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Emporia Smart.4 Compatible Battery AK-S3M-BC 3.8V 2500mAh

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From $28.99 USD $35.99
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Fits Emporia Smart.4, Smart.3 Mini, and Smart 4 smartphones; replaces OEM battery AK-S3M-BC.
3.8V, 2500mAh lithium-polymer cell delivers 9.5Wh to restore full calling, messaging, and app runtime.
Connector slides straight into the battery slot with no locking tab; orientation marked on device.
Bench testing showed the BMS accepted charge on first cycle; fuel gauge IC required recalibration.
On first use, run one complete discharge-charge cycle without fast charging to let the fuel gauge recalibrate against the new cell's discharge curve.
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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

2500mAh

Emporia Smart.4 / Smart.3 Mini — 3.8V Li-Polymer Replacement Battery (AK-S3M-BC)

This is a 3.8V, 2500mAh Li-Polymer replacement battery for the Emporia Smart.4 and Smart.3 Mini smartphones. OEM part number AK-S3M-BC. It fits both the Smart.4 and Smart 3 Mini variants that share the same battery bay and connector pinout.

  • Smart.4 and Smart.3 Mini compatibility: Both models use the same 3.8V battery rail, identical connector orientation, and the same BMS handshake profile — so one cell covers both platforms without any hardware modification.
  • Bench tested on actual hardware: We ran charge cycles on this cell and confirmed the BMS accepts the charge IC handshake cleanly, holds voltage under screen and modem load, and does not trigger the low-voltage protection cutoff during normal discharge.
  • First-cycle calibration on the Smart.4: On first use after installation, disable fast charging and run one full discharge down to automatic shutdown, then charge to 100% uninterrupted. This lets the fuel gauge IC map its coulomb counter to the new cell's discharge curve before any high-current sessions.

Sudden shutdown at 20–30% on the Emporia Smart.4 after a cell swap

This is a voltage cliff issue, not a capacity problem. Under peak modem or display load, a new cell whose fuel gauge IC hasn't been calibrated can hit an internal voltage drop that triggers the BMS low-voltage cutoff — even when the OS reports 20–30% remaining. The phone shuts down because the BMS sees a cell voltage below its safety threshold, typically around 3.2V under load, while the uncalibrated coulomb counter still shows a false-high state of charge. One full discharge-charge cycle after installation recalibrates the curve and eliminates the premature cutoff.

Emporia Smart.4 not powering on after sitting in storage

Li-Polymer cells self-discharge in storage, and if the battery drops below roughly 2.5V per cell, the BMS enters lockout mode to prevent damage — the phone will not respond to the power button at all. Connect the phone to a wall charger (not a USB port) and leave it for 15–20 minutes without pressing anything. The charge IC trickle-charges the cell back above the BMS recovery threshold, typically 2.9V, at which point the BMS unlocks and normal charging resumes. If the charging LED does not appear within 30 minutes, check the cable and adapter output — the recovery current must come from a source delivering at least 5V/1A.

Compatible Models

Smart.4 Smart.3 Mini Smart 4 Smart 3 Mini

Replaces Part Numbers

AK-S3M-BC

Technical Specifications

Voltage3.8V
Amp Hours2500mAh
Capacity2500mAh
Rate9.5Wh
Net Weight39g /1.38 oz
Gross Weight64g /2.26 oz
Approximate Weight64g /2.26 oz
Dimension 72.00 x 52.20 x 5.30mm

Product Highlights

  • Brand: Emporia
  • 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 Emporia Smart.4 shows 25% battery then cuts off completely — is that the new cell or the phone?

That's a fuel gauge IC calibration mismatch, not a faulty cell. The phone's coulomb counter is still mapped to the old cell's discharge curve, so it misreads the new cell's voltage drop under modem or screen load and the BMS cuts power before the real charge is exhausted. Run one full uninterrupted discharge to automatic shutdown, then charge to 100% without interruption. After that cycle the percentage readings track accurately and the early shutdowns stop.

Fast charging stopped working after fitting the replacement battery in the Smart.4 — was it working before?

Fast charge protocols often don't negotiate correctly on the first cycle with a new cell because the BMS hasn't completed its initial calibration handshake with the charge IC. The phone defaults to standard 5V charging as a safety fallback. Run one full standard charge cycle to 100%, then restart the phone and reconnect the charger — the fast charge negotiation typically re-establishes on the second cycle once the BMS registers the cell as conditioned.

The Emporia Smart.4 battery percentage jumps around erratically — 60% one minute, 45% the next — after I put in this battery.

Erratic percentage readings after a cell swap are caused by the fuel gauge IC recalibrating its internal model against the new cell's impedance and discharge curve. The IC hasn't accumulated enough cycle data to produce a stable state-of-charge estimate. This settles after two to three full discharge-charge cycles. Do not interrupt those cycles mid-charge — partial cycles extend the recalibration period and the jumping continues longer.

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