the
large capacity battery of A8BAT-SET for MELSEC-A/QnA series CPU modules.

1. Specifications

Item Specification
Model name A8BAT
Battery type
Lithium/Thionyl chloride primary battery
(assembled battery)
Initial voltage 3.6V
Nominal current capacity 15300mAh (1700mAh 9 pcs)
Storage life 5 years (at normal temperature)
Backup time after power OFF Refer to section 3.1
Application
For memory backup of IC-RAM and retention of
power failure
A8BAT battery
130mm(5.12inch)(H) 34.5mm(1.36inch)(W)
109.6mm(4.31 inch) (D) Dimensions
A8BAT connection cable 800mm(31.5 inch)
Accessory A8BAT connection cable (AC08BAT) 1

2. Applicable CPU modules

Model name Target hardware version
Q2ASHCPU H or later
Q2ASHCPU-S1 H or later
Q4ACPU P or later
Q4ARCPU L or later
A2USHCPU-S1 G or later
A1SHCPU J or later
A1SJHCPU S or later
A1SJHCPU-S8 J or later

3. Battery life and procedure for replacement
3.1 A8BAT battery life
Battery life on each CPU depending on the power-on ratio is shown in the
following table.

Battery life
Actual value
(reference value)*3
CPU
module
type
Power-
on time
ratio
Guaranteed
value*2
Ambient
temperature75

Ambient
temperature
40
Ambient
temperature
25
After SM51, SM52
ON (Backup time
after alarm)*4
0%
8,500hr
1.0 years
27,500hr
3.1 years
32,400hr
3.7 years
90hr
3 days
30%
12,100hr
1.4 years
39,300hr
4.5 years
43,800hr
5.0 years
90hr
3 days
50%
17,000hr
1.9 years
43,800hr
5.0 years
43,800hr
5.0 years
90hr
3 days
70%
28,300hr
3.2 years
43,800hr
5.0 years
43,800hr
5.0 years
90hr
3 days
Q2ASH
CPU
100%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
90hr
3 days
0%
6,900hr
0.8 years
27,500hr
3.1 years
32,400hr
3.7 years
70hr
2 days
30%
9,900hr
1.1 years
39,300hr
4.5 years
43,800hr
5.0 years
70hr
2 days
50%
13,900hr
1.6 years
43,800hr
5.0 years
43,800hr
5.0 years
70hr
2 days
70%
23,200hr
2.6 years
43,800hr
5.0 years
43,800hr
5.0 years
70hr
2 days
Q2ASH
CPU-S1
100%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
70hr
2 days
0%
14,100hr
1.6 years
27,300hr
3.1 years
32,400hr
3.7 years
170hr
7 days
30%
20,200hr
2.3 years
39,100hr
4.5 years
43,800hr
5.0 years
170hr
7 days
50%
28,300hr
3.2 years
43,800hr
5.0 years
43,800hr
5.0 years
170hr
7 days
70%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
170hr
7 days
Q4A
CPU
100%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
170hr
7 days
0%
10,900hr
1.2 years
27,300hr
3.1 years
32,400hr
3.7 years
130hr
5 days
30%
15,600hr
1.8 years
39,100hr
4.5 years
43,800hr
5.0 years
130hr
5 days
50%
21,800hr
2.5 years
43,800hr
5.0 years
43,800hr
5.0 years
130hr
5 days
70%
36,400hr
4.2 years
43,800hr
5.0 years
43,800hr
5.0 years
130hr
5 days
Q4AR
CPU
100%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
130hr
5 days
0%
29,100hr
3.3 years
43,800hr
5.0 years
43,800hr
5.0 years
670hr
27 days
30%
41,600hr
4.7 years
43,800hr
5.0 years
43,800hr
5.0 years
670hr
27 days
50%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
670hr
27 days
70%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
670hr
27 days
A2USH
CPU-S1
100%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
670hr
27 days
0%
32,400hr
3.7 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
30%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
50%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
70%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
A1SHCPU
100%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days


Battery life
Actual value
(reference value)*3
CPU
module
type
Power-
on time
ratio
Guaranteed
value*2
Ambient
temperature75

