I have a 1769-L33ER powered by a 1769-PA2 receiving 230v at the source.
Periodically the PLC is losing its program and then the team has to download a backup copy of the program.
I am trying to decide what the most likely culprit is in this situation. Either the PLC (running 33.011) is bad, the 1769-PA2 is not enough power or bad, or the plant has some brownout that is enough to kill the program.
My options are
Get a battery backup power source to take over during this supposed brownout.
Maybe try replacing the lithium battery that the manual says it has
The 1769-L23x and 1769-L3x controllers come with one 1769-BA lithium battery.
The 1768 controllers and the CompactLogix 5370 controllers do not require a battery. The controller uses internal
nonvolatile memory to store its program during shutdown. Energy that is stored in the system maintains controller
power long enough to store the program to internal nonvolatile memory, but not the external CompactFlash card nor SD
card respectively.
My first suspicion would be that the battery is either bad or missing, and the controller is loosing power for some reason.
Depending on the likely hood of change to the program, you can also store the program to an SD card and set up the controller to load the program from SD at power up. The only thing about that is that you have to remember to update the SD card anytime changes are made.
With that information I too would believe it unlikely to be a battery issue, but never know how old the battery is from the factory. Pretty easy to change one, and cant hurt. Then you know for sure that it isn't the battery. Might also want to make sure that it's connected correctly to the controller.
How many other cards are in the rack? How many cards between the PA2 and the controller? How many cards after the PA2 prior to the end cap or another Power supply? What type of cards are they?
In my experience, the issue is usually related to firmware, however, being a newer version I would say probably not. Next is power supply issues, spikes. For example, nearby welding and poor grounding can cause problems. I would replace the power supply and check grounds. Also, being CpLX check all bus connections, perhaps disconnect and reseat all bus connections.
I've got that issue on multiple processor type with firmware 32. After upgrading to V34 the problem was solved and is running for -+ 2years without issues