Processor losing memory

Has anyone seen this with the following setup and if so is there a fix and what might have caused this. I am posting this for a fellow co-worker at a different site so i don't have much more info than this to offer. What i take is that the processor stayed on until the battery backup power drop below supply voltage level for the plc. Even after this occurred the plc's battery should have kept the program unless it was bad, which they say it never gave a battery alarm. Let me know what you think.

Processor: 1769-L35e running v13 firmware (Compact Logix) – No flash card.

Situation: Power was removed from location to perform work on power center over the weekend. Backup batteries should have kept the PLC online for some time, but it eventually lost power. When power was restored the PLC’s program was completely gone and had Major Processor Fault of “01 Powerup Fault Code 60”. No PLC battery fault was shown, compact flash backup not used. Program was downloaded back into processor and it ran fine all day Monday. The same error occurred this morning with the entire PLC program memory being wiped out again. I’m unsure if the processor lost power last night.

the main question i have is, do you have one battery for the plc or 2?

no, i am not kidding, there are two batteries required for the
logix 5000. i can't remember the details exactly, but we used a logix 5000 years ago and had two batteries. the plc battery is not used to save the plc program, but for something else. the massive battery is long term and keeps the plc program and comments in the plc processor.

regards,
james

I have had problems similar to this where analog devices were pulling down the backplane power supply. Power Supply problems also cause PLC memory loss.

In my case I had a bad analog device, which was most apparent when powering up. After re-downloading the program, it would run fine until powered down again. The inrush of power to the analog device was enough to pull the powersupply down enough that the plc would fault and show the analog card to be missing.