The AC500 Battery

The AC500 battery buffers the following data in case of “control voltage off”:

• Retentive variables in SDRAM (VAR_RETAIN..END_VAR)
• File “Persistent.dat” in SDRAM (VAR_RETAIN PERSISTENT .. END_VAR) (in version V1.0.x only)
• Persistent data in %R area (as of version V1.2.0)
• Date and time of the real-time clock

Note

• For AC500-eCo CPUs PM55x and PM56x, the battery is not required for retentive/persistent variables. These variables are stored in the FLASH memory when the CPU is shutting down.
• For AC500 CPU PM595-M-4ETH, no battery is needed to buffer retentive/persistent variables as the MRAM will keep its content during power-off. Only the real-time clock is buffered by the battery.

If no battery is inserted or if the battery is empty, a warning (E4) is generated and the LED “ERR” lights up.

If no battery is required for the application (and thus no battery is inserted), a warning is generated and the error LED lights up each time the controller is switched on. To avoid this battery error indication, the parameter “Check Battery” is available under “CPU parameters” in the PLC configuration. The default setting of this parameter is “On”, i.e., battery check is performed. If this parameter is set to “Off”, the battery check is still performed and a corresponding error message is still generated each time the control voltage is switched on, but the system automatically quits this error and therefore the error LED does not light up (provided no further error exists).

The status of the battery can be checked in the PLC-Browser using the command “batt”. The following is output:

0	Battery empty
20	Remaining battery charge below 20 %
100	Battery charge OK

In the user program, the battery status can be checked with the function “BATT” which is available in the folder “Battery” of the system library SysExt_AC500_Vxx.lib. The following is output:

0	Battery empty
20	Remaining battery charge below 20 %, battery must be replaced
100	Battery charge OK