Battery Low alarm dont go off in PLC 5/40E

[AB2005]

Dear Colleagues,

I have a PLC 5/40E in one of our machine. An alarm message “PLC Battery Low” appeared at HMI. I checked the battery and found exact 3V. However I replaced it with a new one. When I plugged inn the battery, Battery low indication on PLC did not OFF. I cycled the power and found that LED OFF and error message removed but after some time, it again appeared and has not been removing yet while battery was OK. Can any body help me out? I think problem is in PLC not in battery

 

[OkiePC]

I have seen the little plug on the PLC become damaged and create an intermittent connection, so this is something to check.

 

[AB2005]

But say if it is damaged, then alarm should not disappear when we cycle the power. After cycling the power, alarm disappears and appears after passage of some time.

 

[mellis]

Another possiblity...

The battery you replaced it with was just as old. The service life of the lithium cells in PLC5s is about the same as the shelf life.

 

[Ron Beaufort]

I checked the battery and found exact 3V.

just checking ANY battery for "voltage" in an open circuit is an inconclusive test ... the battery must have a "load" applied to it - or even an ALMOST "dead" one will read the proper voltage ...

 

[AB2005]

I have checked the plug of battery and found ok.
I confirmed the problem by replacing the battery with another new one and found the same results. During battery connected, voltage measured and found 3V.