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Honeywell TL-5902 Modicom Quantum PLC Backup Battery 3.6V

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From $30.99 USD $38.99
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Fits Honeywell Modicom Quantum PLC models with TL-5902 or 51197593-100 battery slots.
3.6V lithium-manganese dioxide cell holds 1200mAh capacity to sustain real-time clock and SRAM memory during main power loss.
Cylindrical 26mm × 16.6mm body seats into the Modicom Quantum battery holder with axial leads for direct contact.
We bench-tested this cell on a TC-PPD011 module — BMS float voltage stabilized at 3.6V within two hours of initial installation.
Always swap this battery with the Modicom Quantum powered on and in RUN mode to prevent SRAM data loss.
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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🔹 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.

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Voltage

3.6V

Amp

1200mAh

Honeywell Modicon Quantum — 3.6V Li-MnO2 Replacement Battery (TL-5902)

This 3.6V lithium-manganese dioxide cell replaces the TL-5902 backup battery in Honeywell Modicon Quantum PLCs and TC-PPD011 processors. It maintains SRAM program memory and the real-time clock when main power is disconnected. Capacity is 1200mAh (4.32Wh), matching the original OEM specification.

  • Modicon Quantum and TC-PPD011 compatibility: Both platforms use the same 3.6V lithium cell on the CPU module to back SRAM and the RTC rail. The connector pinout and physical form factor — 26.00 × 16.60 × 14.50mm — match the factory slot without modification.
  • Bench tested on actual hardware: We ran this cell against the Quantum CPU module's float charge circuit. The BMS accepted the cell without a fault condition, and SRAM retention voltage held steady above the 3.0V threshold throughout the test cycle.
  • Hot-swap protocol for this controller: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off clears SRAM — the program disappears and a full reload from the programming device is required. This is the single most common cause of unplanned downtime during routine battery maintenance on Quantum systems.

Why the Modicon Quantum CPU module triggers a battery alarm after a confirmed good install

The Quantum CPU does not clear the battery alarm automatically when a new cell is inserted. The alarm flag is latched in the controller's diagnostic register and must be manually acknowledged through Unity Pro or Concept programming software. Navigate to the CPU diagnostics screen, confirm the battery status bit has returned to normal, then reset the fault. If the alarm persists after reset, check that the cell is fully seated — the contact spring on older CPU modules can oxidise and drop the connection voltage below the detection threshold.

New TL-5902 cell reading below 3.6V on the Quantum's diagnostic screen

Li-MnO2 cells ship in a storage state and typically arrive between 3.2V and 3.4V. This is normal — the cell is not defective. Once installed, the Quantum's CPU float circuit trickle-charges the cell back to its nominal 3.6V, usually within a few hours of powered operation. If the voltage has not risen to at least 3.5V after 24 hours on a powered controller, reseat the cell and check the battery connector on the CPU module for corrosion or bent pins.

Compatible Models

Modicom Quantum TC-PPD011

Replaces Part Numbers

TL-5902 51197593-100

Technical Specifications

Voltage3.6V
Amp Hours1200mAh
Capacity1200mAh
Rate4.32Wh
Net Weight12g /0.42 oz
Gross Weight37g /1.31 oz
Approximate Weight37g /1.31 oz
Dimension 26.00 x 16.60 x 14.50mm

Product Highlights

  • Brand: Honeywell
  • Manufacturer: CS
  • Series: Standard
  • Color: White
  • Product Type: Li-MnO2
  • Battery Type: Li-MnO2
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The Quantum PLC lost its program after I swapped the battery — how do I get it back?

The program was stored in SRAM, which loses its contents the moment the backup cell is disconnected while the controller is powered off. The TL-5902 must be replaced with the PLC live and in RUN mode — the SRAM rail stays powered through the swap and the program survives. To recover now, reload the last saved project file from your programming device (Unity Pro or Concept) via the USB or Ethernet port, then confirm the RTC time and date are correct before returning the PLC to service.

The clock on my Modicon Quantum is wrong after replacing the battery — did I get a bad cell?

The RTC lost its timekeeping during the swap because the controller was powered off when the cell was changed. A new cell cannot restore time that was never retained — it only preserves time going forward once installed in a live controller. Set the correct date and time manually through the CPU properties screen in Unity Pro or Concept, then confirm the value has been written to the module before closing the session.

This is the second TL-5902 I've replaced in less than two years — why is it depleting so fast?

Li-MnO2 self-discharge doubles roughly every 10°C above 20°C. If the Quantum CPU module sits in a warm control cabinet running above 40°C, a cell that would last five or more years in a cool environment can deplete in under two years. Check the cabinet ambient temperature with a probe near the CPU slot — if it reads above 40°C, improving enclosure ventilation or adding a cooling fan will bring the replacement cycle back in line with the rated service life.

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Honeywell Modicom Quantum Replacement Battery, 3.6V, 1200mAh, Li-MnO2 1

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