IBM Storwize V7000 Troubleshooting And Maintenance Manual page 45

v A battery has been powered on for three months without a maintenance
discharge.
v A battery has provided protection for saving critical data at least twice.
v A battery has provided protection for at least 10 brown outs, which lasted up to
10 seconds each.
A maintenance discharge takes approximately 10 hours to complete. If the ac
power outage occurs during the maintenance cycle, the cycle must be restarted.
The cycle is scheduled automatically when the battery is fully charged.
Under the following conditions, a battery is not considered when calculating
whether there is sufficient charge to protect the system. This condition persists
until a maintenance discharge cycle is completed.
v A battery is performing a maintenance discharge.
v A battery has provided protection for saving critical data at least four times
without any intervening maintenance discharge.
v A battery has provided protection for at least 20 brown outs, which lasted up to
10 seconds each.
v A battery must restart a maintenance discharge because the previous
maintenance cycle was disrupted by an ac power outage.
If a system suffers repeated ac power failures without a sufficient time interval in
between the ac failures to complete battery conditioning, then neither battery is
considered when calculating whether there is sufficient charge to protect the
system. In these circumstances, the system enters service state and does not permit
I/O operations to be restarted until the batteries have charged and one of the
batteries has completed a maintenance discharge. This activity takes approximately
10 hours.
If one of the batteries in a system fails and is not replaced, it prevents the other
battery from performing a maintenance discharge. Not only does this condition
reduce the lifetime of the remaining battery, but it also prevents a maintenance
discharge cycle from occurring after the battery has provided protection for at least
2 critical saves or 10 brown outs. Preventing this maintenance cycle from occurring
increases the risk that the system accumulates a sufficient number of power
outages to cause the remaining battery to be discounted when calculating whether
there is sufficient charge to protect the system. This condition results in the system
entering service state while the one remaining battery performs a maintenance
discharge. I/O operations are not permitted during this process. This activity takes
approximately 10 hours.
Chapter 3. Understanding the Storwize V7000 battery operation for the control enclosure
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