is a battery that’ll still be working long after your laptop is out of date and needs changing.
It is possible to alter your laptop’s settings to do a lot of this automatically and Lee Harvey Computing can do this for you.
In a word – loss of data if the power goes off (OK – 8 words!). Most programs allow you to “autosave” – meaning that the computer saves your work every 5 or 10 minutes. So, if the power suddenly fails, you have only lost, at most, a few minutes worth of your work.
If you need help with this you can ask Lee Harvey Computing to advise you.
The good news is that a laptop takes a lot less power than a desktop computer and even if you go the “unplugged” route you will have to plug in at some point to charge the battery.
A laptop is designed to operate as a portable computer which allows you to work anywhere – on the train, for example. It is plugged in when you reach your office to recharge the battery.
Used this way minimises the effect on the environment but the amount of power used when the laptop is in standby mode is tiny, so the effect on the environment of each choice is more or less equal.
At the beginning of this article we asked, “should I leave my laptop plugged in all the time or should I unplug it when not in use?” As we have seen, there is no clear-cut answer.
It simply depends on:
Will leaving my laptop plugged in damage the battery, use huge amounts of electricity or be dangerous? No, no and no again.
In summary – if you want to leave it plugged in you should do so, but if you want to turn it off after use that is fine too. It really is up to you.