307

Verify alarm and axis number. Navigate to ALARM screen to confirm '307 APC ALARM: n AXIS BATTERY DOWN 1' and note which axis (n) is affected. Check alarm history for frequency and duration of occurrence.

Check battery voltage on DIAGNOSIS screen. Navigate to SYSTEM > DIAGNOSIS and check diagnostic numbers 300-307 (axis dependent, typically D300+axis number for battery voltage) to confirm actual battery voltage reading is between 3.0-3.2V. Normal voltage should be 3.6V or higher.

Verify amplifier LED status. Check the servo amplifier LED for the affected axis. A steady or flashing BATT LED (if equipped on amplifier model) confirms low battery condition. Refer to amplifier model-specific LED diagnostics (αi series shows battery status on 7-segment display).

Replace APC battery assembly. Power down machine and replace the battery pack on the motor encoder (typically connector-mounted battery holder with A98L-0031-00xx part number). After replacement, perform absolute position reset via PMC ladder or Parameter 1815 (APZ) method, then execute reference position return to re-establish home position. Clear alarm with RESET key.

Battery replacement must occur within 2-4 weeks. Do NOT power off the machine unnecessarily before replacement, as this accelerates position data loss risk. Maintain axis power during battery swap if using hot-swap capable systems.

Inspect encoder battery connector. With machine powered down, inspect the battery connector on the encoder (typically 2-pin connector on motor rear). Look for corrosion, bent pins, coolant contamination, or loose connector body. Clean with contact cleaner if contamination is present.

Ensure proper lockout/tagout procedures before accessing motor and encoder assemblies.

Measure battery voltage directly. Using a digital multimeter, measure voltage across battery terminals directly at the battery pack (not at encoder connector). If voltage reads 3.6V or higher at battery but low at encoder, connector or wiring is faulty.

Check encoder cable and battery wiring. Inspect the encoder cable (feedback cable) for damage, especially near cable tracks or at connectors. Check battery wire routing from battery holder to encoder for breaks or pinch points. Replace encoder cable if damaged (verify cable part number from motor nameplate).

Re-seat or replace connector. Clean and re-seat the battery connector firmly. If corrosion or damage is evident, replace the battery holder assembly or encoder connector assembly. After reconnection, monitor diagnostic voltage reading on DIAGNOSIS screen D300-307 to confirm stable voltage reading above 3.4V.

Check for additional encoder alarms. Navigate to ALARM screen and alarm history to check for related alarms such as 400-series (serial encoder alarms), 410 (pulse coder alarm), or 401 (encoder communication error). Presence of multiple alarms suggests encoder or amplifier failure rather than simple battery depletion.

Verify encoder communication on DIAGNOSIS screen. Navigate to SYSTEM > DIAGNOSIS and check encoder feedback diagnostics (D740-D744 for position data, D400-D420 for serial encoder status depending on control series). Erratic position readings or communication errors indicate encoder fault.

Swap battery with known good unit for testing. Temporarily install a new or known-good battery pack and monitor for 24-48 hours. If alarm persists with confirmed good battery and connections, encoder internal battery monitoring circuit or amplifier input circuit is likely defective.