Feature: How to look after your laptop battery

Exploding laptop batteries might make good headlines and video clips, but the recent spate of battery recalls involving defective Sony lithium-ion (Li-Ion) batteries fitted in several top-name notebook makers will not make the average notebook owner very happy.

The thought of a laptop spontaneously going up in flames while unattended in an office, car or home is enough to give anyone sleepless nights. But assuming you’re not one of those affected by the recall, is there any reason to worry, or are there any precautions you should take?

A bundle of portable power
Rechargeable Li-Ion battery cells have been around since about 1991 and made truly portable computing a reality. Li-Ion chemistry is widely regarded as one of the safest battery technologies for consumer devices.

They have good performance, are cheap and lightweight. They don’t suffer from ‘memory’ effects and don’t need charging maintenance cycles. But on the downside, they need complex charging and protection circuits to prevent them becoming unsafe. Plus, always remember that batteries are powerful capsules of electrochemical energy, and should be treated with respect.

Battery packs are robust, but are certainly not immune to bad care and handling. For example, dropping a battery pack can damage the casing or internals, or in severe cases cause it to catch fire. A battery that’s suffered a hard fall shouldn’t be trusted, but replaced.

Also, don’t let a battery become too hot, for example by leaving your laptop on the passenger shelf of a car. Overheating can degrade the battery’s performance and lifespan, or in extreme cases cause it to fail violently. When using your laptop on the move, keep all the vent holes clear to prevent build-up of internal heat.

But there are some myths still associated with Li-Ion batteries. One is that constantly ‘topping’ up the battery can damage it – this isn’t true. The reason, according to Motorola’s website (see link below) is that relationship between depth of discharge and number of charging cycles is logarithmic, not linear.

In simple terms this means that a battery rated for 300 full discharge cycles will actually be able to last several thousand shallow discharge cycles: if this wasn’t the case, simply plugging in your laptop 300 times would be enough to ruin your battery.

However, if you mostly use your laptop on mains power, there’s no harm in removing the battery and storing it safely. According to battery specialists Cadex Electronics, Li-Ion batteries should ideally be stored at below 15ºC and at about 40-50 per cent charge level.

Links to battery technical information
www.buchmann.ca – Cadex Electronics
www.powerstream.com/tech.html – Lots of technical info on different battery types
www.motorola.com/testservices/article1.htm – Motorola’s power testing labs

This article is part of a group test of budget Core 2 Duo notebooks .
See also: Asus F3Jv, Evesham Voyager C530, Hi-grade Notino D7000-5500, HP Compaq NX7400 (RH393ET), MSI Megabook M662, Rock Pegasus 665-T56, Sony VGN-C1Z/B