SLC battery life

[Skidood]

Hi group, just wondering if anyone has knowledge of how long the CPU module battery can be expected to last before throwing the LED. The machine in question is turned off 90% of the time. TIA.

 

[James Mcquade]

it depends on how good the battery is when you install it.
it also depends on how good the internal capacitor is on the plc should the battery fail. temperature will also change things.

before you turn the power off, you need to get a good backup of the program in the plc ! the plc program is the master, the hard drive copy is just in case,
bubba loves to make changes and not tell people. Learned that the hard way.

we changed the battery every year in our systems as part of our operating procedure.

james

 

[geniusintraining]

The machine in question is turned off 90% of the time.

Thats a lot of time... I had a controllogix that I ran a dedicated power to the PLC, if they turn off the power or hit a e-stop the control power to everything was shut off but the PLC would still stay up (not the I/O) and it worked out great

 

[Rob...]

Correct me if I'm wrong, but I believe those batteries do not re charge when powered up.

So as soon as it's installed it's draining.

As for life span, I couldn't say. Most factories I visit have a PM schedule for around a year to change them.

 

[geniusintraining]

Correct me if I'm wrong, but I believe those batteries do not re charge when powered up.

So as soon as it's installed it's draining.

As for life span, I couldn't say. Most factories I visit have a PM schedule for around a year to change them.

You are correct... I wondered why they did not do just that you would of thought just a rechargeable battery would of been nice. I know they are moving to the micro flash now but even when the ControlLogix came out I had a large program that would last about 24 hrs powered off before the battery was dead, I do know on them it would depend on the size of the program, a second machine would last about a week

 

[parky]

If the PLC is powered up most of the time then the battery will normally last 5-10 years. The battery on most PLC's only drain when PLC is powered down, but I have been in this game for about 40 years and I suggest the longest time before battery replacement is about 3 years. However many of the customers I have done work for like the battery to be changed once a year.
On another matter I know you are supposed to power down before replacing the battery but I have been called to many a system where the battery warning light is on, as some of these were either in constant production or we did not have a copy of the code (Other OEM locked) I have changed the battery while live without ever having a problem. As in general there is a diode in the line the battery voltage is slightly lower than the power supplied to the backed up ram so effectively the battery supply is blocked while under power.