5370 CompactLogix (CLX) Memory and power

It looks like the 5370 series CLX devices do not have an internal battery but uses 'energy storage' (I'm assuming a capacitor). In the event of power failure how long would this 'energy storage' last?

I was just told by the support hotline that the 5370 unit stores info in non-volatile memory.

Wouldn't that make the SD card kind of redundant?

From what I understand this is just a fancy way of saying " No more batteries- we will use SD cards now. "

lol

from their website

SD Flash
These units accept SD flash cards that eliminate batteries and provide program storage for auto load of program upon power up. The SD cards can also be used for application/project storage, firmware supervisor, runtime tag data read/write, fault dump during MNRF(Major Non Recoverable Faults). Each controller comes with 1GB SD Card

I can go into depth, but I'll try to stay concise and focus on your controllers.

The 5370 series CompactLogix use a capacitor to store energy for two purposes: to maintain the controller real-time-clock during powerdown, and to run the controller during the power-down sequence.

When you shut off the supply power to a 5370 series CompactLogix, the controller goes through a shut-down sequence that includes writing the current values of the Tag Database to internal nonvolatile memory. This takes longer than just "dump the RAM and re-load the default values later", so it uses a relatively large amount of energy from the capacitor for a few seconds.

After the program and tag database are safely saved to internal nonvolatile memory, the controller settles down and uses just a trickle of current to run the clock backup.

The endurance of the clock backup varies with temperature a little, but in general it's about a month. Knowledgebase document ID 468536 has some details (Access Level: Everyone).

Because the program and tag database values have been saved to flash, they will remain stored indefinitely.

Storing a program on the SD card is different; the controller can load from SD card on powerup depending on how it's been configured (the configuration is stored on the SD card and read at powerup if the card is present).

But the controller always saves its tag database values at powerdown to the onboard nonvolatile memory, not to the SD card.

You're the Forum member trying to get an NMEA signal into your controller, right ?

I am a little excited about this because I've faced a related problem needing to get a consistent, reliable, but only accurate-to-one-second time into CompactLogix controllers that cannot get their time signal from a network or the Internet.

Yeah that is on another project I am working on. I still have yet to test it. Luckily that project was delayed a bit so I have some time in late December to pick it back up.