Control Logix losing program

Anybody ever seen a Control LOgix L55/A CPU lose it's program? The battery went dead (had a BAT LED) and I replaced it. The BAT LED went out but it still loses its program when I power down. I replaced another battery from a known good working CPU and it still doesn't retain it's program.

Is there some bit setting that I am missing?

The batteries for these are only good for microseconds. OK, it's not that bad but the battery times are pretty low, if I recall, measured in minutes. It could be that when these processors where put in the programmer immediately plugged in the battery. During testing and commissioning the processor could have been powered down several times which shortens the battery lifetime.

There is a battery module which provides more battery life (1756-BATM I think). Also you could buy a new battery to be certain.

Incidentally, this apparently isn't an issue with the new L6x processors.

There was also a bug where if you power cycled the plc quickly you could loose the program!!

Thanks for the replies.

My losing the program isn't just a one time thing. Now I am unable to keep the program at all in this CPU. I've put multiple batteries in it now and it still does not keep the program.
I am not cycling the power very fast either. I can power down. Wait 3 seconds, power up, and the program is bye-bye.

I don't think it could be something like a broken connector to the battery either. If I disconnect the battery, BAT LED comes on. Plug it back in, BAT LED goes off.

Weird...

I've had similar problems with the batteries in the control logix processors....Our platen mounted robots have all had to have their batteries replaced, and I think AB has an updated battery with a longer life cycle...of course our guys just order the battery from the robot manufactor...sigh
Let me do some searching and see what I can come up with.

Yeah I just did a quick search and found that you can either use an externally mounted battery which is the 1756-BATM which depending on which particular model you have ranges in life from 133-199 days. The 1756-BA1 is only good for upto 63 days.

Hope this helps!!!
its towards the bottom of the page..
http://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1756-sg001_-en-p.pdf

This may be a warning of worse things to come. Twelve years ago I saw a similar thing happen on a PLC5; battery wouldn't hold up. Turned out to be a RAM chip going bad and the processor faulted supposably costing a electrician a couple of fingers in a conveyor. End result was the PLC was replaced and the electrican couldn't count to ten.

Or it may not.

I agree, this doesn't sound so much like a battery issue as a processor issue.

The battery life times listed in this thread are a bit deceiving. I have several Logix55xx style processors that have had batteries lasting a couple years or more. These are systems that are not powered up 24/7. It depends on how much memory, environmental conditions, and how long and often the system is powered down.

The 63 days quoted above is how long an L55 processor at 25 degrees C will maintain a program when powered down 100% of the time. This is not a case of "you get to buy a new battery every 63 days".

In RSLogix5000 go to Help=>Online Books==>ControlLogix Manuals. Select the ControlLogix System User Manual and look at page 405 (25-3) for a table that shows a battery life estimation tool. The one mentioned above is worst case only, which is also part of the manual I mentioned.

Try your batteries in another processor, try another processor. The battery appears to be the symptom, not the cause.

OG

I'm 99.9% certain that it is not the battery. I've played swap around with the batteries and another processor and the batteries work fine in another processor.

I'm rapidly reaching the conclusion that there is a problem with the processor.

I was just hoping to find a 'magic bullet', such as a bit that needs to be reset, etc...

Thanks.

Now that I think about it, I believe there was a PSA for the L55 processors a while back. If I remember it was something about them having a memory error and clearing their memory. It was a wierd combination of things that triggered it like you had to stand on one foot, hop up and down, hold your left hand with three fingers extended above your head, close one eye and pick your nose (or something like that) and it would fault. I just did an upgrade for a customer a while back that involved changing their L55s to L63s because of this potential. I did a quick search on the knowledge base but didn't find anything. I'd give tech support a call as they'd be able to pull up the details.

As recomended in earlier posts, you should call techsupport to do troubleshooting.
Most likely you are having issue not related to the battery:
Logix (as well as PLC5) processors will erase program if firmware determined that it is not safe to keep program any longer.
Many different reasons why processor will do it.
This is done by design: it is safe state to have no program instead of unstable/corrupted program or faulty hardware.
In some cases fault log can be extracted from the processor - call techsupport.
Before calling make sure you have:
- OK and RS232 LED status after memory loss
- FW rev of your processor and communication modules.

What Software / firmware version are you running. I vaguely remember something like this happening in version 11 early in its release history.

Are you running firmware version 11? One of the early version 11 releases had a bug where it would loose the program on a power failure even if you had a good battery. Rockwell issued a product advisory about this, with the fix being to upgrade to a newer firmware version.

We just had a presentation on this while we were attempting to choose which controller we were going to use.

The AB rep mentioned all of this as a known problem and then went on to describe what the problem actually was. I'm not going to even attempt to describe that presentation.
Moral of the story was that if we wanted to use the L55 then use the BATM battery (looks like a cube with a tether to connect to the battery terminal on the controller). We chose to go with the L63.

Oakley said:

...We chose to go with the L63.

Click to expand...

You definately should look at L63 ser B processor - it uses internal flash memory to save RAM during shutdown and not using battery to hold RAM. Battery will last much longer.

Also L6x processors are much better with memory loss issue compare to L55s.