10MAINTENANCE AND INSPECTION

10.3 Battery Replacement

MELSEC-Q

When the voltage of the program and power interrupt hold-on function backup battery is lowered, the special relays SM51 and SM52 are energized.

Even if these special relays are energized, the contents of the program and power interrupt hold-on function are not erased immediately.

If the energization of these relays is recognized, however, these contents may be deleted unintentionally.

While a total of the power interrupt hold-on time after the SM51 is energized is within a specified time, replace the battery with a new one.

POINTS

The SM51 is used to give an alarm when the capacity of the battery is lowered. Even after it is energized, the data is held for a specified time.

For safety, however, replace the battery with a new one as early as possible. The SM52 is energized when the battery causes a complete discharge error. Immediately after the relay has been energized, replace the battery with a new one.

Whichever voltage of the battery of the CPU module and SRAM card is lowered, the SM51 and SM52 are energized.

To identify the specific battery of the memory of which voltage is lowered, check the contents of the special resisters SD51 and SD52.

When the voltage of the battery of each memory is lowered, the bit corresponding to each of SD51 and SD52 memories is turned on.

Bit No. of SD51 and SD52

Object

Bit 0

CPU module

Bit 1, 2

SRAM card

POINTS

The relation between the backups of the memories preformed by the batteries which are installed on the CPU module and SRAM card is described below. The items that must be considered are the following two points.

1)The battery installed on the CPU module cannot backup the memory of the SRAM card.

2)The battery installed on the SRAM card cannot backup the memory of the CPU module.

Power supply

Battery of CPU

Battery of

Memory of CPU

Memory of

 

Module

Module

SRAM Card

Module

SRAM Card

 

 

Connection

ON

 

 

 

ON

OFF

 

 

 

 

 

 

 

Unconnection

ON

 

 

 

 

 

 

 

 

OFF

 

 

 

 

 

 

 

 

 

Connection

ON

 

 

 

OFF

OFF

 

 

 

 

 

 

 

Unconnection

ON

 

 

 

 

 

 

 

 

OFF

 

 

 

 

 

 

 

 

 

 

 

: Backup enable

: Backup unable

The standard service life and replacement procedures of the battery is described on the next page.

10 - 4

10 - 4