Losing of the user program after power failure

i have CPU S7-400 (6ES7 416-2XK02-0AB0)) with power supply 407 4A ( 6ES7 407-0DA01-0AA0) , and also attach to this PS and external battery to back up the user program in case in power failure 

but after the power failure i discover that the user program is lost and also the hardware configuration despite of the selector in the PS selected on EXT. BATT. and there is no fault appeared on the PS
(5VDC LED) 

the second case i active the OB81 in the user program to indicate if the external battery is low or not and take an effective response to indicate that the battery is low but it loaded to the user program as shown in the attached PDF does this form effect it's response to indicate the fault or not ??

Best regards and many thanks in advance

Hi,

please have a look at this FAQ:

Battery error with the S7-400: OB81 is not called

https://support.industry.siemens.com/cs/ww/en/view/997694

or this: Which organization blocks do you need for error handling in STEP 7 V5.5?

there is an OB81 error handling

https://support.industry.siemens.com/cs/ww/en/view/11499205

Regards,

Towome

Thanks Towome,

but i already load the OB81 in the program and also there is no indication that the battery has any fault ,so what's the cause of this issue ?

thanks in advance