This is on an Allen-Bradley MicroLogix 1400.
Has anyone ever seen a case where one of these PLCs, powered up 24/7, drains the backup battery within a matter of a few months at most?
I was surprised originally to find the battery dead several months ago, since the whole unit is only a few years old and typically the batteries last for 10+ years on a system that is constantly powered because the lifetime is essentially the shelf life of the battery and 20 years is not uncommon on these cells. I just chalked it up to being a defective battery that had faulted internally and self-discharged earlier than expected, got another good quality 14250 lithium primary cell and stuck it in, expecting it to work for many, many, many years.
Well, someone threw a breaker the other day trying to reset something and the PLC lost all its programming. I tested the cell. *0* volts across it. Something is obviously killing these backup batteries.
I'm guessing it is a leaky diode in the PLC or something, has anyone ever seen this before on these units? It seems to be a quite strange and rare problem...