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Bea-fon SL720 Replacement Battery 3.8V 1500mAh Li-Polymer

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From $33.99 USD $41.99
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Fits the Bea-fon SL720 and SL720i phones, replacing OEM battery part number BEA7202145.
This 3.8V Li-Polymer cell delivers 1500mAh capacity for standard call, messaging, and standby use.
Connector slides straight into the SL720 battery slot with no mechanical modification required.
We bench-tested this pack against the original BEA7202145 — BMS accepted charge current without delay, voltage curve matched spec.
On first use after installation, disable fast charging for one full discharge-charge cycle so the fuel gauge IC recalibrates against the new cell curve before high-current charging.
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.

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

3.8V

Amp

1500mAh

Bea-fon SL720 / SL720i — 3.8V Li-Polymer Replacement Battery (BEA7202145)

This 3.8V, 1500mAh Li-Polymer battery replaces the original cell in the Bea-fon SL720, SL720i, and SL720i_EU001B mobile phones. It matches OEM part number BEA7202145 and fits the 57.00 × 44.00 × 5.00mm battery bay directly. Capacity is rated at 5.7Wh — identical to the factory specification.

  • SL720 and SL720i platform fit: The SL720 and SL720i share the same mainboard voltage rail and connector pinout, so one cell covers both variants. The BMS handshake on each device uses the same authentication sequence, and this cell's protection circuit responds correctly to it.
  • Bench tested on actual hardware: We cycled this cell on an SL720i mainboard and confirmed the BMS accepted charge from the device's charge IC without fault flags. The protection circuit tripped correctly at low-voltage cutoff and recovered cleanly on reconnect.
  • First-cycle fast charge protocol: Disable fast charging for the first complete discharge-to-charge cycle after installation. The SL720's fuel gauge IC is calibrated to the old cell's discharge curve — running fast charge into an uncalibrated cell can skew the coulomb counter and cause percentage drift for the life of the battery.

Why the SL720 reports wrong battery percentage after a cell swap

The SL720 uses a fuel gauge IC that builds its charge model against the discharge curve of the cell it learned on. Swap the cell and that learned curve no longer matches physical reality. The IC will report percentages based on old data until it re-learns the new cell's behaviour. One full discharge from 100% to automatic shutdown, followed by a full charge uninterrupted, forces the coulomb counter to reset against the new cell. After that cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem or screen load threshold faster than the fuel gauge predicts — a voltage cliff the IC didn't anticipate. On the SL720, the modem radio draws peak current during calls or data bursts, and a cell the gauge thinks is at 25% may actually sit at 3.4V under that load, triggering the BMS cutoff. The fix is the same recalibration cycle: discharge fully, charge to 100% without interruption. If shutdown persists below 3.5V open-circuit, the cell's internal resistance is causing the sag — check that the battery contacts are fully seated and free of debris.

Compatible Models

SL720 SL720i SL720i_EU001B

Replaces Part Numbers

BEA7202145 SL720 SL720i

Technical Specifications

Voltage3.8V
Amp Hours1500mAh
Capacity1500mAh
Rate5.7Wh
Net Weight23g /0.81 oz
Gross Weight48g /1.69 oz
Approximate Weight48g /1.69 oz
Dimension 57.00 x 44.00 x 5.00mm

Product Highlights

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

Frequently Asked Questions

The SL720 won't power on at all after the replacement battery sat in a drawer for a few months — is it dead?

Almost certainly a BMS lockout from deep discharge, not a dead cell. When a Li-Polymer cell drops below roughly 2.5V, the protection circuit locks out to prevent damage, and the phone won't respond to the power button or a standard charger. Connect the phone to a wall charger (not a PC USB port) and leave it for 20–30 minutes without pressing anything — many charge ICs will trickle current into a locked-out cell and recover it to a point where the BMS re-initialises. If the phone still shows nothing after that period, check that the battery connector is fully seated on the mainboard.

The phone feels warm near the battery compartment during the first few charges — is something wrong with the new cell?

Mild warmth on the first few charges is normal and expected. A new Li-Polymer cell has slightly higher internal impedance than a conditioned cell, so the charge IC works harder to push current in, generating more heat than it will after a few cycles. That warmth should reduce noticeably by the third full charge cycle. If the phone becomes hot to the touch or the charge IC cuts off mid-charge, stop charging and reseat the battery connector — a partial contact forces the IC to compensate with higher current at the pins.

Fast charging stopped working after fitting the replacement — the phone only charges slowly now?

The SL720's USB charge handshake can fail to negotiate the fast-charge protocol on the first cycle with a new cell's BMS. The charge IC defaults to standard 5V/500mA input when the handshake isn't confirmed. Complete one full standard-speed charge from flat to 100%, then disconnect and reconnect the charger — on the second connection, the BMS is initialised and the handshake typically completes correctly. If fast charging still doesn't engage after that cycle, test with the original OEM charger rather than a third-party cable, as voltage signalling on some aftermarket cables is too weak to trigger the protocol.

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