1747-BA | SLC 500 Series PLC Battery Module — User Program and Data RAM Retention / Lithium Cell / Chassis Mount

Why Every SLC 500 PLC Needs a Battery

The SLC 500 CPU stores the user programme, data table values, and system parameters in CMOS RAM — which requires continuous low-level supply voltage to retain its contents. The 1747-BA lithium battery provides this standby voltage whenever mains power is off, preserving programme and data through shutdowns, power failures, and controller servicing. Without it, the CPU loses all RAM content on power removal.

Key Product Information

Memory Protection Strategy

Three-layer best practice for SLC 500 memory protection:

1. 1747-BA battery — automatic RAM retention through power interruptions
2. External programme backup — upload to laptop after any programme change
3. EEPROM module (optional) — non-volatile programme storage independent of the battery

Application Scenarios

Weekend maintenance shutdown: Machine is powered off for 60 hours. 1747-BA retains programme and data intact — PLC restarts in the same operational state.

Proactive battery replacement: CPU shows Battery Low status after several years. 1747-BA is changed at the next planned maintenance window, before any risk of memory loss.

FAQ

Q1: How do I know when 1747-BA needs replacing?

The CPU sets Battery Low status bit S:11/7. Wire it to a fault output or SCADA alarm — this gives weeks to months of advance warning before RAM content is at risk.

Q2: Can the battery be replaced while the PLC is powered and running?

Yes. The internal power supply maintains RAM while power is applied — hot replacement causes no programme loss. Replacing with power off requires fast installation or programme reload from backup.

Q3: How long does 1747-BA last in typical service?

Approximately 3–7 years for a 24/7 continuously-run PLC. Machines shut down daily discharge it faster. Also respect the manufacture date: shelf life is typically 3–5 years.

Q4: Can a generic lithium cell substitute for 1747-BA?

No. Generic cells are not plug-compatible with the SLC 500 battery compartment and may differ in voltage or dimensions. Use the 1747-BA specification only.