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Bea-fon SL660 Replacement Battery 3.7V 900mAh Li-ion

Up to 21% off
New arrival
From $22.99 USD $28.99
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Fits Bea-fon SL660, SL652A, SL652AF, SL670 and replaces OEM battery part numbers SL670, SL630, SL640.
This 3.7V 900mAh Li-ion cell restores full charge cycles to the SL660 after degradation cuts runtime short.
Connector slides straight into the battery slot with no locking tab; polarity marked on the cell and housing.
We bench-tested this cell in an SL660 unit and confirmed the BMS accepted the pack on first insertion without fault codes.
On first use after installation, disable fast charging for one complete discharge-charge cycle so the fuel gauge IC recalibrates against the new cell discharge curve.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
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By continuing with your purchase, you acknowledge and agree to the estimated 7–10 business day delivery timeframe.
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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.

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

900mAh

Bea-fon SL660 Series — 3.7V Li-ion Replacement Battery (SL670, SL630/SL640)

This 3.7V 900mAh Li-ion cell replaces the original battery in the Bea-fon SL660, SL652A, SL652AF, and SL670, along with four additional SL-series variants. It fits the same physical footprint at 46.47 × 39.79 × 5.33mm and connects to the stock charge IC without modification. Capacity is 3.33Wh, matching the original cell specification.

  • SL-series compatibility: The SL652A, SL652AF, SL660, and SL670 share the same battery bay dimensions, connector pinout, and charge IC protocol. One cell revision covers the full range without wiring changes or adapter plates.
  • Bench tested on actual hardware: We cycled the cell through charge and discharge on the SL660 platform. The BMS held charge termination voltage correctly, and the fuel gauge IC accepted the new cell without throwing a fault flag after the first full cycle.
  • Fuel gauge recalibration after swap: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

Why the SL660 reports wrong battery percentage after a cell swap

The SL660 uses a fuel gauge IC that stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The gauge reads voltage and estimates percentage against old data, so the number on screen can be off by 10–20%. One full discharge down to auto-shutdown, followed by a complete charge to 4.2V, resets the coulomb counter and lets the gauge relearn against the new cell.

Sudden shutdown at 20–30% remaining on the SL660

This is a voltage cliff, not a software bug. Under modem or screen load, the cell voltage drops sharply at low state of charge. If the fuel gauge IC is still calibrated to the old cell, it predicts more remaining capacity than actually exists, and the phone hits the BMS undervoltage cutoff without warning. The fix is the same full recalibration cycle — discharge to shutdown, charge uninterrupted to 4.2V, then let the gauge operate normally for two more cycles before trusting the percentage readout.

Compatible Models

SL660 SL652A SL652AF SL670 SL625AD SL630 SL640 SL652AD

Replaces Part Numbers

SL670 SL630/SL640

Technical Specifications

Voltage3.7V
Amp Hours900mAh
Capacity900mAh
Rate3.33Wh
Net Weight20g /0.71 oz
Gross Weight45g /1.59 oz
Approximate Weight45g /1.59 oz
Dimension 46.47 x 39.79 x 5.33mm

Product Highlights

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

Frequently Asked Questions

My Bea-fon SL660 won't turn on at all after sitting in a drawer for months — new battery still dead?

A cell stored discharged below 2.5V triggers BMS lockout as a protection measure. Connect the phone to a charger and leave it for 20–30 minutes without attempting to power it on — the charge IC needs time to trickle current into the locked-out cell before the BMS releases and allows normal operation. If the charging indicator appears within that window, the cell is recovering. If nothing appears after 45 minutes, the cell may have dropped below the BMS recovery threshold and will need to be replaced through the supplier.

The SL660 percentage jumps around erratically — shows 60%, drops to 15%, then jumps back up?

The fuel gauge IC is recalibrating against the new cell's discharge curve and hasn't built a stable model yet. This is normal for the first two to three cycles after a cell swap. Run the phone down to auto-shutdown each time and charge fully to 4.2V without interruption. The erratic jumps narrow significantly after the third complete cycle as the coulomb counter accumulates enough data to estimate capacity accurately.

Fast charging stopped working after I fitted the replacement battery in my SL660 — only slow charges now?

The charge IC on the SL660 runs a handshake at the start of each session. On a new cell with higher internal impedance than a degraded original, the IC can default to a lower current limit on the first cycle as a precaution. Charge the phone fully once on the standard slow rate without interruption. On the next session, fast charging typically resumes once the IC has logged one complete successful charge cycle against the new cell's impedance profile.

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