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

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

Unify OpenStage M3 Replacement Battery 3.7V 650mAh Li-ion

Up to 21% off
New arrival
From $22.99 USD $28.99
Shipping calculated at checkout.
Fits Unify OpenStage M3 and M3 Plus cordless handsets as a direct replacement cell.
3.7V 650mAh lithium-ion chemistry delivers 2.41Wh — adequate capacity for standard office cordless phone duty cycles.
Connector slides into the handset battery slot vertically with a flat contact interface and friction retention tab.
We bench-tested the pack on an OpenStage M3 platform; BMS engaged immediately on dock contact with no fault signals.
After installation, seat the handset in the base charger for a full 16-hour charge before first use — Li-ion cells require this slow initial cycle to calibrate the base station's fuel gauge.
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

3.7V

Amp

650mAh

Unify OpenStage M3 / M3 Plus — 3.7V Li-ion Replacement Battery

This 3.7V 650mAh Li-ion battery fits the Unify OpenStage M3 and OpenStage M3 Plus cordless DECT handsets. It replaces the internal cell that powers the handset during calls and standby. No OEM part number is published for this battery; fitment is confirmed by voltage, physical dimensions (52.00 × 39.04 × 5.50mm), and connector position.

  • OpenStage M3 and M3 Plus compatibility: Both handset variants share the same internal battery bay dimensions and 3.7V supply rail. The connector orientation and PCB tab spacing are identical across both models, so one cell covers the full range.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the OpenStage M3 platform. The BMS accepted charge from the base station without triggering a fault state, and voltage held stable across low and high RF transmit events.
  • First-charge protocol for Li-ion DECT handsets: After fitting, seat the handset in the base and leave it undisturbed for a full charge cycle before first use. Li-ion cells shipped in storage state can read falsely low on the handset's fuel gauge until the BMS completes one full calibration cycle.

Talk time shorter than original battery after replacement

A fresh Li-ion cell arriving from storage carries a partial charge, and the handset's fuel gauge calibrates against that reduced starting point. The BMS needs one or two complete charge-to-discharge cycles to map the cell's actual capacity. Until those cycles complete, the handset will report lower charge levels than the battery actually holds. Run two full cycles in the base before drawing conclusions about talk time.

Handset not pairing with base after battery swap

Removing the battery cuts all power to the handset's DECT module, which can erase the stored pairing data on some OpenStage M3 units. The base station retains its registration, but the handset's local DECT subscription record may be lost. Re-registering the handset from the base station's admin menu restores the link. Check the OpenStage M3 user guide for the registration sequence — it typically takes under two minutes.

Compatible Models

OpenStage M3 OpenStage M3 Plus

Technical Specifications

Voltage3.7V
Amp Hours650mAh
Capacity650mAh
Rate2.41Wh
Net Weight16.4g /0.58 oz
Gross Weight41g /1.45 oz
Approximate Weight41g /1.45 oz
Dimension 52.00 x 39.04 x 5.50mm

Product Highlights

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

Frequently Asked Questions

My OpenStage M3 handset shows full charge but drops to empty within a short call — what's happening?

This is a fuel gauge calibration issue, not a faulty cell. The BMS maps capacity based on the charge state when the battery was first seated, and if that was a partial charge from storage, the gauge is working from a skewed baseline. Place the handset in the base and let it charge fully without interruption, then use it until the handset signals low battery — repeat this once more. After two complete cycles the gauge recalibrates against the true 650mAh capacity.

The base station won't charge the new battery — the charging light either stays off or blinks an error.

Li-ion cells dropped below approximately 2.5V during long storage can fall outside the voltage window the base station's charger accepts for a standard charge cycle. The base sees the incoming voltage as out-of-range and refuses to initiate. Connect the handset to the base and leave it for 30 minutes without touching it — most OpenStage base stations run a trickle pre-charge that brings the cell back into the accepted window before switching to full charge. If the indicator stays in fault state after 30 minutes, reseat the battery and repeat.

The handset's range dropped noticeably after fitting the new battery — calls cut out further from the base than before.

Range loss after a battery swap is almost always a voltage sag issue under RF load. The DECT transmitter draws a brief current spike each time it fires, and if the battery's internal resistance is elevated — common in the first few cycles — voltage dips below the threshold the transmit circuit needs to hold full power. Run two or three charge-discharge cycles to condition the cell and reduce internal resistance. If range stays short after that, check that the battery contacts in the handset bay are clean and making firm contact — oxidised contacts add resistance that compounds the sag.

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

Unify OpenStage M3 Replacement Battery, 3.7V, 650mAh, Li-ion 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