MyPhone MP-S-I 1050 Replacement Battery 3.7V 1050mAh

MyPhone 1050 — 3.7V Li-ion Replacement Battery (MP-S-I)

This is a 3.7V, 1050mAh Li-ion cell for the MyPhone 1050 smartphone. It replaces the original MP-S-I battery when the existing cell has degraded, swells, or no longer holds a usable charge. Dimensions are 55.42 × 35.01 × 5.41mm — measure your bay before installing if the original has expanded.

• MyPhone 1050 fitment: The 1050 uses a fixed voltage rail at 3.7V with a connector and contact layout matched to the MP-S-I form factor. Swapping to any cell outside this voltage range will cause the charge IC to reject the battery or fail to regulate correctly.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a 3.7V Li-ion test rig, confirming BMS cutoff at both the low-voltage floor and charge termination voltage. Cell voltage at rest settled at 3.85V after a full charge cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and complete one full discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the charge IC pushes higher current into an uncalibrated cell.

Sudden shutdown at 20–30% on the MyPhone 1050 after a cell swap

A new cell has a slightly different voltage-versus-capacity curve than the original. The fuel gauge IC still holds the old curve in memory, so it misreads how much charge remains. When the modem or display pulls a current spike, the cell voltage drops below the BMS cutoff threshold — even though the reported percentage looks safe. The phone shuts off to protect the cell. One full discharge-to-charge cycle forces the coulomb counter to recalibrate against the new cell, and the shutdowns stop.

MyPhone 1050 not powering on after the replacement battery sat in storage

Li-ion cells self-discharge in storage. If the cell voltage drops below approximately 2.5V, the BMS enters a lockout state and blocks current flow entirely — the phone will not respond to the power button or a charger. Connect the phone to a low-current USB source and leave it for 15–30 minutes without pressing anything. The charge IC will trickle current into the cell until it clears the lockout threshold, after which normal charging resumes. If the phone still shows no response after 30 minutes, verify the charger is delivering at least 5V with a USB meter.