hello everyone.

I'm hoping to clear up something I can't find mentioned in the s7-400 documentation.

It's my understanding that I can supply power to the EXT.-BATT port on the CPU using a 2.5mm jack connected to a voltage of 5-15v and this will keep the data/program in the RAM (no flash memory card) and keep the rack powered up.

In a scenario let's say I have connected a standard 9v battery to the EXT.-BATT port.

from this point my queries are - 

1. If I were to then remove the entire power supply module and 2 batteries to replace it, do I need put the CPU into stop mode or can it be left in RUN during the swap?

2. if it can be left in RUN whilst the swap is carried out, would the operation/automation need to be stopped or will the 9v be enough to keep the rack powered to continue to operate the system without the main power module?

(reason being that if carried out whilst in operation I could avoid site downtime)

I've had a good browse through available documentation but I can't find much detail and don't want to work on assumption.

thanks all

Hi FIVESKIN,

SIMATIC S7-400 S7-400 Automation System, CPU Specifications check the hapter 2.1 

Also check this:

Jack Plug for the supply of an external backup voltage to S7-400 PLCs