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Battery Power - Part 5

Don Bradbury finalises his look at battery types, their applications, and their maintenance

Notebooks

Notebook batteries can be something of a headache as you'll probably not be able to 'exercise' your battery in quite the same way as I outlined previously. What you have to do instead is periodically run the battery down on the machine itself. I do that, even to the point of letting Windows crash out due to low battery voltage. Then I recharge fully, reboot the machine, and let Windows run Scandisk automatically.

That advice naturally presumes the notebook had nothing running in memory that could be lost at power-down, otherwise it would have been destroyed. It also means a reboot of Windows ahead of the procedure to ensure that no application temp files were on the disk at the time the machine ran out of juice. A bit of a pain, I know, but it's the way to preserve the life of your precious batteries.

Better still, load the notebook to DOS level (via F8 during boot) and let the battery discharge from there. You'll probably not be able to monitor battery capacity while there, but it does the job.

Smart Battery

Nearly all new notebook computers now use battery packs that follow the Smart Battery specification, because battery management is part of the Advanced Configuration and Power Interface that's required for compatibility with the latest versions of Windows. Among other data that the battery can relay are its chemistry, its capacity, its voltage, and even its physical packaging.

Messages warn not only about the current status of the battery's charge but even how many charge-recharge cycles the battery has undergone so the charger can monitor it long-term. Under ACPI, computer manufacturers are allowed the alternative of using either the Smart Battery or the newly introduced Control Method Battery Interface (documented as part of the ACPI standard) for battery management.

Smart Battery provides the hardware interface, an embedded controller with registers that your computer's operating system accesses through its System Management Bus.

Cell chemistries

Ni-MH cells are really just an extension of the nickel-cadmium technology. The difference is the substitution of a hydrogen-absorbing negative electrode for the cadmium-based electrode. This increases the cell capacity at a given weight and volume, and it eliminates the rather nasty Cadmium which raises toxicity issues.

Ni-MH batteries offer high drain capability, which means they will maintain their voltage at a higher current drain than either alkaline or Ni-Cad types. This gives longer service life in applications like digital cameras where high battery drain eats up other battery types.

Lithium batteries offer relatively high energy. In addition, those that have spirally wound large surface electrodes offer a high load capability and low self-discharge rates. Both the lithium battery's longer operating time and its higher cell voltage of 3V are important in camera applications. The latest generation of cameras with numerous automatic functions, which necessitates increased energy demand and relatively high load requirements, means Lithium batteries are a particularly good choice for today's cameras.

In conclusion

I hope my brief summary of the present state of battery technology and their dedicated chargers will have done something to stimulate your interest in the subject and aid you in your desire to maintain your life-giving cells properly. Look after your batteries, whatever they are used for, and they will look after you. Neglect them and you do so at your peril!