What causes fault code AB-F004 (PLC Battery Low)?

Battery has reached end of life — typical life is 2-3 years. High ambient temperature accelerated battery drain. Processor has been in storage without power for extended period. Battery connector not fully seated

How do I fix fault code AB-F004?

Replace battery while processor is powered ON to prevent data loss. Use correct battery: 1756-BA1 for ControlLogix, 1769-BA for CompactLogix. After replacement, clear battery low bit in controller properties. Record replacement date on label attached to processor. Verify program auto-save is configured as backup

PLC Battery Low

AB-F004

Processor battery is low or depleted. Program and data retention at risk during power loss.

low allen-bradley

allen-bradley battery plc maintenance

Probable Causes (ranked)

Battery has reached end of life — typical life is 2-3 years
High ambient temperature accelerated battery drain
Processor has been in storage without power for extended period
Battery connector not fully seated

Fix Steps

1 Replace battery while processor is powered ON to prevent data loss
2 Use correct battery: 1756-BA1 for ControlLogix, 1769-BA for CompactLogix
3 After replacement, clear battery low bit in controller properties
4 Record replacement date on label attached to processor
5 Verify program auto-save is configured as backup

Field Trick

ALWAYS replace the battery with the PLC powered up. If you pull the old battery with power off, you may lose the program.

Suggested Replacement Parts

Parts matched to fault category: Plc Battery

Allen-Bradley 1756-BA2 PLC Battery P/N: 1756-BA2 ControlLogix battery module, 3V lithium, 2-year life

AutomationDirect $22.00 Amazon $18.00 Grainger $28.00

Mitsubishi Q6BAT PLC Battery P/N: Q6BAT MELSEC-Q series, 3.6V lithium, ER17330V

Amazon $12.00 Digikey $15.00 AutomationDirect $14.00

Siemens 6ES7971-0BA02 PLC Battery P/N: 6ES7971-0BA02 S7-300/400 backup battery, 3.6V lithium AA

Amazon $15.00 Mouser $18.00

Prices are estimates. Verify part numbers match your equipment before ordering.

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