Replacement laptop batteries cost anything from about £40 to £150. That’s a lot of money, so it makes sense to treat your battery so as to give it the best chance of outlasting the machine. It is very common for the battery to fail after two to three years, but you probably want the machines to last from three to six years.

The best treatment of the battery varies depending upon the type. Somewhere on the battery itself (and you may need to remove it from the machine to find the relevant label), you should find a description as being “Li-ion” (or “lithium ion”) or “NiMH” (or “nickel-metal hydride”.)

NiMH batteries – completely drain the battery every now and again. Do this by using the machine while it is not connected to the power supply until the machine tells you the battery is flat and needs to be re-charged. Do this every month or two. There may be more specific instructions about how often to do this either on the battery itself or on documentation that came with it. If you always use the laptop connected to the mains then the battery will last longer if you completely remove it. If you do this, then put it back in and drain/re-charge it every few months. Incidentally, it can make a laptop much more confortable to use on your lap if the battery isn’t connected as the battery weight is a considerable part of the total weight.

Li-ion batteries – here the advice is NOT to drain the battery completely. On the contrary, keep some charge in it at all times. Again, I would recommend removing it entirely if you are usually connected to mains power, but check it occasionally to make sure it’s got some charge in it and top it up every now and again (see below for checking the charge). The advice with Li-ion batteries is to store them partially charged.

How do you know if the battery is “wearing out”?

It probably won’t charge to 100% and the amount of time you get on each charge reduces. You may eventually get a message popping up telling you to replace the battery.

Remove a nearly dead battery?

It seems sensible to leave a dying battery in the laptop while running the machine off the mains. The theory, of course, is that if the power supply is interrupted then you still have an opportunity to close everything down nicely without problems. Normally I agree, but if you start to get strange things happening to your computer – such as a noticeable time lag between hitting a key and seeing it onscreen – then try removing the failing battery. It seems as if the laptop diverts power to charge a failing battery at the expense of other parts of the system. I may be wrong on why this happens, but it is certainly the case that “keyboard lag” can sometimes be cured by removing a failing battery.

How can I tell how charged the battery is?

Both Macs and PCs have options for displaying an on-screen icon that shows how much charge is in the battery. When the battery is not connected, you can usually get an idea of its state of charge by a series of LED lights on the underside of the battery that are accompanied by a small button (see illustration – yellow highlight). Pressing the button will illuminate the number of LED lights that correspond to the current state of charge.

How do I remove the battery?

Turn the laptop upside down. Batteries come in all sizes and proportions but you are looking for a rectangle that has one or two catches along one side. Typically, one of these catches is not spring-loaded so you can slide it to the open position (usually indicated by an open padlock symbol) and let go. Then push the other catch against the spring and slide or lift the battery out of the case at the same time. See the red highlights in the illustration for spring-loaded and non-sprung catches on a Samsung Q35 battery. Mac batteries are often held in place with a button with a slot across it. Turn the slot by 90 degress and the battery can be removed. Some Mac batteries can’t be removed except by professional repairers as they are entirely contained within the case rather than attached to the underside of it (eg the MacBook Pro).

Extending Battery Life

Given that it would be nice to extend the battery’s life so that it never needs replacing, it may be worth bearing in mind that the more a battery is used, the more of its life is used up, so reducing un-necessary use of the battery may help. Apart from completely removing the battery and running off the mains for most of the time, here are a few suggestions for reducing battery use:

  • Ensure that the laptop at least goes into “sleep” mode if left unattended when running from the battery.
  • All operating systems have options for balancing computer performance against the length of time each battery charge will last. The longer each charge lasts, the longer the battery itself will last.
  • Try to keep the air vents around the casing of the laptop clear of dust, fluff, and nearby obstructions. A good flow of air through the laptop is essential to keep the electronics working within specific temperature limits. If it gets hot then the fan will cut in. The fan needs power and this will come from the battery if the laptop is not connected to the mains. The best way to keep the vents clear of dust is by blowing air into them from an “air duster” (a can of compressed air – available from PC World, Maplins, Rymans etc).

Should I turn off my computer at the end of the day or leave it on?
Off-switch

1) A computer that is switched on is a fire hazard

I have never heard of a computer catching fire, so I did some Googling. There were suprisingly few results (about 30,000) to the phrase “computer caught fire” and almost all of them seemed to refer to “enthusiasts” making their own machines, overclocking, and so forth. I found nothing to suggest that I should worry more about a professionally-built computer than I should worry about, say, leaving my fridge or TV switched on.

2) It takes more electricity to switch off and on than to leave it on. A variation of this is that it wears out the components faster if you switch the machine on and off as compared with leaving it on

These seem to be a type of “cyber myth”. I can find no evidence at all one way or the other.

3) Switching the computer off at night makes it run faster

This is true up to a point (with Windows computers, anyway) but not as much as it used to be. However, it’s not the good night’s sleep that’s done it good, but the re-boot (which has flushed the memory out). Windows computers used to run slower and slower the longer they were left switched on as more and more of the memory was allocated to programs and not then released when the program was closed. I seem to remember that in the days of Windows 3 it would have been unheard of to leave a computer on for days on end. It would just grind to a halt. These days this is hardly an issue – if at all. Windows and the programs using it are much better written and there’s much more memory available.

4) It’s far more convenient to leave it on as it takes so long to boot up from scratch

Undoubtedly. I suspect that computers take as long to boot up now as they did 25 years ago. However, “standby” (sleep mode) is almost as quick to re-start as leaving it fully awake and alert.

5) The computer can’t do background tasks and housekeeping tasks if it is switched off

True, but a computer that is asleep (ie in standby mode) can be woken automatically to perform scheduled tasks and then be put back into standby.

6) The computer is not available as a server if it’s switched off

Can’t argue with that. If, for instance, you use a program like TeamViewer to access a machine remotely then that machine has to be switched on!

7) Turning computers off saves electricity.

This is being perceived as more and more important, but it’s nowhere near as clear-cut as you might expect. I tested the power consumption of two of my laptops and my (oldish) Compaq desktop under different conditions. These results are not scientific and the short test time (about one hour for each condition) means that they should be taken as nothing more than a guide. In the laptop tests, the laptop’s own battery was connected and fully charged. In all cases, only Windows plus security programs (firewall, antivirus) were running. Just out of interest, I also tested the consumption of my TV (a Sony Bravia LCD of reasonably modest screen size). The results were as follows:

Power consumption - chart 1

From these results, one thing is very clear. From the point of view of power consumption, there is no point at all in switching off a computer if you leave it connected to the power supply. The power usage is almost exactly the same as leaving it in standby (sleep) mode.

Is it worth switching it off?

It’s almost impossible to apply an average cost of electricity to this analysis as it depends on the company, the tarriff, the price at the margin of use etc. It seems that a kwh (kilowatt hour) of electricity can be anything from 4p to 20p. As guide, though, the next table shows the total kwh that a machine would consume over a complete year. If you know how much your electricity is costing per unit then applying that figure to the annual consumption will give an idea of the potential savings (but remember that your computer may be in use for, say, 25% of the time so savings during that time would not be so high).

Power consumption - chart 2

My own rule of thumb is that I leave machines in sleep mode (standby) if I’m expecting to use them in the next 24 hours and switch them off otherwise.

Memo to self: unplug it if switching it off. Switching it off and leaving it plugged in is pointless. It’s a much better compromise to leave it in sleep mode.

© 2011-2017 David Leonard
Computer Support in London
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