plc battery checking

There is no way to check the PLC battery validity. The only things that you can do, is to record the date and time, when you last replace the battery. The battery need to be replace within every 2 years.

When you replace the PLC battery, you got to do it while the PLC is power up otherwise you will loss all the program if you replace the PLC battery with power shut down.

As long as the power supply is "ON" your PLC will be working fine without the battery. But don't take the risk.

thanks for your reply.

can u send me a link that give more elaboration about plc hardware ,internal strucure, the common preventive maintenance for plc?

Simply place the battery on planned preventative maintenance schedules.

• Ooooh! How about running a timer within the code that starts when a new battery is installed, and when expired in, say, 2 years raises an alarm on the human-machine interface?

Just had a customer find out after he shut down a production machine for 3 months (slowdown in sales). When he did try to start it up no go!

Battery dead, plc lost the whole program!

We were able to locate a backup copy (5 1/4 floppy drive) with some version of the machine program on it, but to find Modicom 984 programinng software and a Windows 98 or earlier laptop took some work.

Program has been installed and debug being done this week. The boss was P.O.'d to no end because a $12.00 battery was not replaced! You want to be sure to replace the battery every 2-3 years. Think of how long your laptop battery preforms and you get the idea.

Software, legacy laptops, cables, current machine programs etc. are also things to have on hand. Good Luck

That too bad. The person incharge should know better what is the procedure to be taken during the plant shut down.

We also had plant shut down for a few month but the power supply still maintain to all the PLC and other control equipment. We always backup all the PLC programs every month for the latest version available.

The battery inside the PLC is use to help you to maintain the PLC program, if there is some power failure, that last for a few hours. It does not help you to maintain the PLC program for 3 month long. No battery can stand for that long period.

Some of the PLC program are store inside the RAM so that we can do some modification on the programs on line. RAM need battery to be back up all the time for the program.

Of course, you can program all your PLC program in to your Eprom but if you do so, you cannot change or modified any program on line.

It is depend on manufacturer .In catalogs manufacturer explain about life of battery. You do not mention a manufacture of your PLC. If your PLC is Siemens that you just on power of PLC remove old battery and insert new one. Life of battery is 3 to 5 years.

On most PLC's I've ever worked on, there's normally a battery alarm indicator on the CPU. Also there's also an internal bit that turns on when this indicator is on. From this you could bring up an alarm on your HMI (if you have one), or to an output and an external indicator, to inform you the battery needs replacing.

Even if you have a new battery, with all power off, they will probably last no more than 3 months anyway.

hi ,

some PLC have one Indication light (Siemens ) when Battery is low he lit up . Othr wise you check Battery voltage. some time voltage show is ok but when you battery insert in plc it is not work. so you battery out & check battery voltage on load & this time voltage measure if voltage dropp so battery change. When you replace the PLC battery, you sure PLC is power up otherwise you will loss all the program if you replace the PLC battery with power shut down.

As long as the power supply is "ON" your PLC will be working fine without the battery. But don't take the risk.

I'll have to say locate and read the PLC maintenance manual.

As you propably know modern plc´s like Modicon M340 has no battery.

some older plc´s with batteries for their internal memory can also start up the program from a memory card even if they have a broken battery and the power goes of. But some of the older memory cards also have battery that needs to replace.

The RSLogix 5000's that we use have an indicator on the plc controller card and we have that sync'd to an output to the HMI as well. We also have replaced the standard batteries with larger external ones. For extended shutdowns we ensure the the plc has 120vac supplied to prevent programming loss.