Bea-fon SL651a Replacement Battery 3.7V 900mAh
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Bea-fon SL651a Replacement Battery 3.7V 900mAh - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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
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
⚠️ 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.
Bea-fon SL651a Replacement Battery 3.7V 900mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.7V
Amp
900mAh
Bea-fon SL651 — 3.7V Li-Polymer Replacement Battery (SL651a)
This 3.7V, 900mAh Li-Polymer cell replaces the original SL651a battery in the Bea-fon SL651 mobile phone. It restores power to calling, messaging, and standby functions on this device. Dimensions are 51.30 × 42.60 × 4.50mm — confirm physical fit before installation.
- SL651 and SL651a compatibility: Both models use the same OEM part number SL651a, share the same connector pinout, and accept the same BMS handshake at 3.7V nominal. One cell covers both variants.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the SL651 platform. The BMS accepted the cell without fault codes, and charge termination triggered correctly at full capacity.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins on an uncalibrated cell.
Sudden shutdown at 20–30% on the replacement cell
A new Li-Polymer cell has a slightly different voltage-versus-capacity curve than the original. The SL651's fuel gauge IC was calibrated to the old cell, so it misreads the remaining charge under load. When the modem or screen draws peak current, the cell voltage drops below the BMS cutoff threshold before the percentage readout reaches zero. Run two full discharge-to-charge cycles without interruption. After the second cycle, the coulomb counter recalibrates and the shutdowns typically stop.
OS reporting wrong battery percentage after a cell swap
The SL651 uses a fuel gauge IC that tracks charge by counting coulombs against a stored cell profile. Swapping the cell resets the physical reference but not the stored profile, so the percentage display drifts — often reading 100% when the cell is partially charged, or dropping suddenly. Let the phone discharge fully until it powers off, then charge uninterrupted to 100%. One full cycle is usually enough to anchor the gauge to the new cell's actual capacity at 3.7V nominal.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Bea-fon
- Manufacturer: CS
- Series: Standard
- Color: Black
- Product Type: Li-Polymer
- Battery Type: Li-Polymer
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
My Bea-fon SL651 powers off suddenly at around 25% after I fitted the new battery — is the cell faulty?
Almost certainly not faulty. The fuel gauge IC on the SL651 was calibrated against the discharge curve of the original, worn cell. The new 900mAh Li-Polymer cell has a steeper voltage drop near the low end, and the modem's transmit current pulls the voltage below the BMS cutoff before the percentage reaches zero. Run two uninterrupted discharge-to-charge cycles — no top-up charges in between. After that the coulomb counter anchors to the new curve and the early shutdowns stop.
The phone won't turn on at all after the replacement battery sat in a drawer for a few months before installation — how do I recover it?
Li-Polymer cells self-discharge in storage, and if the voltage dropped below roughly 2.5V the BMS has tripped into lockout to prevent cell damage. Connect the phone to a wall charger — not a USB port — and leave it for at least 30 minutes before pressing the power button. The charge IC trickle-charges the cell at low current until it clears the BMS recovery threshold, typically around 2.9V per cell, at which point normal charging resumes.
The battery percentage on my SL651 jumps around erratically — it reads 60%, then 80%, then drops to 40% within minutes. What's happening?
This is the fuel gauge IC recalibrating after a cell swap. The stored charge model no longer matches the new cell's impedance and capacity, so percentage readings are inconsistent until the IC gathers enough cycle data to rebuild the profile. Discharge the phone fully until it powers off on its own, then charge it to 100% without interruption. After one complete cycle the readings stabilise; a second cycle locks them in reliably.
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