MyPhone Flip 3 Compatible Battery BS-18 3.7V 900mAh

MyPhone Flip 3 — 3.7V Li-ion Replacement Battery (BS-18)

This is a 3.7V, 900mAh (3.33Wh) lithium-ion cell that fits the MyPhone Flip 3 and Flip III smartphones. It replaces the original BS-18 battery when the phone can no longer hold a charge or fails to power on. Dimensions are 46.47 x 39.79 x 5.33mm — confirm these against your existing cell before installation.

• Flip 3 and Flip III compatibility: Both model names refer to the same hardware platform. The BS-18 cell uses the same connector pinout and voltage rail across both variants, so one replacement covers either unit.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Flip 3 platform. The BMS accepted the cell without rejecting it as an unrecognised unit, and charge termination triggered correctly at full capacity.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before any high-current charging session.

Sudden shutdown at 20–30% on a replacement cell

The Flip 3's fuel gauge IC stores a discharge curve calibrated to the original cell. A new cell has a slightly different internal resistance profile, which means the voltage reported to the OS drifts from the real cell voltage under load. When the modem or screen draws current, the cell voltage dips faster than the gauge predicts, and the phone shuts down before the displayed percentage reaches zero. One full discharge-charge cycle with fast charging off forces the coulomb counter to recalibrate against the new curve. After that cycle, shutdowns at 20–30% typically stop.

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

Lithium-ion cells self-discharge during storage. If the BS-18 cell drops below approximately 2.5V, the BMS trips into lockout to prevent cell damage — and the phone shows nothing when you press the power button. Connect the phone to a charger and leave it for 15–20 minutes before attempting to power on. The charge IC needs time to trickle current into a deeply discharged cell before the BMS will release the lockout and allow normal boot.