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System Service
C-4. RESTORING DAMAGED CELLS
When a fully discharged cell is left a week or two in the discharged state, it appears as an open
circuit to a source of charge. This is why a neglected battery pack appears to be fully charged when
an HP 30311A Power Supply is first turned on. The charging current detector sees no charging
current and immediately indicates a fully charged condition. The battery backup capability in this
case is actually non-existent.
Such a cell or battery can be restored if put on a constant-current-limited power supply (0.15 to
0.25 amperes) with the charging voltage set to 150 percent of the normal float voltage. Once the
cell or battery starts accepting a charge, apply 130 to 150 percent of its ampere-hour capacity.
Note that the cells used in the battery for the HP 30311A are rated at 5 ampere-hours.
C-5. SHIPPING BATTERIES
We recommend that the 5-ampere fuse of the HP 30311A Power Supply be removed when the
power supply is shipped or stored. This prevents the battery from discharging if the front panel
power switch is accidentally tripped during handling. (A tripped switch causes the battery to
discharge fully in three or four days.)
C-6. SUMMARY
The HP 30311A Power Supply is designed to power memory and, with its battery backup
capability, to carry the system through AC line power failures and brief maintenance procedures.
If
AC power is interrupted, the HP 30311A can provide backup power for approximately 15 minutes.
A few practical suggestions for improving battery life follow:
•
Avoid exposing batteries to excessive heat or cold for prolonged periods.
•
Never leave a lead-acid cell or battery in a discharged state for longer than absolutely necessary.
•
Disable the power supplies and battery output by setting the LOWER 128K MEMORY and, if
appropriate, the UPPER 128K MEMORY switches to STANDBY if system shutdown will
exceed 15 minutes.
•
Tum off the HP 30311A Power Supplies at their front panel if system shutdown will exceed
four hours.
C-2
JAN 1977
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