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MyPhone MP-S-A2 Replacement Battery 3.7V 900mAh Li-ion

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From $22.99 USD $28.99
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Fits MyPhone MP-S-A2 smartphones; replaces OEM battery part number MP-S-A2.
3.7V, 900mAh lithium-ion cell delivers 3.33Wh to sustain call time and standby on compatible MyPhone devices.
Connector type and orientation match OEM slot; dimensions 53.00 x 34.00 x 4.80mm confirm physical fit without modification.
We cycled this pack on bench; BMS accepted charge current without fault codes and held voltage under moderate discharge load.
On first use after installation, disable fast charging for one complete discharge-charge cycle so the fuel gauge IC recalibrates against the new cell 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

3.7V

Amp

900mAh

MyPhone MP-S-A2 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion cell replacing the OEM MP-S-A2 battery in compatible MyPhone smartphones. It measures 53.00 × 34.00 × 4.80mm and delivers 3.33Wh of capacity. If your phone is shutting down early, failing to charge, or the original cell has swollen, this is the direct swap.

  • MyPhone MP-S-A2 platform fit: The MP-S-A2 cell is shared across several MyPhone handsets that use the same battery bay dimensions and connector pinout. Voltage rail at 3.7V nominal matches the charge IC spec on these boards, so the BMS handshake completes without error codes.
  • Bench tested on actual hardware: We cycled this cell through a full charge-discharge sequence and confirmed the BMS protection circuit trips correctly at both ends — low-voltage cutoff activated cleanly below 2.75V, and the overcharge threshold held at 4.2V without deviation.
  • Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Why the MyPhone reports wrong battery percentage after a cell swap

The fuel gauge IC on MyPhone handsets uses a coulomb counter calibrated to the original cell's internal resistance and discharge curve. A new cell has different characteristics, so the IC's stored model no longer matches actual cell behaviour. The phone may show 100% then drop rapidly, or stall at a fixed percentage for an extended period. One full uninterrupted discharge down to auto-shutdown, followed by a complete charge to 100%, forces the coulomb counter to rebuild its reference table against the new cell.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the modem radio or display fires a high-current draw and the cell voltage dips below the BMS cutoff threshold before the fuel gauge expects it. The reported percentage looks safe, but the cell's actual voltage under load has already hit the floor. It is not a defective cell — it is the fuel gauge IC still running on the old cell's discharge model. Run one full cycle as described above and the shutdowns will stop once the IC recalibrates its voltage-to-percentage mapping.

Replaces Part Numbers

MP-S-A2

Technical Specifications

Voltage3.7V
Amp Hours900mAh
Capacity900mAh
Rate3.33Wh
Net Weight16g /0.56 oz
Gross Weight41g /1.45 oz
Approximate Weight41g /1.45 oz
Dimension 53.00 x 34.00 x 4.80mm

Product Highlights

  • Brand: MyPhone
  • 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 MyPhone powers on fine but shuts off without warning at around 25% — is the new battery faulty?

The cell itself is not faulty. The fuel gauge IC is still using the discharge curve from the old cell, so it reads 25% while the actual cell voltage under screen or modem load has already dropped past the BMS cutoff. Run one full uninterrupted discharge to auto-shutdown, then charge to 100% without interruption — this forces the coulomb counter to recalibrate against the new cell. After that cycle, the shutdowns stop.

The phone is noticeably warm near the battery area while charging the new cell — is that normal?

A new cell starts with slightly higher internal impedance than a broken-in cell, so the charge IC dissipates more heat across the junction during the first few charge cycles. That warmth is expected and reduces after two or three full cycles as impedance settles. If the phone becomes hot enough to be uncomfortable to hold, interrupt the charge and let it cool before resuming. After the cell breaks in, charging temperature returns to normal levels.

The phone won't power on at all after the replacement battery sat in storage for a few months — how do I recover it?

Extended storage at low state-of-charge can push the cell below 2.5V per cell, triggering a BMS lockout that blocks normal charging. Connect the phone to a wall charger — not a USB port — and leave it for 20 to 30 minutes without pressing the power button. The charge IC applies a low-current trickle that slowly lifts the cell voltage back above the BMS re-enable threshold, typically around 2.9V, at which point normal charging resumes and the phone will boot.

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