Hello Neogazz;

The Simatic S7-400 hardware and installation manual suggests that the backup batteries for a S7-400 be replaced every year. See the attached screenshot below.

https://support.industry.siemens.com/cs/ca/en/view/1117849

If you already have a replacement battery on your shelf, check the procedure to remove the passivation layer that forms on a lithuum battery over time before you set it in your power supply, in the same manual.

To purchase a replacement battery, you should look at Tadirn Batteires, model SL 360. The link to find Tadiran is in the document:

https://support.industry.siemens.com/cs/ca/en/view/12067424

.Hope this helps,

Daniel Chartiert

Hi,

for this topic exists another FAQ - it shows you in an example the backup time...and it contains a calculator for backup time.

How great is the power requirement (from the backup battery) of the modules to be backed up at "Power Off" and what is the relationship between the backup current and the length of the backup time?

Regards,

Towome