About this replacement
MyPhone 6670 City — 3.7V Li-ion Replacement Battery (MP-S-G)
This 3.7V 950mAh Li-ion cell replaces the OEM MP-S-G battery in the MyPhone 6670 City smartphone. It restores power to calling, messaging, and app functions when the original cell has degraded or failed. Dimensions are 47.35 × 37.92 × 5.50mm — confirm these against your existing cell before fitting.
- MyPhone 6670 City fit: This cell matches the voltage rail, physical footprint, and connector orientation the 6670 City mainboard expects. The BMS communicates charge state to the phone's fuel gauge IC using the same protocol as the original MP-S-G unit.
- Bench tested on actual hardware: We cycled this cell through full charge and load discharge on the bench. The BMS held cutoff correctly at the low-voltage threshold and accepted charge current without tripping protection on the first cycle.
- First-cycle calibration on the 6670 City: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. The fuel gauge IC in the 6670 City calibrates its coulomb counter against the new cell's discharge curve — skipping this step causes the percentage readout to drift by up to 15% in normal use.
Sudden shutdown at 20–30% on the MyPhone 6670 City after a cell swap
The 6670 City's fuel gauge IC maps percentage to voltage using curves stored from the previous cell. A new 950mAh cell has a slightly different voltage-capacity profile, so the phone underestimates how close the cell is to its lower cutoff. When the modem fires a high-current burst during a call or data sync, the cell voltage dips below the BMS cutoff threshold — even though the screen shows 25%. One full discharge-charge cycle lets the coulomb counter rebuild its internal map against the new cell. After that cycle, shutdowns at false-high percentages stop.
MyPhone 6670 City not powering on after the replacement battery sat in storage
Li-ion cells self-discharge during storage. If this battery sat for several months before installation, its resting voltage may have dropped below 2.5V — the point where the BMS latches into lockout to prevent cell damage. The phone will show no response to the power button and may not register on a charger immediately. Connect the phone to a wall charger and leave it for 15–20 minutes without pressing anything — the charge IC trickle-charges the cell back above 2.9V, which releases the BMS lockout and allows a normal boot.