Improve notebook battery life

Posted on 25 Jan 2006 at 17:01

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One thing that does reduce their life, however, is being continually kept in a 100 per cent charged state. Unfortunately, this is exactly what happens if you mainly use your notebook as a desktop replacement and leave it plugged into the mains all the time. Li-ion batteries can't handle this. When you want to take the notebook on the road after several months of being plugged in all the time, you'll find the capacity has been severely reduced.

It's easy to cope with this, though; just pull the mains adaptor's plug out of the back of the notebook at least once a month - you can do this when the notebook is switched on with no ill effects. The battery will immediately kick in. Carry on using the notebook as usual, and when the charge level has reached about 40 per cent, simply pop the mains adaptor back in again.

The other option is to remove the battery completely, but you should check your notebook's manual as some are designed to be used with the battery in place. If you remove the battery, it's very important not to store it fully charged. Use it until the charge level is between 40 and 50 per cent, and then take it out. This will slow down the deterioration process dramatically. You should keep it somewhere cool, too, as the battery's ageing process is accelerated in hot conditions. You can even put it in the fridge - but not the freezer!

The fact that li-ion batteries can be affected by the notebook being constantly plugged in has led certain manufacturers to include a plugged-in power management mode that uses the battery rather than the main supply some of the time. This gives a constant partial-discharge/charge cycle that keeps the battery in the best condition. If your notebook has this feature, make sure you use it.

You will also find a battery recalibration or conditioning routine in the BIOS setup of many notebooks. As we've seen, li-ion batteries don't need to be fully discharged and recharged to stay in good order. However, the smart electronics in them - which keep track of how much charge has gone into and come out of the battery, and let Windows give you a percentage figure of charge remaining - can become inaccurate over time. So even when the li-ion cells are in good condition, the smart part of the battery pack prematurely reports that they are fully charged and stops the charging process to protect them. The upshot is apparent reduced battery life even though the cells are fine; they're just not being fully charged. To correct this, the reconditioning routine runs the cells flat and completely recharges them so the smart electronics can get their bearings and recalibrate.

Author: David Fearon