Backup Battery/Accumulator; Using A Backup Battery Or Accumulator - Siemens SIMATIC S7-300 Series Reference Manual

1.1.3

Backup battery/accumulator

Exceptions
The CPUs 312IFM and 313 do not have a real time clock so they do not need an
accumulator battery.
The CPU 312IFM does not have a buffer which means that you can not insert a
battery.
Backup battery or rechargeable battery?
Table 1-2 shows the differences in the backup provided by an accumulator and a
backup battery.
Table 1-2

Using a Backup Battery or Accumulator

Backup ... Backs up
with...
Rechargea Real-time clock only
ble battery
S
Backup User program (if not
battery stored on memory card
and protected against loss
on power failure)
S
More data areas in data
blocks are to be retained
than possible without
battery
S
The real-time clock
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01
Remarks
The rechargeable battery is charged
after CPU POWER ON.
Note
You must create a backup of the
user program either on Memory
Card or, in the case of CPU314IFM
314 (-5AE0x-), on EPROM.
Note
The >CPU can retain part of the
data without backup battery. You
only need a backup battery if you
want to retain more data than this.
CPUs
Backup
Time
120 h
(at 25_C)
60 h
(at 60_C)
... after 1
hour of
recharging
1 year
1-5