MyPhone C-Smart BM-03 Compatible Battery 3.7V 1500mAh

MyPhone C-Smart / Funky — 3.7V Li-ion Replacement Battery (BM-03)

This is a 3.7V, 1500mAh Li-ion battery carrying OEM part number BM-03. It fits the MyPhone C-Smart and Funky smartphones. It replaces the original cell when capacity has dropped and the phone no longer holds a useful charge.

• C-Smart and Funky compatibility: Both models use the same battery bay dimensions, voltage rail, and BMS connector pinout. The BM-03 cell measures 57.30 × 54.05 × 4.60mm — a physical fit that matches both devices without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the C-Smart platform. The BMS accepted the cell, completed a full charge without interruption, and held voltage above the low-battery cutoff threshold through the discharge curve.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the first day.

Sudden shutdown at 20–30% on a replacement cell

This is a voltage cliff, not a capacity problem. When the modem transmits or the screen peaks in brightness, current draw spikes sharply. A new cell with an uncalibrated fuel gauge IC can report 25% remaining while actual cell voltage has already dropped below the 3.2V cutoff threshold. The BMS trips, and the phone shuts off before the percentage reaches zero. One full discharge-charge cycle without fast charging recalibrates the coulomb counter and eliminates this behaviour.

Phone won't power on after the battery sat in storage

Li-ion cells that discharge below approximately 2.5V per cell trigger a BMS lockout — the protection circuit opens and blocks current to prevent damage. Plugging in the charger may show nothing on screen for several minutes. Leave the phone connected to a wall charger, not a USB port, for at least 20–30 minutes without pressing the power button. Once the cell recovers above the BMS re-enable threshold, the phone will boot normally.