Ultrasonic Induced Voltage into a Micrologix 1400 PLC?

Hi guys, I'm chasing a strange one here and am trying to eliminate a far fetch theory I have.

Background. I have a machine with 5 Micrologix 1400s whose batteries die prematurely, in the range of 6 months to a year. They are powered up 24/7.
All the typical power and grounds have been checked and we finally replaced all 5 Micrologix 1400 PLCs. 6 months later one of them has a battery fault. There are numerous other Micrologix PLCs in the plant and none of them have every had this issue. There is a machine less than 5' from this one powered off of the same subpanel that doesn't show this issue.

Now for the far fetched theory. The machine uses ultrasonics to clean wire. The wire is ran through the ultrasonic cleaner as a single strand with payoffs and takeups unspooling and respooling. I found some references to some ultrasonics being able to damage electronics such as the following wikipedia link saying "Piezoelectric buzzers can work in reverse and produce voltage, which may pose a danger to their drive circuits."
https://en.wikipedia.org/wiki/Ultrasonic_cleaning

Could the ultrasonics be inducing some type of voltages into the frame of the machine? Anyone ever seen anything like this or a particular setup draining the batteries on a Micrologix 1400 PLC?

Thanks
TW

Had a similar problem on some Siemens stuff many years ago, this turned out to be component tolerances or faulty batches of components in the manufacture, apparently when I spoke to Siemens they had not heard of any problems until some months later they sent an e-mail regarding component issues in particular batches of cards.
On another note: although you say that they are never powered down, my experience of equipment from the states is that many remove the power from the PLC on an e-stop or guard open rather than just removing the power from the outputs although the power is still on the panel.
This caused many failures on some of our machines like low batteries before expected, HMI's (panelviews) and AB inverters dying on a regular basis.
I modified the offending machines so that all PLC & HMI's stayed powered & removed power only from outputs. This cured all the problems and to cure the Inverter problems I replaced them with Mitsubishi, even though these were powered down often when guards were opened we never had the problem again (so much for powerflex sorry my rant).

How well is the ultrasonic cleaner mechanically isolated from the rest of the machine?

Here's an equally off-the-wall explanation. There is (or ought to be) a diode between the battery and the circuit with the RAM memory. The battery voltage should be slightly lower than the normal voltage in that circuit so that under normal operation there is no current flow out of the battery. Vibration of the Micrologix causes a brief disconnect between the Micrologix power supply and the circuit that includes the RAM and battery, not enough to generate a fault but enough drop the voltage below that of the battery so that the battery supplies a portion of the current needed to power the circuit.

If you can't do anything about isolating the ultrasonic cleaner from the rest of the machine consider mounting the Micrologix on an isolation pad.

Steve Bailey said:

How well is the ultrasonic cleaner mechanically isolated from the rest of the machine?

Here's an equally off-the-wall explanation. There is (or ought to be) a diode between the battery and the circuit with the RAM memory. The battery voltage should be slightly lower than the normal voltage in that circuit so that under normal operation there is no current flow out of the battery. Vibration of the Micrologix causes a brief disconnect between the Micrologix power supply and the circuit that includes the RAM and battery, not enough to generate a fault but enough drop the voltage below that of the battery so that the battery supplies a portion of the current needed to power the circuit.

Click to expand...

Hi Steve. There is hardly any vibration even if you lean against the cleaner and the payoffs and takeups are separately mounted to the floor. They are electrically bonded together.

A little more of why I keep looking at then Ultrasonic...
The payoff and takeup are physically different control panels. They are powered out of the same subpanel as is many other machines yet only these the payoff and takeup exhibit the same battery issue. The only common points they have is the wire running through the ultrasonic cleaner in between them and an Ethernet cable.

The wire is spooled on plastic spools would would isolated it electrically, but a bunch of wire wrapped around a spool and slid on a steel shaft kind of sounds like a crude transformer. I know I'm reaching here but this one has been stumping me for a few years.