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Other Portable Power Sources

In an attempt to provide better maintenance for laptop batteries, manufacturers have developed a new type of battery called the smart battery. Smart batteries tell the computer when they need to be charged, conditioned, or replaced.

The Care and Feeding of Batteries

In general, keep in mind the following basics. First, always store batteries in a cool place. Although a freezer is in concept an excellent storage place, the moisture, metal racks, and food make it a bad idea. Second, use a charger for your Ni-Cd and Ni-MH batteries that also conditions the batteries; they’ll last longer. Third, keep battery contacts clean with a little alcohol or just a dry cloth. Fourth, never handle a battery that has ruptured or broken; battery chemicals are very dangerous. Finally, always recycle old batteries.

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NOTE Got an old portable PC battery lying around? Well, you need to get rid of it, and there are some pretty nasty chemicals in that battery, so you can’t just throw it in the trash. Sooner or later, you’ll probably need to deal with such a battery, so here are some suggestions:

1. Do an online search to find the battery recycling center nearest to you.

2. Sometimes, you can take old laptop batteries to an auto parts store that disposes of old car batteries—I know it sounds odd, but it’s true! See if you can find one in your area that will do this.

3. Many cities offer a hazardous materials disposal or recycling service. Check to see if and how your local government will help you dispose of your old batteries.

Power Management

Many different parts are included in the typical laptop, and each part uses power. The problem with early laptops was that every one of these parts used power continuously, whether or not the system needed that device at that time. For example, the hard drive continued to spin even when it was not being accessed, and the LCD panel continued to display, even when the user walked away from the machine.

The optimal situation would be a system where the user could instruct the PC to shut down unused devices selectively, preferably by defining a maximum period of inactivity that, when reached, would trigger the PC to shut down the inactive device. Longer periods of inactivity would eventually enable the entire system to shut itself down, leaving critical information loaded in RAM, ready to restart if a wake-up event (such as moving the mouse or pressing a key) told the system to restart. The system would have to be sensitive to potential hazards, such as shutting down in the middle of writing to a drive, and so on. Also, this feature could not add significantly to the cost of the PC. Clearly, a machine that could perform these functions would need specialized hardware, BIOS, and operating system to operate properly. This process of cooperation among the hardware, the BIOS, and the OS to reduce power use is known generically as power management.

System Management Mode

Intel began the process of power management with a series of new features built into the 386SX CPU. These new features enabled the CPU to slow down or stop its clock without erasing the register information, as well as enabling power saving in peripherals. These features were collectively called System Management Mode (SMM). All modern CPUs have SMM. Although a power-saving CPU was okay, power management was relegated to special “sleep” or “doze” buttons that would stop the CPU and all of the peripherals on the laptop. To take real advantage of SMM, the system needed a specialized BIOS and OS to go with the SMM CPU. To this end, Intel put forward the Advanced Power Management (APM) specification in 1992 and the Advanced Configuration and Power Interface (ACPI) standard in 1996.

Requirements for APM/ACPI

To function fully, APM and ACPI require a number of items. First is an SMM-capable CPU. As virtually all CPUs are SMM-capable, this is easy. Second is an APM-compliant BIOS that enables the CPU to shut off the peripherals when desired. The third requirement is devices