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Old July 13th, 2010, 02:59 AM   #1
Michael Hunt
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Procedure for changing battery on S7-400 and S7-300

Hi

Would anyone have a procedure for replacing batteries on Siemens S7-300 and S7-400 PLC's.

Thanks
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Old July 13th, 2010, 09:16 AM   #2
dchartier
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Hello Mickey;
There are no batteries in the newer S7-300 CPU modules, so that question is answered easily (they use MMCs for program and data retention nowadays).
Batteries for the S7-400 are inside the power supply module. In case you have an older S7-300 CPU with battery, the procedure is the same as the one for the S7-400: remove the defective battery while power is on (or you might lose your program memory)and insert replacement battery into the free slot(s).
If you have any doubts, look at the section on battery replacement in the S7-400 hardware and Installation manual:
http://support.automation.siemens.co...iew/en/1117849
Hope this helps,
Daniel Chartier
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Old August 9th, 2011, 05:15 PM   #3
Farnesi
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Hi

Sorry for reviving the subject but I thought it would be better than creating other topic. The deal is my S7-400 PS 407 has battery failure and I replaced the battery 5 times already in a row - so I'm 100% sure it's not the battery fault. What could it be? The power supply itself? Is it in danger of failing completely?
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Old August 10th, 2011, 02:03 AM   #4
rohan tandon
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The battery should last for a year atleast, provided you are using the original battery. What was the interval between failures?

If the failure is happening too frequently then you should change the power supply.


i hope you are resetting the fault on the power supply after changing the battery.
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Old August 10th, 2011, 02:08 AM   #5
iant
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where did you get the battery from
SHelf Life is limited
Also CHange over while power is on
it shoul be a lithium Ion 3.6v battery
definately not a std AA 1.5 v

Once you change it you may need to reset the fault
Don't power down under any cirmstances you will loose the program
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Old August 10th, 2011, 11:33 AM   #6
Farnesi
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It is a Saft LS-14500 battery AA 3.6V

SIEMENS told me to check it's current and it is around 0.20mA. According them it should be 1.5A but I doubt it cause i m using the same battery on other S7-400 rack which doesn't point out battery failure.

Yes I reset BAF after replacing.

I'm scheduling a power supply replacement but I'm not 100% sure... Any tips?
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Old August 10th, 2011, 02:21 PM   #7
rohan tandon
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I think changing the power supply is a good idea as the frequent battery failure is unusual.

You will loose the PLC memory on changing the power supply so make sure you upload the program. Incase you have a flash memory card then the program can be reloaded from the flash memory but the memory bit and actual values of the DB will be lost and set to initial values. If you are sure that the program on the flash memory is a working program then you dont have anything to worry about.

After changing power supply, the CPU will go into a fault on first startup requesting memory reset and then take a couple of minutes to go to run as it will do a complete memory test.
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Old August 10th, 2011, 10:24 PM   #8
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This can damage meters so be careful
with a new battery
1. measure the battery voltage
2. set the meter to Current (10A) range
3. place the battery leads on either side of the battery and read the current - the meter could peek high - if so stop test.

do the same with the old battery

I agree with Rohan's comment.
This will confirm the battery condition
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Old August 11th, 2011, 10:15 AM   #9
dchartier
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Quote:
Originally Posted by rohan tandon View Post

You will loose the PLC memory on changing the power supply so make sure you upload the program.
A very good suggestion, it is always preferable to do an upload of the program before attempting any major hardware change on a PLC.
However, there is a way to maintain power to the PLC RAM (we are discussing S7-400 CPUs here), using the EXT. BATT. connector on the front of the CPU module. I used to connect a 9V battery to a simple audio jack and plug it to this EXT. BATT. connector, that would give me a few hours autonomy for the program memory. There is a link to the complete procedure in this FAQ from Siemens, for those who could be interested:
How do you provide an external backup supply for an S7-400 CPU?
Hope this helps,
Daniel Chartier

Last edited by dchartier; August 11th, 2011 at 10:19 AM.
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Old August 15th, 2011, 12:16 PM   #10
Farnesi
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I replaced the power supply and installed a flash memory card... Yes it was the power supply faulting the battery.

Thank you all

Nice to know dchartier about the ext.batt "tweak"... I thought I had to buy the battery but I can build one...
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