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2.1.1 Backup Batteries for the Absolute Specification
The absolute-specification controller uses secondary batteries (nickel metal hydride cells) to retain
absolute counter data in the FPGA (field-programmable gate array) after the power is cut off, and also to
supply power to the encoder’s drive circuit intermittently.
(1) Battery specification
Item Description
Classification Cylindrical sealed nickel metal hydride cell
Manufacturer Matsushita Battery Industrial
Model AB-4
Nominal voltage 4.8 V (1.2 V x 4)
Rated capacity 1900 mAh (average capacity: 2050 mAh)
Average life Approx. 4 years
Charging time
Approx. 48 hours (at ambient temperature of 20°C)
Retention time after power cutoff
Approx. 250 hours (when the batteries are fully charged, at
ambient temperature of 20°C)
(2) Charging the batteries
Be sure to charge the batteries when the controller is powered up for the first time after delivery, and also
after new batteries have been installed.
The batteries are charged automatically while the power is being supplied to the controller, so keep the
main power on for at least 48 hours.
The actuator can be moved and the position table changed while the batteries are charging.
Additionally, charge the batteries for at least 48 hours after the power supply to the controller has been cut
off for a prolonged period (within the specified battery-retention time).
(3) Replacing the batteries
Batteries are consumable parts. Repeated charging and discharging of the batteries will diminish their
initial performance characteristics. If the retention time has decreased significantly, the batteries may have
reached the end of their useful life. If this should occur, replace the batteries.
The batteries should be replaced approximately four years after the controller is first connected to your
equipment, although the specific timing will vary depending on the ambient temperature and conditions of
charge/discharge.
The label on the battery unit shows a reference date, which is four years from the shipment date. Use this
date to determine when the batteries should be replaced.
Note: (1) Applying vibration, impact or other external force to the actuator or moving the slider, etc.,
while the power is off will erase the absolute data.
When the power is input again, the *ALM signal will turn OFF, the ALM lamp will illuminate
and the message “Absolute encoder error (2)” or “Absolute encoder error (3)” will be
displayed.
In this case, you must reset the alarm and perform a home return.
Never move the slider or rod while the power is off!
(2) It is recommended that the batteries be charged at normal temperature (+10 to +30°C) to
prevent extreme temperatures from negatively affecting the charging efficiency.
Temperatures exceeding 45°C may cause performance deterioration or the leakage of
battery fluid.
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