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Correct procedure for replacing battery on older S7-300 (CPU 315-2 DP)

Created by: Pandiani at: 2/19/2007 9:51 AM (6 Replies)

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2/19/2007 9:51 AM	Rate (0)
Pandiani Bronze Member Joined: 10/31/2005 Last visit: 9/4/2024 Posts: 366 Rating: (31)	Hello guys, please can someone explain me a correct procedure for replacing battery in S7300-CPU 315-2 DP? PLC use memory (flash) card (I think it is 256 KB, MC). When I read diagnostic buffer I can see messages about battery. It seems that CPU has some OB that prevents CPU to go into STOP mode. This PLC must not be switched to STOP. So is it possible to replace PLC battery withoutstopping the PLC? Please can you give me step by step algorithm what must I do? Thank you very much.

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2/20/2007 10:05 AM	Rate (1)
Smurf Silver Member Joined: 9/28/2005 Last visit: 10/24/2024 Posts: 414 Rating: (28)	Hi Pandiani, It's quiet simple. Do not switch off the CPU, pull out the battery and replace it for a new one. You do not have to place the CPU in STOP, it is possible to do it in RUN. See also the manuals for the old CPUs.
	Smurf "The only difference between a problem and a solution is that people understand the solution."
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2/21/2007 6:14 PM	Rate (0)
Pandiani Bronze Member Joined: 10/31/2005 Last visit: 9/4/2024 Posts: 366 Rating: (31)	Hello Smurf, I didn't know it just that easy. Please can you tell me if there is need for appropriate OB to be downloaded to CPU first to prevent switching in STOP mode, or simply CPU is not going to be stopped when battery is removed. Thanks

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2/21/2007 7:01 PM	Rate (0)
Mojo Bronze Member Joined: 3/27/2006 Last visit: 10/11/2024 Posts: 90 Rating: (13)	OB81 is called when the battery condition changes on the older CPU models. I usedOB81 to generate a "PLC Battery Low" warning so I am positive this works. I do not think the CPU will fault if this OB81 is not present but you could download an empty OB81 just to be sure.
	"I never let a cowboy make the coffee." Yeah, thats what Granny always said to my Grandad. And he'd say: "Never tell a joke that ain't that funny more than once." "And if you wanna hear God laugh, tell Him your plans." Van Zant "Help Somebody"
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2/22/2007 5:39 AM	Rate (0)
Dec Gold Expert Joined: 5/19/2006 Last visit: 2/8/2025 Posts: 549 Rating: (107)	CPU will not fault (STOP) if you don'thave OB81. It will turn BATF led on only. Dec

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2/22/2007 9:10 AM	Rate (0)
Pandiani Bronze Member Joined: 10/31/2005 Last visit: 9/4/2024 Posts: 366 Rating: (31)	Ok, thanks. Can you tell me what are possible consequences if battery is discharged? Maybe, parts of PLc program that are not copied to ROM will be lost!?!

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2/22/2007 9:47 AM	Rate (0)
Smurf Silver Member Joined: 9/28/2005 Last visit: 10/24/2024 Posts: 414 Rating: (28)	Hi, All information not stored on a PROM is lost at a power loss. That means in your case that settings, only stored in RAM, are lost, but the program and perhaps some basic settings stored on the flash are still there and can be used with the next power on. Of course you can do a sort of copy RAM to ROM to save the actual settings in DBs as the new standard settings, but information stored inM-memory is lost, actuallyall retentive data is lost. This means also that as long as you don't switch off you CPU the data will be kept in RAM. The new type CPUs will backup there RAM-data to the MMC, if there is enough space on the MMC, etc., etc.
	Smurf "The only difference between a problem and a solution is that people understand the solution."
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