Ambient
temperature
40
Ambient
temperature
25
After SM51, SM52
ON (Backup time
after alarm)*4
0%
32,400hr
3.7 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
30%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
50%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
70%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days
A1SJH
CPU(-S8)
100%
43,800hr
5.0 years
43,800hr
5.0 years
43,800hr
5.0 years
400hr
16 days

*1: The power-on time ratio indicates the ratio of PLC power-on time to one
day (24 hours). (When the total power-on time is 12 hours and the total
power-off time is 12 hours, the power-on time ratio is 50%.)
*2: The guaranteed battery service life; equivalent to the total power failure
time that is calculated based on the characteristics value of the memory
(SRAM) supplied by the manufacturer and under the storage ambient
temperature range of -25 to 75 (operating ambient temperature of 0 to
55 ).
*3: The actual battery service life; equivalent to the total power failure time
that is calculated based on the measured value and under the storage
ambient temperature of 40 and 25 . This value is intended for
reference only, as it varies with characteristics of the memory.
*4: In the following status, the backup time after power OFF is 3 minutes.
y The battery connector is disconnected.
y The lead wire of the battery is broken.

POINT
(1) Do not use the battery exceeding its guaranteed life.
(2) If it is expected that the battery may be used exceeding its guaranteed life,
take the following measures: operate the system by ROM so that the
program can be protected even if the battery runs out while the PLC is
powered OFF, or back up programs and data in advance after SM52 turns
on (within the backup time for after alarm occurrence).
(3) When the battery (A8BAT) is not connected to the CPU module, its service
life is five years.
(4) When the battery-low special relay SM52 turns on. Immediately change the
battery.
However, if the alarm has not yet occurred, it is recommended to change the
battery periodically according to the operating condition.

3.2 Connecting procedure of A8BAT
Indication for Replacement from A6BAT to A8BAT and A8BAT battery life
ended is as follows. The PLC power needs to be ON for 10 minutes or longer
prior to battery removal.
Make sure to complete the battery replacement within 3 minutes. Failure to do
so may delete the data in memory, although it includes a condenser to back
up the memory for a while without battery. When the MELSEC-A/QnA series
is used as a UL-certificated product, the A8BAT replacement must be done by
service personnel. The service personnel are defined as experienced
technicians who have been sufficiently educated and trained, and are capable
of perceiving and avoiding operational hazard.

2)
Backup the program and the data.
Confirm the
type of the old battery.
Remove the battery connector of
the CPU module, and pull out
A6BAT being used.
Replacing battery.
Turn off the PLC power supply.
Remove the CPU module from the
base unit.
Disconnect the A8BAT connection
cable from A8BAT.
Remove A8BAT from the control
panel.
Mount a new A8BAT onto the
control panel (Screw or DIN rail is
applicable.)
Connect the A8BAT connection
cable to a new A8BAT.
1)
Open the front door of the CPU
module.
3)
Replacing from
A6BAT to A8BAT
Replacing from
A8BAT to A8BAT
H
A6BAT
MELSEC A2USHCPU-S1
RUN
ERROR
L.CLR
RESET
STOP
RUN
RESET
MITSUBISHI
Connector
of battery
Connector
of CPU
module
A6BAT




Fix the A8BAT onto the control
panel.
(Screws or DIN rail is applicable.)
Connect the A8BAT connection
cable to A8BAT while confirming
the direction of each connector.
Fix the A8BAT connection cable
to the control panel.
Turn on the PLC power supply.
2)
Monitor SM51
to verify ON/OFF.
1)
Monitor SM52
to check if bit 0 is ON.
Failure of CPU module battery. Completed
ON
OFF
Bit 0 is OFF
3)
Bit 0 is ON
A8BAT
Control panel
A8BAT
connection cable
R (bending radius)

20mm (0.79 inch)
or more
A8BAT

Mount the CPU module onto the
main base unit so that the A8BAT
connection cable connected to the
CPU module will not interfere with
the other devices.

Wire the connection cable so that
the disconnection protection is
placed inside the case