Siemens SIMATIC S7-400 Reference Manual page 59

Power loss
Backup current
Back-up battery (option)
Protective separation in accord‐
ance with IEC 61131-2
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
3.7 Power supply module PS 407 4A (6ES7407-0DA02-0AA0)
20 W
maximum of 100 µA when power off
1 x lithium AA, 3.6 V/2.3 Ah
Yes
Power supply modules
59