FX3U Battery Problem

[abdoon89]

Hello, I need your help as I have a problem with the battery led in my FX3U, I tried to read the battery value via D8005 register and it gave me 8 which indicates 0.8 volt. However, the battery gives 3.2 when measured with the voltmeter! I tried to remove the battery and the program read 0.4 volts indicating that the PLC is seeing the battery.    

[Inntele]

  Hello,  What is a question? What help do you expect to get from the forum's community?

[abdoon89]

I thought someone might have faced the same problem, and he could help. I teared down the plc and checked the circiuts surrounding the battery but I did in vain.  

[kaare_t]

Have you tried actually replacing the battery? I suppose you measured the V when the PLC was powered on, or there might be a capacitor that was not fully discharged when you measured. In addition a battery can show higher V when there's no load connected.. So in any case I would suggest actually replacing the battery before dismantling the whole unit.

[abdoon89]

I did replace the battery twice, but all of them gave the  same!     Edited December 21, 2015 by abdoon89

[kaare_t]

Then I would say a defect main unit. Never seen this before.

[DWIM]

It an old thread, yes, but google finds it anyway.
 

I just want to confirm, that we had this issue also on a FX3U. Customer calls us because of the Battery Low LED. We replace the battery, LED still on.
Then we check the register D8005. It toggles between 0.4V and 0.5V. We measure without the battery attached 0.456v (+-) at the pins of the battery connector.
It is some internal voltage.

It is possible to set the register D8006 to "3" (0.3V) so the batt LED is not triggered. But, then you loose the indicator. Best is, to make a reminder in code.

Maybe, even with a battery the code/parameters are not latched. We could that not test on site.