OB81 and baf backup voltage failure on central rack

Hi Every one,

I am working on S7-300 PLC and CPU is 315 2 DP 315-2af03-0ab0/ v1.2.

Total number of racks 3 (1 CPU with IM360 and others are IM361 used).

I am getting error OB81 and baf backup voltage failure on central rack

when i dig the error which says

The 24-V voltage supply

A battery

The complete backup

I refer to CPU Input Power 24V which is ok check with multimeter, i check battery which is 3.3v .

CPU suddenly comes on SF and after some time, sf removes automatically.

when CPU goes on SF dim red light blinks on IM360 module,i replace IM360 module but still same problem, i replace plane connector of CPU same problem.

Some times it shows batt fault but some times dont.

this fault occurs frequently in a day.

I am confused what will be problem?

Please Advise

From your description it sounds like the processor itself. as you are getting a number of different faults and you have changed the connectors, the only other possibility is the Power supply. It definitely sounds like hardware problem.

A question


Does the 315-2DP CPU have a battery?Because you mentioned that you checked the battery & found it 3.3V

hagos said:

A question


Does the 315-2DP CPU have a battery?Because you mentioned that you checked the battery & found it 3.3V

Click to expand...

The 6ES7315-2AF03-0AB0 or eariler CPUs have batteries.

Some times it shows batt fault but some times dont.

this fault occurs frequently in a day.

I am confused what will be problem?

Please Advise

Click to expand...

Replace the battery.