hi experts

if the battery in cpu 300 or 400 fails what will happen?i want to know if cpu goes to stop mode?

thx

hello 

first , Battery fault indication shows in power supply

second , we can used specific OB for battery can be used in PLC logic (OB81) 

and in case of battery problem the system run normally (if you don't use in OB1), you may have risk of program erasing if we don't have memory.

thanks

Hello,

and check this:

 https://support.industry.siemens.com/cs/document/9306918/when-should-you-replace-the-back-up-battery-on-your-s7-300-400-controller?lc=en-ww

and never change battery with power OFF

 https://support.industry.siemens.com/cs/ww/en/view/17900782

 http://support.automation.siemens.com/WW/view/en/7701820

hamed12580

hi experts

if the battery in cpu 300 or 400 fails what will happen?i want to know if cpu goes to stop mode?

thx

 Hello Dear Hamed

In loss or low battery mode (CPU 400), first BATT LED and then BAF LED on the CPU will be on. At the same time (as the BAF LED), OB81 is executed.

*** OB81 is related to Power supply error (like low or loss battery). If this block not downloaded on the CPU, the Battery fault causes the system to stop.