(Mis-)Information for Laptop Users?

In July 2006 an email was sent out to everyone in my company. It was entitled, “IMPORTANT INFORMATION FOR LAPTOP USERS”. Read on, and be informed.

The original email read as follows: 

The following information is for anyone who uses a laptop computer.

Please note that it is very important if you use a laptop, to ensure that you regularly use it from the battery power supply as opposed to plugging it into the mains electricity. This is because the battery needs to be used in order for it to recharge fully and maintain its lifecycle. The average life expectancy of any laptop battery is only 2 to 3 years.

The following is the most effective way of ensuring you get the best performance from your laptop battery.

1. Use your laptop from the battery power supply until you receive a message saying that you should change your power outlet.

(This message indicates that the battery has run down to approximately 10% capacity)

2. Swap to mains power for about 4 hours after which time the battery will have recharged to full capacity.

3. Use the laptop from the battery power supply again and continue with the above cycle of events.

If you have any queries regarding the above, please contact the ICT Helpdesk for advice.

Something about this advice simply didn’t ring true to me. So, I sent this reply:

Out of curiosity, I did a web search for more information about prolonging battery life. I was surprised to discover a number of web sites whose advice conflicts with that given below, and little on the web that supports it.

Specifically, there seems to be a consensus that:

  • Letting Lithium Ion (or “Li-Ion”) batteries discharge completely will do them harm.
  • Li-In batteries should be kept cool.
  • Li-In batteries do not suffer from “memory effect”, unlike some older battery technologies.

The main disadvantage to Li-Ion batteries is that they lose about 10% of their usable capacity each year due to chemical breakdown within the cells. There is nothing that can be done to prevent this condition.

Several sites suggests that you can maximize the useful life of your Li-Ion batteries by keeping them on the charger during use (e.g. laptop computer) or keeping them on the charger when not in use. This is because Li-Ion battery life is dependent on the number of discharge cycles, anything you can do to minimize the number of discharge cycles will, in effect, increase the battery’s useful life.

Also, several sites suggested that, because Li-Ion batteries are “smart” batteries, they cannot be overcharged.

As my laptop has a Li-Ion battery, the above suggests that it would be better to keep it plugged in and charged; or, better still, removed from the laptop altogether as I use it in the office most of the time anyway. I am concerned, however, that this conflicts with the advice given.

To this, I received a reply that stated:

I have forwarded your comments on to our hardware team…

And that was it. I never received a response.

So, you can imagine what is going. Everyone in the company who has a laptop engages in this ritual where they unplug the thing and wait until just before there is no power left. Then they fiddle around under their desks, frantically trying to plug in their laptop before their work vanishes. Four hours later (do they set an Outlook reminder to make sure they don’t miss the occasion?) they unplug and wait for their battery to all-but expire. Then they do it all again. and again.

As far as I understand it, this achieves the following:

  • Stressing the power connector on the back of the laptop, risking hardware failure and the resultant loss of productivity
  • Stressing the battery in the laptop, so reducing the life of their equipment
  • Stressing themselves
  • Wasting company time
  • Wearing out the knees of their trousers as they grub around on the floor plugging and unplugging their power cables.

Nevertheless, it would be remiss of me not to follow the original advice to the letter. After all, it is company policy.


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