Siemens S7-400 CPU uses lithium battery (lithium / thionyl chloride). The passive film will be formed when the lithium battery is placed for a long time, which will directly affect the function of the backup battery. In this case, when the system power is on, the CPU will prompt an error message. The backup battery will be de passivated when the power supply module is powered on. Put the lithium battery into the power supply unit of S7-400 to remove the passivation film of the lithium battery. This process takes a few minutes. When the passive film is removed and the lithium battery reaches its rated voltage, the FMR button can be used to confirm the error message of the power module.

Since the storage time of lithium batteries is usually unpredictable, the following steps are recommended to remove the passive film:

Put spare batteries in the battery compartment.

Use fMR button to confirm all battery fault information of power supply unit.

If the battery failure cannot be confirmed, wait a few minutes and try again.

If it is still unable to confirm the battery failure, pull out the battery (pack) and short circuit them for 1 second to 3 seconds. Note that the short circuit time should not exceed 3 seconds.

Re insert the battery (pack) and try to confirm again with the FMR button.

When the displayed battery fault information disappears, the battery (pack) can be ready for use.

If the displayed battery fault information does not disappear, the battery (pack) is dead.

Editor in charge: LQ

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