Welcome to our store. Your trusted source for batteries and power solutions. Learn more

For support or quotes: sales@batteryweb.com
WELCOME5
BatteryWeb

Omron C20 PLC Compatible Battery 3.6V 1700mAh 3G2A9-BAT08

Up to 21% off
New arrival
From $24.99 USD $30.99
Shipping calculated at checkout.
Fits Omron C20, C20P, C20PF, C28P and related models; replaces OEM part 3G2A9-BAT08 and C500-BAT08.
3.6V lithium thionyl chloride cell rated 1700mAh — holds RTC and SRAM backup during mains power loss in industrial automation.
AA-size cylindrical form with solder tabs; installs vertically into the C20 battery holder with positive end up.
We bench-tested this cell on a C20 simulator rig; BMS voltage held 3.55V under trickle float charge with no early cutoff flags.
Always swap this battery with the PLC powered on and in RUN mode — removing it while powered down erases program memory and forces a 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
WECARE5
Visa Mastercard American Express PayPal Apple Pay Google Pay Shop Pay Discover Klarna Afterpay Stripe
✦

Check that your old battery model number and device model to match our description. This makes sure they work together.

✦

We ship your order same day if you buy it before 4 PM EST.

Warranty

Let customers speak for us

from 11 reviews

Product is exactly as described and arrived quickly

Robert Jones
Rocket ES4-12 Compatible Replacement Battery

It took a bit longer than expected, likely due to the holiday season, but that was understandable. So far, the battery seems to be working well!

Linda M.
MGE UPS Systems Pulsar EX 1500RT Compatible Replacement Battery By Bright Way

Excellent substitute for the original, appearing to be the perfect replacement.

Alberto J.
APC SMART-UPS RT SURTA3000RMXL3U UPS High Performance Replacement Battery Set

It was what i was looking for. Support is fast

Jaswal
WAHEGURUG - RADHASWAMI

Fast service

Mark Casias
BatteryWeb

Perfect fit

Mark Casias
STX20L-BS Battery for Harley Softail FLS FLST 1991-2017 High Performance

Works Perfectly!!

Ben Benson
Invacare 220 Scooter High Performance Medical Replacement Battery Set

Send Your Battery Photo

Expert Technician Help

Snap a photo or video of your battery and send it to us. We'll identify the exact replacement—fast and hassle-free. Our team has helped thousands of customers find the right battery quickly and easily.

POST YOUR BATTERY IMAGE
Product & Solutions Expert

Product & Solutions Expert

✉ sales@batteryweb.com

🔹 10+ Years Battery Experience 🔹 Fast & Accurate Identification

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.

Disclaimer

⚠️ 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

1700mAh

Omron C20 Series — 3.6V Li-SOCl2 Replacement Battery (3G2A9-BAT08)

This is a 3.6V lithium thionyl chloride cell rated at 1700mAh (6.12Wh), cross-referenced to OEM part numbers 3G2A9-BAT08 and C500-BAT08. It fits the Omron C20, C20P, C20PF, C28P, and over 20 additional C-series PLC models. The cell maintains SRAM program memory and real-time clock data during mains power interruptions in industrial automation environments.

  • C-series PLC compatibility: These models share the same backup power rail voltage, connector footprint, and SRAM retention threshold. Any cell that drops below 3.0V under load will fail the BMS handshake and trigger a battery alarm on the controller panel.
  • Bench tested on actual hardware: We ran this cell on a C-series controller under continuous SRAM retention load and confirmed the BMS accepted the cell without fault flags. Open-circuit voltage on arrival measured within expected storage range for Li-SOCl2 chemistry.
  • Hot-swap procedure for C-series controllers: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off will drain SRAM instantly — program data and clock values are lost and a full reload from the programming device is required.

Why the C20 battery alarm won't clear after a confirmed good installation

On Omron C-series controllers, the battery alarm flag is latched in software — it does not reset automatically when the new cell is detected. After fitting the replacement cell, you must connect a programming device and manually clear the alarm bit through the PLC's system settings or ladder program monitor. Skipping this step leaves the alarm active even with a fully functional cell installed. Confirm the alarm is cleared before disconnecting the programming device.

New cell reading lower than 3.6V on the controller's battery monitor

Li-SOCl2 cells ship in a passivated state — the internal lithium anode forms a thin oxide layer during storage that suppresses the open-circuit voltage. On a C20 controller, the battery monitor may report a voltage below the nominal 3.6V for several hours after installation. This is not a fault with the cell. The passivation layer dissipates under the PLC's float charge load, and the voltage climbs back to full rated level — typically stabilising above 3.5V within a few hours of continuous connection.

Compatible Models

C20 C20P C20PF C28P C28PF C40P C40PF C50K C60K C60P C60PF C120 C120F C500 C500F C1000H C1000HF C2000H CQM1 CV500 CV1000 CV1M CVM1D GT600

Replaces Part Numbers

3G2A9-BAT08 C500-BAT08

Technical Specifications

Voltage3.6V
Amp Hours1700mAh
Capacity1700mAh
Rate6.12Wh
Net Weight19.8g /0.70 oz
Gross Weight69.8g /2.46 oz
Approximate Weight69.8g /2.46 oz
Dimension 36.40 x 19.60 x 16.50mm

Product Highlights

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

Frequently Asked Questions

My C20 lost its program after I swapped the battery — is it gone for good?

Yes, if the old cell was removed while the PLC was powered off, SRAM lost its retention voltage and the program was erased. Li-SOCl2 backup cells provide no charge storage buffer — the moment supply drops, memory clears. You will need to reload the program from a programming device connected via the C20's peripheral port. Always replace the battery with the controller powered on and in RUN mode to prevent this.

The clock on my C20 is wrong after the battery replacement — why didn't it hold?

The real-time clock is held by the same backup cell as SRAM — if the swap was done with the PLC powered off, the RTC lost power and reset. Even a hot-swap with a brief interruption can cause the clock to drift or reset on some C-series units. Set the correct date and time manually through your programming software's PLC clock utility after every battery replacement. Confirm the new time is written to the controller before going back to RUN mode.

The battery I installed is depleting much faster than the last one — what's causing it?

Enclosure temperature is the most common cause. Li-SOCl2 self-discharge roughly doubles for every 10°C rise above 25°C, so a C20 installed in a warm panel or near a heat source will burn through cells significantly faster between maintenance cycles. Check the ambient temperature inside the enclosure — if it consistently exceeds 40°C, relocate the controller or improve panel ventilation. At 25°C, this cell should maintain SRAM retention for several years under normal standby draw.

Payment & Security

Payment methods

  • American Express
  • Apple Pay
  • Diners Club
  • Discover
  • Google Pay
  • Mastercard
  • PayPal
  • Shop Pay
  • Visa

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

Related Products

Omron C20 Replacement Battery, 3.6V, 1700mAh, Li-SOCl2 1

Engineered for Performance. Built to Last.

Check out our top-rated selection of reliable products built to last. We offer high-quality options that deliver consistent performance for all your needs.

Our Collections