ABB AC 800M

Section 2 Installation Installing the SB821 External Battery Unit
3BSE 027 941 R301 85
Installing the SB821 External Battery Unit
Use the following procedure to connect the external battery unit:
1. Mount the SB821 external battery unit at a suitable position on the DIN-rail.
2. For connecting the SB821 external battery unit, use the 2 m (2.2 yd) cable
TK821V020. Plug one end into the battery unit and the other into the external
battery supply socket of the PM8xx processor unit (see Figure 2 on page 29).
3. In redundant CPU configuration containing two PM861/PM864 processor
units, use also two SB821 battery units, one for each processor unit.
4. Due to the batteries being connected in parallel, it is necessary, when using the
external battery, to remove the internal battery from the PM8xx in order to
avoid reducing available memory back-up time.
Installation of I/O Units
For further information regarding mounting, removing and releasing procedures for
I/O Units, refer to the appropriate I/O system documentation.
Do not connect the TK821V020 cable until the AC 800M Controller has been
powered-up normally and the memory back-up function has been activated. If
no normal power supply is connected to the PM8xx processor unit, the CPU
memory will immediately start to consume battery power when the cable is
connected.
Always install a fresh internal or external battery at the end of the installation
phase. The original battery is heavily utilized due to frequent blackouts during
system installation.