PM864 Losing Memory after power loss
Everytime their is a power drain or power loss to the controller we have to redownload the program to that particular PM864 .. does anyone have any suggestions as to what would cause this? They are operating in redundancy mode (dual) and i have run them each as primary this did not change anything.
Doesnt show battery alarm on PM864 have changed batteries anyway to new ones and also tested, the batteries seem fine.. we have no UPS connected as it is faulty i will be replacing with a temporary one for now but this still does not resolve the memory loss issue.
Looks like your internal battery (Built-in battery back-up of memory) needs replacement.
Frequency -Every 2 Years PM8xx Internal Battery (if fitted) Change battery
The internal battery is mounted inside the PM8xx processor unit (except PM891). Since the battery is not rechargeable, it is important to exchange it on a regular basis (refer to the Maintenance Frequency Schedule for further details)
3BSE036351-510_en_AC_800M_5.1_Controller_HardwareSection 5 Maintenance -Replacing the Battery
Since you say you have already changed the internal batteries, then its more likely you have a problem with the battery connections. Try some contact cleaner and make sure everything looks clean. Also, there may be some settings that control how the controller reacts after a crash that could also affect a start after a power upset. Check these using the IPConfig tool.
In any case, as others have already said, the internal batteries are very unreliable ( IMHO they are junk) and an external battery is strongly recommended. Your other alternative is to load the application onto a CF card. This works very well if the plant is commissioned and the application is not being changed very often.