applecruncher1

Siemens S5-95U PLC and Battery Concern

4 posts in this topic

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,

 

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The picture shows you have an EEPROM inserted so no battery is required - the PLC will reload the program after every "power on".

Although the battery maybe needed to maintain any user / machine data that maybe adjusted form an HMI?

If you have changed the battery and the LED is still on then you either have a faulty battery, wrongly connected battery, bad connected battery or a fault PLC.

Have you the S5 software to go online and check the I & B Stacks when the PLC faults ??

 

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Hi,

I apologize for the late reply as I have been busy lately.  

We require the battery as the program in the RAM has machine data and modifications that does not exist in the EEPROM. 

That said, it is quite difficult to catch the error with the I & B stack as the stops happen instantaneously such that by the time I open the I & B stacks the PLC is back to RUN status. Is there other ways to confirm whether this is a software or hardware fault?

 

Thanks,

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If the program is on RAM then remove the EPROM and see if the program remains in RAM after the power is removed (make a back up first).

If the program is still in the RAM then the battery is good - it is the "detection " circuit in the PLC that is faulty.

I would either replace the PLC for a reconditioned unit OR replace the entire system for an S7 1200 PLC.

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