Dell IP4700 Service Guide - Page 92

the battery may require more time to charge

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The Standby Power Supply (SPS) 4 Front Rear Mounting tray with standby power supplies (behind bezel) Standby power supply A Standby power supply B EMC1691 Figure 4-2 Rackmount Installation, Front and Back Views, with IP4700 In the event of a power failure, an SPS provides backup power until the storage processor has flushed its write cache data to the IP4700 or DAE disks. The storage processor then shuts the SPS power off. If the cache flush has not completed within 90 seconds - more than enough time to flush a full cache - or if the storage processor has failed, then the SPS shuts itself down to prevent deep discharge. If there is no ac inlet power and the SPS is shut down, all status lights will be off. When power returns, the SPS starts recharging. It may reach a state of full charge relatively quickly. If power remains off for a long period - days or weeks - the battery may require more time to charge fully. The recharge times are explained in Appendix A. The storage processor will not use the write cache unless it detects at least one fully charged SPS. Battery lifetime depends on the number of discharge cycles and depth of discharge. In a typical environment, a battery pack can last 3 to 5 years. Battery pack lifetime is shorter in locations that have frequent ac outages. 4-4 IP4700 Installation and Service Guide

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4
4-4
IP4700 Installation and Service Guide
The Standby Power Supply (SPS)
Figure 4-2
Rackmount Installation, Front and Back Views, with IP4700
In the event of a power failure, an SPS provides backup power until
the storage processor has flushed its write cache data to the IP4700 or
DAE disks. The storage processor then shuts the SPS power off. If the
cache flush has not completed within 90 seconds
—
more than
enough time to flush a full cache
—
or if the storage processor has
failed, then the SPS shuts itself down to prevent deep discharge. If
there is no ac inlet power and the SPS is shut down, all status lights
will be off.
When power returns, the SPS starts recharging. It may reach a state of
full charge relatively quickly. If power remains off for a long period
—
days or weeks
—
the battery may require more time to charge
fully. The recharge times are explained in Appendix A. The storage
processor will not use the write cache unless it detects at least one
fully charged SPS.
Battery lifetime depends on the number of discharge cycles and
depth of discharge. In a typical environment, a battery pack can last 3
to 5 years. Battery pack lifetime is shorter in locations that have
frequent ac outages.
Rear
EMC1691
Front
Standby power
supply A
Standby power
supply B
Mounting tray with
standby power supplies
(behind bezel)