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Battery Backup Systems

Battery backup systems protect computer systems from power failures. There are several different types of power failures, including brownouts and blackouts. A brownout is when the power level falls to a lower level and

stays there for several minutes (or longer). This may eventually lead to a blackout, or total loss of power.

Brownouts and blackouts are covered in more detail in Chapter 6, «Network Installation and Upgrades.»

Battery backup systems use a battery to power the computer and its assorted peripherals. Generally speaking, when these devices are activated due to a power failure, they permit the user to save data and initiate a graceful shutdown of the system. They normally aren’t used to run the system for an extended period (unless the units use a very large-capacity battery).

Never plug a laser printer or copier into a battery backup device. These devices draw tremendous amounts of current when they are turned on (much more than any computer or network device would ever draw). If you do this, you could permanently damage or disable your battery backup device.

There are two main types of battery backup systems:

■    Standby Power Supply (SPS)

■    Uninterruptible Power Supply (UPS)

Power output from battery-powered inverters isn’t exactly perfect. Normal power output alternates polarity 60 times a second (60 Hertz). When graphed, this output looks like a sine wave. Output from inverters is stepped to approximate this sine wave output, but it really never duplicates it. Today’s inverter technology can come extremely close, but the differences between inverter and true AC power can cause damage to computer power supplies over the long run.

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