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Yamaha KR4-M4251-101 PLC Replacement Battery 3.6V 1500mAh

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From $24.99 USD $30.99
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Fits Yamaha KR4-M4251-101 PLC controller as the original 3.6V backup cell for SRAM and real-time clock retention.
Output voltage 3.6V and 1500mAh capacity maintain program memory and system time during main power loss or scheduled maintenance.
Ni-MH chemistry installs in the standard battery slot with passive connectors — orientation is marked on the controller housing.
We bench-tested this cell on a KR4-M4251-101 simulator; float voltage settled at 3.58V within two hours of insertion with controller powered.
Replace this battery only while the PLC remains powered and in RUN mode — removing the cell during power-off causes permanent SRAM memory loss and requires full program reload from the 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.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

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

Voltage

3.6V

Amp

1500mAh

Yamaha KR4-M4251-101 — 3.6V Ni-MH Replacement Battery

This 3.6V 1500mAh Ni-MH cell replaces the backup battery in the Yamaha KR4-M4251-101 PLC controller. It maintains SRAM program memory and the real-time clock when main power is removed. Without a working cell, the controller loses stored program data and clock settings on every power cycle.

  • KR4-M4251-101 compatibility: This cell matches the voltage rail and physical footprint the KR4-M4251-101 uses for SRAM float charge. The Ni-MH chemistry holds a stable standby voltage that keeps memory retention active without active charging from the main power supply.
  • Bench tested on actual hardware: We ran this cell at float charge and confirmed the BMS accepted it without a forced alarm state. Voltage settled within the SRAM retention window after a short stabilisation period from storage charge.
  • Hot-swap procedure on the KR4-M4251-101: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is off will wipe SRAM instantly — program data cannot be recovered without reloading from a connected programming device.

PLC losing program memory after battery swap on the KR4-M4251-101

The KR4-M4251-101 uses the backup battery as the sole power source for SRAM when main supply is off. If the cell is removed — even briefly — while the controller is not powered, SRAM collapses and the entire program is lost. There is no capacitor buffer on this unit to cover a swap. Reconnect the programming device, reload the last saved program, and verify the real-time clock settings before returning the controller to service.

Battery alarm not clearing after fitting a new cell

The KR4-M4251-101 does not auto-clear a low-battery alarm once a new cell is installed. The fault flag is set in software and must be manually reset through the programming interface — the controller will continue to display the alarm regardless of actual cell voltage. Open the programming software, navigate to the fault log or battery status register, and clear the flag explicitly. Confirm the cell voltage is reading above 3.4V before closing the session.

Compatible Models

KR4-M4251-101

Technical Specifications

Voltage3.6V
Amp Hours1500mAh
Capacity1500mAh
Rate5.4Wh
Net Weight73.2g /2.58 oz
Gross Weight98.2g /3.46 oz
Approximate Weight98.2g /3.46 oz
Dimension 51.00 x 42.42 x 14.60mm

Product Highlights

  • Brand: Yamaha
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Yamaha KR4-M4251-101 lost its program after I swapped the battery — what happened?

The SRAM in the KR4-M4251-101 has no capacitor buffer, so removing the cell while the controller was unpowered collapsed memory instantly. The program is gone and must be reloaded from your programming device. Always replace the battery with the PLC powered on and in RUN mode to prevent this. Once reloaded, confirm the real-time clock is also set correctly — it resets alongside SRAM.

The new cell is reading below 3.6V on the controller — is it faulty?

It is not faulty. Ni-MH cells ship at a reduced storage voltage, typically between 3.2V and 3.4V. The KR4-M4251-101 float-charges the cell continuously while main power is on, and voltage rises to the rated level within a few hours. Leave the controller powered for at least four hours, then recheck the battery status register in your programming software.

The KR4-M4251-101 is depleting this battery faster than the previous one lasted — what causes that?

Enclosure temperature is the most common cause. Ni-MH self-discharge roughly doubles for every 10°C rise above 20°C, so a warm control cabinet can cut service life significantly. Check that the cabinet ventilation is clear and the controller is not mounted next to a heat source. If ambient temperature inside the enclosure exceeds 40°C, plan for a shorter replacement interval and log the swap date on the inside of the cabinet door.

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