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Master MF01 Replacement Battery 3.7V 900mAh Li-ion

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From $23.99 USD $29.99
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Fits Master MF01, MF015, MF016 DUAL SIM, and MF021S smartphones with OEM battery compatibility confirmed across all listed variants.
3.7V and 900mAh capacity deliver standard smartphone runtime on the Master platform without voltage sag under modem load.
Connector type matches OEM contact layout; locking tab engages flush with battery door and seats without force.
We ran a full discharge curve on the bench — BMS accepted charge from USB without fault codes; voltage remained stable under screen and modem draw.
On first use after installation, disable fast charging for one complete discharge-charge cycle so the fuel gauge IC recalibrates against this cell's discharge curve before high-current charging.
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

3.7V

Amp

900mAh

Master MF01 / MF015 / MF016 Dual SIM / MF021S — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion cell for Master smartphones including the MF01, MF015, MF016 Dual SIM, and MF021S. It fits phones where the original cell has lost capacity or stopped holding a charge. Dimensions are 53.00 × 34.00 × 4.80mm — confirm against your existing cell before installing.

  • MF01 series compatibility: These models share the same physical footprint, connector pinout, and 3.7V nominal voltage rail. The BMS on each accepts the same charge termination voltage, so one cell covers the group without modification.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the MF01 platform. The BMS accepted the full charge cycle, and the protection circuit tripped correctly at the low-voltage cutoff — no unexpected shutdowns during controlled load testing.
  • Fuel gauge recalibration after swap: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's actual discharge curve before the OS starts reporting percentages it can trust.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff problem, not a defective cell. When the screen or modem draws a high current spike, the replacement cell's internal resistance causes a brief voltage drop. If that drop crosses the BMS cutoff threshold — typically around 3.0V — the phone shuts off even though the fuel gauge still shows charge remaining. The fix is one full discharge-charge cycle so the fuel gauge IC recalibrates its curve to the new cell. After calibration, the reported percentage and actual cell voltage align, and the phantom shutdowns stop.

Phone reports wrong battery percentage after cell swap

The OS fuel gauge IC stores a learned discharge curve from the old cell. A new cell with different impedance characteristics makes that stored curve inaccurate, so the percentage reading drifts or jumps. Run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% without fast charging enabled. That single cycle gives the coulomb counter enough data to rebuild an accurate state-of-charge map against the new cell's actual behaviour.

Compatible Models

MF01 MF015 MF016 DUAL SIM MF021S MF024

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: Master
  • 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 Master MF01 won't turn on at all after the replacement battery sat in a drawer for a few months — is the cell dead?

It's likely a BMS lockout, not a dead cell. Li-ion cells that self-discharge below roughly 2.5V in storage trigger the protection circuit, which cuts output to prevent damage. Connect the phone to a wall charger — not a PC USB port — and leave it for 20–30 minutes without pressing the power button. The charge IC needs to trickle current into the cell until it climbs above the BMS recovery threshold, typically around 2.8–3.0V, before the phone will respond.

Fast charging stopped working after I fitted this replacement — my phone used to charge quickly but now it's slow.

On the first cycle after a cell swap, the phone's charging IC sometimes falls back to standard charge rates because it hasn't yet negotiated the full USB protocol handshake with the new BMS. Plug in using the original charger and cable, let it complete one full charge to 100% at the slower rate, then unplug and discharge normally. On the second cycle, fast charging typically re-engages once the charge IC confirms the new cell is accepting current within expected parameters.

The phone feels warm near the battery compartment while charging — is that normal with a new cell?

Some warmth on the first few charge cycles is expected. A fresh cell has slightly higher internal impedance than a broken-in one, so the charge IC dissipates a little more energy as heat during constant-current phase. If the phone is uncomfortable to hold or the warmth persists past the third full charge cycle, check that the replacement cell connector is fully seated — a partial connection raises contact resistance and increases heat at the joint. Normal operating temperature during charging should settle below 40°C after break-in.

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