If the battery backup fails on a PLC, what will occur? And then it was not replaced?

What is the purpose of PLC battery?

The importance of the battery is to maintain the memory in PLC

Real Time Clock, PLC configuration, PLC Logic, and Process set points are stored in the EPROM (EPROM-Erasable Programmable Read-Only Memory) and EPROM is it powered by the battery. This battery continues to power the EPROM when any power failure or power isolated due to any maintenance. This battery also is known as back up battery, CMOS battery, RAM memory battery, processor battery or RTC battery.

Note: PROM (programmable read-only memory) device installed PLC system is able to run without the battery. The disadvantages are the information is not stored automatically. The programs are stored by external programming device each time settings or made be changes on the system

If the battery backup fails on a PLC, what will occur? And then it was not replaced?

PLC batteries are not rechargeable. However, the system can continue to operate with a bad battery, if a power failure occurs once then the programs will be lost which is stored in EPROM, hence the program settings back to its factory settings. The system will be out of service due to the PLC battery failure. For the same reason, the PLC battery replaces preventive maintenance that should be performed as per manufacturer instruction and schedule.

How will you know if the battery is low or it needs to be replaced?

The low battery LED on the PLC module lights when the battery is low.

The disadvantage of this method is the low battery LED might not be easily seen when the PLC modules are fitted in an enclosure.

Best method is checked by the PMS schedule.

When you have to change the PLC battery?

The PLC battery has to replace by manufacturer guidelines.

Normally the PLC battery needs to be changed every two years

What are the factors affecting the PLC battery life?

• High temperature is to reduce the PLC battery life.
• Frequently power failure
• The system powered off for long durations

How to change the PLC battery?

The PLC battery should be replaced when the PLC module is power ON condition to avoid the chances of losing the contents of EPROM memory.

The PLC should be replaced by manufacturer instructions.

The PLC memory backup module

This used for when PLC is malfunctioning or corrupted PLC program. Make sure PLC memory back up module available for critical machinery like boiler, mooring winches system, steering gear system, etc.

What is the voltage of the PLC battery?

The most common voltages for the PLC batteries are 3 VDC and 3.6 VDC variants.

Normally Lithium or Lithium-ion batteries are used in the PLC system.