Siemens S5-95U PLC Stops Randomly then Runs again and Battery Concern

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Hi All,

We have a hydraulic press that is being controlled by Siemens S5-95U PLC . Lately the S5-95U has been randomly stopping during operation thus causing the hydraulic press to stop running. However the S5-95U instantly returns to RUN status after stopping. This is the first time it has happened after a decade of service.

Prior to the random stops issue, around January 2021 the S5-95U completely stopped and the program in the RAM was erased so we had to replace the PLC battery and restore the program with our backup. Strangely, the PLC battery we replaced still had 3.4VDC upon checking. What's even more baffling is that even after we replaced the PLC battery with a new one,  Battery LED is still yellow although the program is still retained in the RAM.

In summary, we have two concerns:

1. S5-95U randomly stops and resumes during operation ever since we were forced to replace the PLC battery and restore the program.

2. PLC battery has been replaced but the Battery LED is still yellow but the program is still retained in the RAM.

 

I have a suspicion that the two concerns I mentioned above are somehow connected but I lack the technical expertise to diagnose. I'm hoping someone can help me figure out our issue. Worst case, I think our S5-95U needs to be replaced.

 

Thanks,