Ever wondered why your portable device's battery doesn't last longer? We explain the technology behind battery power, and provide tips on how to maximise it.The simple fact of notebook life is that systems simply don't run for as long on their batteries as we'd like -- even long-lived notebooks, such as IBM's ThinkPad X31, last only 8 hours on two batteries.
To help you make smart decisions about the notebooks you buy and the way you use them, we demystify today's battery technologies and examine the fuel cell technology that might power your next notebook. We also provide 10 tips for getting the most out of your system's current battery, along with a glossary of key terms.
We can't make a battery last forever, but we can help to make sure that you get the most out of every electron.
Dear reader,
Don't get confused by the descriptions above about the flow of electrons to and from the positive and negative electrodes.
A negative electrode is negative because it carries a surplus of negative charge. As electrons are negatively charged, this means that the negative electrode has an excess of electrons.
Similarly, the positive electrode is positive because it has a lack of electrons - and it is the tendancy of the electrons to move in such a way as to balance this out that causes electric current.
In other words, electrons will flow out of the negative electrode into the external circuit (in this case, the laptop's electonics), through this circuit and into the positive electrode.
The place to which the description refers is from the electrode into the electrolyte - the conductive paste that is between the electrodes inside the battery. Electrons move from the electrolyte onto the negative electrode, and from the positive electrode into the electrolyte.
The direction of flow (from the negative to the positive) is called electron current.
However, because our brains like to think in terms of positives, and because the early experimenters with electricity did not realise that the current was being carried by negatively charged particles, they defined current in terms of flow of positively charged particles from the positive to the negative. This is called conventional current.
A way of visualising this in electron flow is the opposing flow of "holes" into which an electron can move. As an electron moves forwards in the direction of electron current, the (effectively positively charged) hole moves backwards - in the direction of conventional current.
The effect is identical - charge is carried around a circuit through charged particles.