Honeywell HPM, Service

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6 Removal and Replacement
6.13 48 V Backup Battery Replacement
R688 HPM High-Performance Process Manager Service 427
December 2020 Honeywell

Batteries should not be left in a discharged condition for extended periods of time, as this strongly
affects the ability of the battery to accept a charge thereafter. The batteries should be charged
periodically if they are stored or in an nonpowered system.

The HPM provides proper charging current to the batteries while the subsystem is powered up and
running. Whenever ac power is removed from the subsystem, the Power System automatically
draws power from the batteries to maintain the subsystem’s 24 Vdc power. Anytime the system is
intentionally shutdown and left nonpowered, the
BATTERY switch at the front of the Power
System assembly should be placed in the
OFF
position to prevent discharge of the batteries.

Service life is directly reduced by high ambient temperature. Heat destroys batteries. While the
operating temperature range is -15 degrees C to 50 degrees C, maximum service life will be realized
when the batteries are operated in an ambient of 20 degrees C. Brief usage, that is, a few days, at
higher temperatures will have no adverse effect on the service life. However, if such usage is over
extended periods of time or occurs repetitively (such as a environment that is not air-conditioned),
the service life will be reduced. This reduction may be as much as 20% of service life (1 year) for
each 10 degrees C above the reference ambient of 20 degrees C.
48 V Battery Pack service life

Service life is reduced by the number of discharges and the depth of each discharge. The batteries
can provide 200 cycles at 100% depth of discharge, 550 cycles at 50% depth of discharge, 1200
cycles at 30% depth of discharge, or 2000 cycles at 10% depth of discharge. This effect is
superimposed on the standby aging effect stated above.

With an expected 5 year life, 200 cycles would represent one power outage approximately every 9
days, or approximately 2000 ampere-hours of 24 Vdc subsystem backup.
Battery charge voltage check procedure
Use the procedure in the following table to verify that the output voltage to the 48 Volt Battery Pack is
proper.
Step Action
1 Locate the test points marked " COMMON " (-) and " BATTERY " (+) at the front of the
primary Power Supply Module and connect a dc voltmeter with an accuracy of +/- 0.05
volts across the test points.
2 The voltage should read between 54.0 volts minimum to 55.2 volts maximum at 20
degrees C. For each degree the battery enclosure temperature deviates from 20
degrees C, the f
ollowing adjustments in Power Supply Module’s battery charge output
voltage are applicable.
Above 20 degrees C, the battery charge voltage limits are decreased by 72 mv/deg C.
Below 20 degrees C, the battery charge voltage limits are increased by 72 mv/deg C.
If the charge voltage is outside of these limits, replace the module.
3
This step and step 5 should be performed during plant shutdowns since it requires
disconnecting the battery pack and placing the redundant Power Supply Module’s
power switch in the
OFF position.
Disconnect the battery pack. With the voltmeter connected to the primary Power Supply
Module’s battery test points, place the redundant Power Supply Module’s power switch
in the
OFF position. The voltage should not fall below the minimum voltage specified in
step 3. If it does, replace the redundant Power Supply Module.
4
Place the redundant Power Supply Module’s power switch in the
ON position. Move the
test leads to the battery test points on the redundant Power Supply Module and place
the primary Power Supply Module’s power switch in the
OFF position. The voltage
should not fall below the minimum voltage specified in step 3. If it does, replace the
redundant Power Supply Module.
5 Reconnect the battery pack to the Power System.