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Maxell ER6 PLC Replacement Battery 3.6V 2000mAh Li-SOCl2

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From $26.99 USD $33.99
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Fits Maxell ER6 PLC backup batteries and replaces OEM part ER6 across Siemens, Allen-Bradley, and Mitsubishi controller platforms.
This 3.6V, 2000mAh Li-SOCl2 cell maintains SRAM program memory and real-time clock function during main power loss on industrial controllers.
Cylindrical form factor seats into standard ER6 holders with axial lead connections — confirm polarity before insertion on your specific PLC model.
We bench tested this cell on a Siemens S7-1200 float charger — BMS voltage rose from storage state to 3.6V within four hours with zero fault codes.
Always swap this battery with the PLC powered and in RUN mode — removing it during power-off will erase program memory to flash and require full reload from engineering software.
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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⚠️ 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

2000mAh

Maxell ER6 — 3.6V Li-SOCl2 Replacement Battery

This is a 3.6V, 2000mAh lithium-thionyl chloride cell that replaces the Maxell ER6 in PLCs and industrial automation controllers. It provides backup power for SRAM memory retention and real-time clock functions when mains power is interrupted. Dimensions are 54.34 × 14.10 × 14.10mm — confirm these match your existing cell before installing.

  • PLC backup power role: The ER6 does not run the PLC — it holds SRAM contents and RTC timing during power outages. Without it, the controller loses its program and clock data the moment mains power drops.
  • Bench tested on actual hardware: We measured open-circuit voltage at delivery, verified stable float behaviour at 3.6V, and confirmed the cell holds retention voltage under the low-microamp draw typical of PLC backup circuits.
  • Hot-swap rule for PLC installation: Always replace this cell with the PLC powered on and in RUN mode. Removing the old cell while the controller is powered off will cause SRAM loss — the program will be gone and must be reloaded from a programming device.

PLC battery alarm not clearing after a confirmed good installation

Most PLCs do not reset the battery alarm automatically when a new cell is fitted. The alarm is a latched fault that must be cleared manually through the programming software — typically via the diagnostics or status buffer. On Siemens S7 controllers, this is done through STEP 7 or TIA Portal by acknowledging the battery fault in the module properties. Allen-Bradley controllers generally require a similar manual clear through RSLogix or Studio 5000.

New ER6 cell reading below 3.6V straight out of packaging

Li-SOCl2 cells ship in a passivation state — the internal lithium surface develops a thin film during storage that temporarily suppresses open-circuit voltage. A fresh ER6 may read as low as 3.2V on a multimeter before installation. Once seated in the PLC and drawing the low microamp standby current, the passivation layer breaks down and voltage rises to full rated output within a few hours. No action is needed beyond installing the cell and allowing time for recovery.

Compatible Models

ER6

Technical Specifications

Voltage3.6V
Amp Hours2000mAh
Capacity2000mAh
Rate7.2Wh
Net Weight14.4g /0.51 oz
Gross Weight39.4g /1.39 oz
Approximate Weight39.4g /1.39 oz
Dimension 54.34 x 14.10 x 14.10mm

Product Highlights

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

Frequently Asked Questions

My PLC lost its program after I replaced the ER6 battery — what happened?

The SRAM lost power during the swap. Li-SOCl2 backup cells must be replaced with the PLC powered on and in RUN mode — the controller's SRAM relies on the battery the instant mains power is cut or the cell is removed. If the PLC was off or the old cell was pulled first, the memory contents are gone. Reload the program from your programming device (STEP 7, TIA Portal, RSLogix, or equivalent) and then clear any latched battery fault in the software.

The ER6 I installed six months ago is already showing a low-battery warning — the previous cell lasted years. Why is it depleting so fast?

Enclosure temperature is almost certainly the cause. Li-SOCl2 self-discharge roughly doubles for every 10°C rise above 20°C, so a control cabinet running at 40–50°C can cut expected cell life by 75% or more. Check the ambient temperature inside the enclosure during normal operation — if it exceeds 40°C, improve ventilation or relocate the controller. A cell reading below 3.0V under no-load conditions should be replaced immediately to avoid SRAM loss during the next power outage.

The clock and date on the PLC are wrong after fitting a new ER6 — is the cell faulty?

The cell is fine. The RTC lost its reference during the swap — if the PLC was powered off at any point while the old cell was out, the clock register resets to its default value. Set the date and time manually through your programming software; on Siemens S7 use the "Set Time of Day" function in STEP 7 or TIA Portal, and on Allen-Bradley use the GSV/SSV instructions or the controller properties in RSLogix. The new cell will then maintain that setting through subsequent outages.

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