Siemens Simatic M7-400 Reference Manual page 35

Battery/Power supply
The batteries used must have the following properties:
• Battery technology: Li/SOCL2
• Model: AA
• Voltage: 3.6 V
The batteries stipulated by Siemens fulfil requirements that go beyond the ones
mentioned above.
You may only use batteries approved by Siemens !
Note
If you do not know the capacity and inductance of the cable, you can use the
following values:
Cc = 197 pF/m (60 pF/ft.), Lc = 0.66 pF/m (0.2 mH/ft)
Example
The battery of type 4022 from Varta together with a 1.5 m long cable and a plug
connection of type 02–02.1500 from Leonhardy meet these conditions.
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
≥
Ca
≥
La
General Technical Specifications
CPU iput "Ext. Batt." incl. cable
Ci + Cc (25nF + Cc)
Li + Lc (2mH + Lc)
1-7