SM51 and SM52 Q50UDEH Battery removal

[Andrei Blagaila 4]

Hi guys,

I want to create a small pop up message in my HMI and PLC software when the bettery is low to inform the operator that it needs to be changed. For that I plan to use SM51 and SM52 (one turns on when the voltage drops and turns off if it comes back up and the other stays on if the voltage drops one time and the battery is not changed). I have a Q50UDEH CPU in my office and I want to run some tests. I want to remove the battery while the CPU is running and then connect it back again. Can I do this or are there chances for the CPU to break? (i know it's kind of a stupid question because if the battery dies it does the same thing but I just wanna make sure).

Thanks

[JRoss 84]

The battery is designed to be replaced while the PLC is powered up. Also, in the Q-series it is not used for program memory, just for device memory. If you take the battery out and cycle power, you won't lose the program, but all your data registers and memory bits will be reset to zero.

[kaare_t 155]

20 hours ago, JRoss said:

Also, in the Q-series it is not used for program memory, just for device memory

Sorry @JRoss but this is not correct. The Q-series use the battery also for program! You can install a memory card to retain the program, but unless you have that the program is also stored in the battery backed memory. However, there are capacitors in the CPU, so you will have some time after the PLC is powered off to change the battery, but this is not recommended since no-one have a documented time-window while the power is off and the battery is out...

An exception is the Q00/Q01 (and possibly Q00J) CPU's, they have a feature with a built-in flash which you can choose to write to in the software (not enabled by default).

Except from that, you can as @JRoss writes change the battery with the power on.

[Andrei Blagaila 4]

On the CPU there is a sticked that sais to replace the battery within 3 minutes. So in order to change the battery without loosing the program I suspect the only way is to do it while having the power ON. 

Thank you guys :)

[kaare_t 155]

Replace it within 3 minutes when the power is off (but the undocumented version is that you can use more time than that -> note that I won't guarantee anything). But again, as @JRoss writes, do it while the power is on...

[JRoss 84]

Whoops! Guess I'm more used to the FX series.