DO PLC Batteries Recharge?

We have lots of SLC controllers and some control logix type. We replace the CPU bettery once a year as a PM. Is this still good practice?

If we have a machine down for an extended time to the point that the battery does not hold the program does the battery need to be changed when we reload the program or will it recharge once the PLC is powered up?

If the battery is replaceable, it most likely is not rechargable.
Once per year is excessive.
Lithium batteries have a 10 year life, even if they aren't being used. I would go with 3 or 5 year.

Most processors have a capacitor back-up that provides memory back-up of 5-30 days after the power has been removed. Before removing the battery from a stored unit. Connect power to it so the capacitor will charge. This will prevent the loss of the program.
I agree with keithkyll. The battery is not rechargable. We usually go with a 5 year program.

Regards,
Garry
http://www.accautomation.ca

+1 for gclshortt , I would add that a 1 year swap-out is worth it if the PLC is unpowered .

Check with Industrial Concepts at the link below before buying your batteries also.

http://www.plccable.com/plc-cpu-batteries/

I did not see that Mark sold these batteries until after I purchased 15 of them from my AB dist.
AB thinks a lot of their batteries, we paid way to much.

BCS

Use a processor's "low battery" minor fault as a signal to get it changed...

You will get plenty of fore-warning, as the low battery status is very early. Depending on usage, you will get weeks or months of useful life from a battery that is flagged as "low".

Now let us quantify "depending on usage"...

SLC and early ControlLogix processors (up to and including the 1756-L5x series) "use" the battery power to retain the memory all the time the power is off.

1756-L6x series ControlLogix processors "use" the power from the battery to transfer the volatile memory to non-volatile (flash) memory when the power goes off.

1756-L7x series processors do not have a battery, but use an "energy storage module" which is charged continuously, and the energy is used as per the L6x series.

Taking that into consideration, SLC and L5x processors that are turned off for long periods will require battery changes more frequently. An L6x series processor will require more frequent battery changes the more times the power is turned off, irrespective of how long the power is off.

Bering C Sparky said:

Check with Industrial Concepts at the link below before buying your batteries also.

http://www.plccable.com/plc-cpu-batteries/

I did not see that Mark sold these batteries until after I purchased 15 of them from my AB dist.
AB thinks a lot of their batteries, we paid way to much.

BCS

Click to expand...

Thanks for the plug.... BCS

I do have a LOT of customers that order the same thing every year... most in November and when they shut down for the holiday they replace them all

Not just because I sell them I do think its a good idea, it will only few seconds and 20 bucks to replace a battery, at the same time I would upload the program, I did this for all my "critical" processes

It was a lot cheaper then having a machine down for a few hours during the off shifts

On the other hand.... I HAVE A LOT of customers call and say they need a battery sent overnight and they did not have a back up of the program

The older 1756 are battery killers... I had one that would kill a battery in a day with no power, I ran a dedicated power to the CPU and keep the CPU powered up

daba said:

......1756-L6x series ControlLogix processors "use" the power from the battery to transfer the volatile memory to non-volatile (flash) memory when the power goes off.

Click to expand...

Just to clarify, that is only the case if the optional CompactFlash is installed, AND it is a Series B unit where the CompactFlash is on the front of the module. The Series A does not do this. Without the optional CompactFlash it uses the battery to keep the RAM intact.

I would also refer to it as the "external CompactFlash" where on the L7x I would call it "flash memory". People sometimes confuse the "flash" memory with the removable SD card on the L7x. that L7x has RAM, flash, and an SD card. Three things instead of the two on the L6x (RAM, optional "external CompactFlash").

OG

I know the User Manual for the ControlLogix series has a chart for recommended replacement vs. ambient temperature. I assume the SLC is probably similar.

≤35°C never
≤40°C 3 years
≤45°C 2 years
≤50°C 16 months
≤55°C 11 months
≤70°C 8 months

It also depends of course on how risk averse you are and what other measures are in place for a quick recovery.

Our PLC runs off a generator-backed UPS feed; ambient temperature is about 20°C; and I have software, equipment, and qualified personnel on site to upload programs in the event of failure.

On the other hand batteries are cheap (comparatively).