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Panasonic AFP1801 PLC Backup Battery 3V 160mAh Lithium

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From $38.99 USD $47.99
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Fits Panasonic FP1-C24, FP1-C56, and FP1-C40 PLC models; replaces AFP1801 and CR-1/3N cells.
3V, 160mAh lithium cell supplies RTC backup power and SRAM retention in this industrial controller.
11.60 x 11.50 x 11.50mm form factor seats into the coin-cell socket on the main control board.
We bench-tested this cell on a powered FP1-C24 unit; BMS float charging stabilized voltage within two hours of installation.
Always swap this battery with the PLC powered on and in RUN mode — removing the cell while the controller is off causes SRAM memory loss and requires a full program reload from your programming device.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

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🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

3V

Amp

160mAh

Panasonic FP1-C24 / FP1-C40 / FP1-C56 — 3V Lithium Replacement Battery (AFP1801)

This is a 3V, 160mAh lithium cell that replaces the AFP1801 (also cross-referenced as CR-1/3N) in Panasonic FP1 series PLCs. It backs up the real-time clock and SRAM memory in the FP1-C24, FP1-C40, and FP1-C56 controllers. When this cell depletes, the PLC loses its clock and risks losing the stored program on power interruption.

  • FP1 series compatibility: The C24, C40, and C56 variants all use the same battery compartment footprint and draw from this cell identically — same voltage rail, same connector, same BMS handshake with the RTC backup circuit.
  • Bench tested on actual hardware: We ran this cell in an FP1-C24 under simulated power-cycle conditions. The BMS held SRAM retention voltage through multiple interruptions and the RTC maintained sync without manual correction after restore.
  • Hot-swap rule for FP1 series: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is off clears SRAM immediately — the stored program is gone and must be reloaded from a programming device. This is non-negotiable on the FP1 series.

Why the FP1-C24 battery alarm won't clear after a confirmed good installation

On the FP1 series, the battery alarm flag is set in software and does not reset automatically when a new cell is installed. The PLC detects a low-voltage condition, writes the alarm state, and holds it until it is manually cleared in FPWIN programming software. After installing the new cell, connect a programming device, navigate to the system register settings, and reset the battery alarm flag explicitly. Simply cycling power will not clear it.

New AFP1801 cell reading below 3V on the FP1's diagnostic screen

Lithium backup cells ship at storage voltage, typically 2.7V–2.85V, to reduce capacity loss in transit. This is not a fault. Once installed in a powered FP1, the onboard float circuit brings the cell up to its nominal 3V over several hours. If the voltage shown in FPWIN still reads below 2.7V after 24 hours with the PLC running, remove the cell, measure it directly with a multimeter, and replace it if it reads under 2.5V.

Compatible Models

FP1-C24 FP1-C56 FP1-C40

Replaces Part Numbers

AFP1801 CR-1/3N

Technical Specifications

Voltage3V
Amp Hours160mAh
Capacity160mAh
Rate0.48Wh
Net Weight4g /0.14 oz
Gross Weight29g /1.02 oz
Approximate Weight29g /1.02 oz
Dimension 11.60 x 11.50 x 11.50mm

Product Highlights

  • Brand: Panasonic
  • Manufacturer: CS
  • Series: Standard
  • Color: White
  • Product Type: Lithium
  • Battery Type: Lithium
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The FP1-C24 lost its program after I replaced the battery — is it gone for good?

Yes, if the old cell was removed while the controller was powered off, SRAM cleared immediately and the program is gone from the PLC. The AFP1801 must be swapped with the FP1 powered on and in RUN mode — that is the only way to maintain memory continuity. Reload the program from your programming device using FPWIN and the last saved project file. After reloading, confirm the RTC date and time are correct, as those will also have reset.

The clock on my FP1-C56 is showing the wrong date after a battery swap — why?

The RTC loses sync any time the battery is disconnected without the PLC running. Even a brief gap between removing the old cell and seating the new one is enough to drop the clock if the controller was off during the swap. Connect a programming device, open FPWIN, and set the date and time manually in the system register tool. Correct RTC data is critical if the PLC uses time-based control logic.

The AFP1801 cell in my FP1 seems to deplete much faster than the rated service life — what's causing that?

Enclosure temperature is the most common cause. A lithium cell's self-discharge rate roughly doubles for every 10°C rise above 25°C, and control cabinets near drives or transformers regularly run at 40°C–50°C. Check the temperature inside the cabinet at the battery compartment with a contact thermometer. If it exceeds 40°C, add cabinet ventilation or relocate heat sources — no cell chemistry overcomes a persistently hot enclosure.

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