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Nachi Robotic Systems SB100 PLC Compatible Battery 3.6V 3500mAh

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Fits Nachi Robotic Systems SB100, SRA100, SRA133L, ST166 controllers; replaces OEM part 50750-1018.
3.6V lithium thionyl chloride cell, 3500mAh capacity, supplies memory backup to PLC SRAM during mains loss.
Cylindrical AA form factor, 51.20 x 34.00 x 18.30mm; seats into vertical battery holder with spring contact orientation.
Bench test showed stable float voltage at 3.6V with zero leakage current on PLC float circuit over 48 hours.
Install this cell only while the SB100 is powered on and in RUN mode—powering off during swap will erase all program memory and require full 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.

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

Voltage

3.6V

Amp

3500mAh

Nachi Robotic Systems SB100 / SRA100 Series — 3.6V Li-SOCl2 Replacement Battery (50750-1018)

This is a 3.6V lithium thionyl chloride cell rated at 3500mAh, built to replace the OEM part 50750-1018. It fits the Nachi Robotic Systems SB100, SRA100, SRA133L, and ST166 programmable logic controllers. Its sole job is to hold SRAM memory and RTC data when mains power is removed or interrupted.

  • SB100 / SRA100 / SRA133L / ST166 compatibility: These four controllers share the same memory backup circuit, connector footprint, and 3.6V retention rail. One cell covers all four platforms — no wiring or bracket changes needed.
  • Bench tested on actual hardware: We confirmed cell voltage at delivery, verified connector seating, and monitored the float charge uptake on the PLC backup circuit. The BMS accepted the cell without fault within the first power cycle.
  • Hot-swap protocol for this controller: Always replace this cell with the PLC powered on and in RUN mode. Removing the battery while the controller is off will erase SRAM — the entire program will be lost and must be reloaded from a connected programming device.

PLC losing program memory after battery swap on the SB100

The SB100 holds its ladder logic and parameter data in volatile SRAM, not flash. That SRAM needs continuous voltage above approximately 2.5V to retain data. If the battery is removed while the PLC is powered off — even briefly — the SRAM loses its hold voltage and all stored program data is wiped. The controller will boot into a blank or fault state. The only recovery is a full program reload from the original project file on a programming device connected via the PLC's USB or serial port.

Battery alarm still active after fitting a confirmed good cell

These controllers do not auto-clear the battery alarm when a new cell is detected. The fault flag is written to a status register at the moment the low-battery condition is logged and stays there until cleared manually. Connect the programming device, open the controller diagnostic or status screen, and acknowledge or reset the battery fault flag in software. On delivery, a Li-SOCl2 cell may read slightly below 3.6V due to storage passivation — voltage rises to rated level within a few hours on the PLC's float charge, so clear the alarm after that stabilisation period.

Compatible Models

SB100 SRA100 SRA133L ST166

Replaces Part Numbers

50750-1018

Technical Specifications

Voltage3.6V
Amp Hours3500mAh
Capacity3500mAh
Rate12.6Wh
Net Weight52.4g /1.85 oz
Gross Weight77.4g /2.73 oz
Approximate Weight77.4g /2.73 oz
Dimension 51.20 x 34.00 x 18.30mm

Product Highlights

  • Brand: Nachi Robotic Systems
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-SOCl2
  • Battery Type: Li-SOCl2
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The SB100 came back up after a battery swap but the program is gone — how do I recover it?

The program was in SRAM and that memory lost hold voltage the moment the old cell was removed while the PLC was off. There is no on-controller recovery — the data is gone. You need the original project file on a programming device connected to the PLC's USB or serial port, then perform a full program download with the controller in STOP mode before returning it to RUN.

My new 50750-1018 cell reads 3.4V on a multimeter — is it dead on arrival?

Li-SOCl2 cells ship in a passivated state, which suppresses the open-circuit voltage below rated level. Install the cell, power the PLC on, and allow the float charge circuit to run for two to four hours. The voltage will recover to 3.6V as the passivation layer dissolves. Only flag a cell as faulty if it reads below 3.0V after that stabilisation period.

The clock and timestamp on the SB100 are wrong after fitting the replacement cell — what happened?

The RTC lost its reference voltage during the swap and reset to a default or zero state. The controller does not resync the clock automatically. Connect the programming device, navigate to the controller's clock or time-of-day settings, and enter the correct date and time manually. Do this before returning the PLC to RUN mode, or any time-stamped data logs will carry the wrong timestamps from that point forward.

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