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McGrey MC-50B Replacement Battery 3.7V 1200mAh Li-ion

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From $23.99 USD $29.99
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Fits McGrey MC-50B smartphone; replaces OEM battery CS-DEP215SL.
3.7V, 1200mAh lithium-ion cell restores full capacity to the MC-50B after original pack degradation.
Connector type and slot orientation match OEM hardware; no modification needed during installation.
Bench testing showed BMS acceptance on first insertion with no cutoff faults or voltage drift.
On first charge cycle after installation, disable fast charging — let the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging resumes.
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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

1200mAh

McGrey MC-50B — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1200mAh Li-ion battery for the McGrey MC-50B smartphone. It fits the MC-50B directly and restores power when the original cell has degraded past usable capacity. Dimensions are 53.00 × 33.90 × 5.70mm — confirm these against your existing cell before fitting.

  • MC-50B cell compatibility: The MC-50B runs a single-cell 3.7V nominal architecture. This replacement matches that voltage rail and physical footprint, so the charge IC sees the correct cell parameters at startup.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on a smartphone test rig, confirming BMS handshake, charge acceptance from 0%, and stable voltage at the protection cutoff threshold.
  • Fuel gauge recalibration after swap: On first use after installation, disable fast charging for one full discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the MC-50B after a cell swap

A new cell has a slightly different internal resistance profile than the aged cell the fuel gauge IC was calibrated to. Under screen or modem load, the cell voltage drops faster than the gauge predicts, hitting the hardware cutoff before the displayed percentage reaches zero. The phone sees a hard voltage floor — not a software decision — and shuts down immediately. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and pushes the shutdown threshold back down to the correct level.

MC-50B not powering on after the replacement cell sat in storage

Li-ion cells self-discharge during storage, and if voltage drops below roughly 2.5V the BMS trips into lockout to prevent damage to the cell. The phone will show no response on the power button — not even a charge indicator. Connect to a wall charger, not a USB port, and leave it for 15–20 minutes before attempting to power on. Once the BMS sees voltage climb above its recovery threshold, typically around 2.9–3.0V, it releases the lockout and normal charging resumes.

Compatible Models

MC-50B

Technical Specifications

Voltage3.7V
Amp Hours1200mAh
Capacity1200mAh
Rate4.44Wh
Net Weight31g /1.09 oz
Gross Weight56g /1.98 oz
Approximate Weight56g /1.98 oz
Dimension 53.00 x 33.90 x 5.70mm

Product Highlights

  • Brand: McGrey
  • 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

The McGrey MC-50B shows 25% battery and then just cuts off with no warning — is the new cell faulty?

This is a voltage cliff, not a faulty cell. The fuel gauge IC is still calibrated to the old cell's discharge curve, so it misreads remaining capacity under load — the modem or screen pulls enough current to crash cell voltage below the hardware cutoff before the counter reaches zero. Run one complete discharge-to-shutdown cycle followed by a full uninterrupted charge to 100%, and the coulomb counter will realign to the new cell.

Fast charging stopped working on the MC-50B after fitting the replacement battery — the phone only trickle charges now.

On the first cycle after a cell swap, the charge IC often defaults to trickle or standard charge rates while it validates the new cell's impedance profile. This is a deliberate safety step, not a fault. Let the phone complete one full charge at the slower rate without interrupting it. Fast charge typically resumes from the second cycle once the IC has logged a clean baseline from the new cell.

The MC-50B battery percentage is jumping around erratically — it reads 60%, drops to 41%, then jumps back up.

The fuel gauge IC uses a coulomb counter tied to the old cell's discharge model, and a new cell with different impedance throws that model off. The percentage readout becomes unreliable until the IC collects enough cycle data to update its reference curve. Fully discharge the phone until it shuts itself off, then charge to 100% in one uninterrupted session — do this twice if the jumping continues. After two full cycles the gauge stabilises against the new cell's actual characteristics.

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