About this replacement
Siemens M300 / M100 / M315 / M220 — 3.7V Li-ion Replacement Battery
This is a 3.7V, 700mAh Li-ion battery for the Siemens M300, M100, M315, and M220 mobile phones. These four models share the same battery bay dimensions and cell format — 52.61 × 34.40 × 6.45mm — so one SKU covers all four. Voltage and capacity match the original factory specification.
- M300, M100, M315, M220 compatibility: All four phones use the same physical cell size and 3.7V single-cell Li-ion voltage rail. The connector pinout and BMS charge handshake are consistent across the range, so no adapters or modifications are needed when swapping between these models.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the M300 platform. The BMS accepted charge termination cleanly at 4.2V and cut off discharge at the low-voltage threshold without triggering any unexpected shutdowns during normal load.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging if your charger supports it and run one complete discharge-charge cycle before heavy use. This allows the fuel gauge IC to map the new cell's discharge curve before it reports percentage readings to the OS.
Sudden shutdown at 20–30% on the Siemens M300 after a cell swap
This is a voltage cliff issue. At 20–30% state-of-charge, a new cell's internal impedance can cause a brief voltage drop under modem or display load — enough to cross the BMS cutoff threshold even though capacity remains. The fuel gauge IC is still calibrated to the old cell's discharge curve, so it misreads remaining charge. One full discharge-charge cycle resets the coulomb counter and resolves premature shutdowns on most units.
Phone shows incorrect battery percentage after replacement cell installed
The fuel gauge IC stores a learned discharge curve from the previous cell. When a new cell goes in, that stored curve no longer matches the actual cell characteristics, so percentage readings appear wrong or jump erratically. Drain the battery until the phone shuts off, then charge uninterrupted to 100% without interruption. After one full cycle the coulomb counter recalibrates and percentage accuracy stabilises.