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| Place of Origin | USA |
| Brand Name | SIMENS |
| Certification | CE RoHS |
| Model Number | 1747-BA |
The 1747-BA is the lithium battery that retains the user programme in the RAM of Allen-Bradley SLC 500 series processors. When panel power is removed — intentionally during shutdown or unintentionally during a power failure — the processor's RAM loses its supply voltage. Without a battery, the user programme stored in RAM is lost. When power is restored, the processor starts with empty memory and cannot run the machine.
The 1747-BA prevents this scenario. The battery's 3V lithium cell supplies a trickle current to the processor's RAM when the main power supply is absent. This keeps the RAM content intact — the programme, data table values, and processor configuration remain undisturbed through the power interruption. When power is restored, the processor resumes exactly where it left off.
The FDK CR14250SE cell is a half-AA lithium primary cell — 14mm diameter, 25mm long. This cell chemistry provides the long shelf life, high energy density, and stable voltage under low self-discharge conditions that make it suitable for standby backup applications. The 0.23 grams of lithium content places each 1747-BA battery below the 1-gram threshold that triggers certain air shipping restrictions — up to two batteries can be shipped together under US domestic regulations without the highest hazmat surcharge tier.
The wire leads terminate in a connector that matches the socket on the SLC 500 processor's battery connection port. Replacement is a tool-free operation — unplug the old battery, plug in the new one.
| Parameter | Value |
|---|---|
| Part Number | 1747-BA |
| Voltage | 3.0V |
| Capacity | 850mAh |
| Cell | FDK CR14250SE |
| Size | 0.58" dia × 1.04" long |
| Terminals | Wire leads + connector |
| Lithium Content | 0.23g |
| Shelf Life | 10 years |
| Operating Temp | −60 to +85°C |
| Compatible | SLC 5/01–5/05, MicroLogix 1500 |
Battery service life in a PLC depends on both the battery chemistry and how much work the battery does. When the SLC 500 is powered on, the battery is not used — the processor draws its RAM supply directly from the main supply, not the battery. The battery only supplies current when the PLC is powered off.
Typical battery life guidance for the 1747-BA in Allen-Bradley applications:
These figures assume the PLC is powered on for a significant proportion of time. A PLC that is off more than it is on will drain the battery faster. When the battery voltage falls below threshold, the processor's battery LED or fault indicator activates, alerting maintenance personnel to replace the battery before programme loss occurs.
Q1: Does removing the 1747-BA battery cause the SLC 500 to lose its programme?
If the SLC 500 is powered on when the battery is removed, the RAM retains its programme as long as the main supply is present — the battery is only needed when main power is absent. It is good practice to perform battery replacement with the PLC powered on if possible, minimising the time without backup. If the processor must be powered off, replace the battery quickly. Some processor models allow the programme to be backed up to Flash (EEPROM) memory as an additional retention method.
Q2: What triggers the battery LED warning on the SLC 500?
The SLC 500 processor monitors the battery voltage. When voltage falls below a threshold indicating the battery is near exhaustion, the processor activates its battery low indicator — typically an LED on the processor face or a minor fault code in the processor status. The exact threshold and warning behaviour vary slightly between SLC 5/0x processor models. Address the battery low warning promptly — the battery may have weeks or months of remaining life, or it may be near end of service.
Q3: Is the 1747-BA the same battery used in other Allen-Bradley PLC families?
The 1747-BA is specific to the SLC 500 and MicroLogix 1500 families. Other Allen-Bradley PLC families use different batteries — the MicroLogix 1400 uses the 1769-BA, PLC-5 processors use different battery part numbers, and CompactLogix/ControlLogix systems may use different retention methods. Confirm the exact battery part number from the installed processor's documentation before ordering.
Q4: Why does the 1747-BA require hazardous material shipping treatment?
Lithium primary batteries are classified as hazardous material under IATA, IMDG, and DOT transport regulations because lithium metal is reactive and can ignite if the cell is damaged during transport. The 0.23g lithium content of the 1747-BA is below several regulatory thresholds that trigger the most restrictive shipping requirements, but lithium batteries still require appropriate hazmat labelling, packaging, and carrier notification for air shipments in many jurisdictions.
Q5: What is the storage recommendation for unused 1747-BA batteries?
Store in a cool, dry environment at approximately 20–25°C (68–77°F) with 40–60% relative humidity. Avoid heat, direct sunlight, and high humidity. The 10-year shelf life assumes correct storage conditions. Properly stored batteries retain close to full capacity at installation. Do not store with metal objects that could bridge the terminals.
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