Siemens SIMATIC S7-400 Reference Manual page 65

3.9 Power supply modules PS 407 10A (6ES7407-0KA02-0AA0) and PS 10A R (6ES7407-0KR02-0AA0)
Back-up batteries (option)
Protective separation in accordance with
IEC 61131-2
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
Power supply modules
2 x lithium AA,
3.6 V/2.3 Ah
Yes
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