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MeiZu M3s BT15 Replacement Battery 3.85V 2800mAh

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From $23.99 USD $29.99
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Fits MeiZu M3s and replaces OEM battery part number BT15 directly.
Voltage is 3.85V at 2800mAh capacity — this matches the original cell rating for standard smartphone runtime without overdraw stress.
Connector is soldered to the device mainboard with a two-pin JST alignment — no slot or tab, physical fit is fixed orientation only.
We bench-tested this pack on a Y685M motherboard simulator; the BMS accepted full charge cycles without early cutoff or thermal drift.
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 discharge curve before high-current charging pushes current into an uncalibrated cell.
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

3.85V

Amp

2800mAh

MeiZu M3s / Y685 Series — 3.85V Li-Polymer Replacement Battery (BT15)

This is a 3.85V, 2800mAh lithium-polymer cell replacing the OEM BT15 battery in the MeiZu M3s and Y685 series smartphones (Y685C, Y685M, Y685Q). It fits the original battery bay without modification and connects to the same flex ribbon connector as the factory unit. Capacity is rated at 10.78Wh.

  • M3s and Y685 platform fit: The M3s and Y685 variants share the same physical footprint (70.92 × 59.60 × 3.58mm), the same 3.85V nominal rail, and the same BT15 BMS connector pinout — so one cell covers all listed models without adapter or modification.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the M3s mainboard, confirmed the BMS handshake completed correctly, and verified the charge IC accepted the full 2800mAh without triggering a protection cutoff.
  • First-cycle fuel gauge reset: After installation, disable fast charging and run one complete discharge-to-charge cycle at standard current. The M3s fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve during this first pass — skipping it causes the percentage display to drift for days.

Why the M3s reports wrong battery percentage after a cell swap

The M3s uses a fuel gauge IC that builds its battery model from accumulated charge and discharge data. When you swap the cell, that stored model still reflects the old cell's impedance and capacity curve. The IC feeds the OS percentage figures based on a curve that no longer matches the new cell. One full slow-rate discharge-to-charge cycle gives the coulomb counter enough data to re-anchor its calculations to the replacement cell.

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

This happens when the modem or display spikes current demand and the cell voltage drops sharply — faster than the fuel gauge IC predicted. The phone's protection circuit reads that voltage cliff as a dead cell and shuts down, even though the percentage display said 25%. It is more noticeable on a fresh replacement because the fuel gauge curve is still uncalibrated. Run two full discharge-charge cycles at standard rate and confirm the cell voltage at shutdown reads no lower than 3.4V using a USB voltage logger or the phone's engineering mode.

Compatible Models

M3s Y685C Y685M Y685Q Y685H Meilan 3s

Replaces Part Numbers

BT15

Technical Specifications

Voltage3.85V
Amp Hours2800mAh
Capacity2800mAh
Rate10.78Wh
Net Weight37g /1.31 oz
Gross Weight62g /2.19 oz
Approximate Weight62g /2.19 oz
Dimension 70.92 x 59.60 x 3.58mm

Product Highlights

  • Brand: MeiZu
  • 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 MeiZu M3s powers off at around 25% after putting in the new battery — is the cell faulty?

The cell is almost certainly fine. The fuel gauge IC on the M3s is still using the discharge curve it built for the old, degraded cell, so it misjudges the voltage drop under modem or screen load and triggers a shutdown before the cell is actually empty. Run two complete discharge-charge cycles at the standard charge rate without fast charging enabled. After that recalibration, the shutdowns should stop; if the phone still cuts out below 3.4V cell voltage, the replacement cell itself may have a weak cell and should be exchanged.

Fast charging stopped working after I replaced the battery on my M3s — the phone only slow charges now.

This is a BMS initialisation behaviour on the first cycle after a cell swap. The M3s charge IC performs a handshake with the battery BMS before allowing high-current charging, and on a fresh cell that handshake sometimes defaults to trickle mode until one standard charge cycle completes. Plug in using the original charger and cable, let it charge fully at whatever rate it accepts, then unplug and replug — fast charge should re-engage. If it does not after two full cycles, check that the battery flex connector is fully seated, as a partially connected ribbon disrupts the BMS signal line.

The M3s gets noticeably warm near the battery while charging the new cell — is that normal?

Some warmth is expected on the first few charges of a fresh lithium-polymer cell. A brand-new cell has slightly higher internal impedance than a broken-in cell, so the charge IC dissipates a little more energy as heat during the constant-current phase. That warmth should reduce after three to four full cycles as the cell's impedance settles. If the phone stays hot to the touch throughout the entire charge session after several cycles, check that the battery flex cable is not pinched under the midframe, as a bent ribbon can cause abnormal resistance and sustained heat at the charge IC.

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