SFR S 300+ Compatible Battery 3.7V 2400mAh 35H00077-00M

SFR S 300+ — 3.7V Li-Polymer Replacement Battery (35H00077-00M)

This is a 3.7V, 2400mAh lithium-polymer cell that replaces the original battery in the SFR S 300+ smartphone. It fits the S 300+ directly, matching the OEM voltage and connector spec. Capacity figures come from the product data: 2400mAh / 8.88Wh.

• S 300+ platform fit: The S 300+ uses a single-cell Li-Polymer pack at 3.7V nominal. This cell matches that voltage rail, the OEM connector pinout, and the BMS handshake the charge IC expects. Part numbers 35H00077-00M, TRIN160, and 35H00077-02M all cross to this cell.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the S 300+ platform. The BMS accepted the cell without fault codes, the charge IC stepped through CC/CV stages correctly, and the fuel gauge IC began tracking state-of-charge within the first full cycle.
• First-cycle fast charge tip: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current fast charging pushes into an uncalibrated cell.

Sudden shutdown at 20–30% on the S 300+ after a cell swap

A new Li-Polymer cell has a slightly different voltage-to-capacity curve than the worn cell it replaces. The fuel gauge IC on the S 300+ still holds calibration data from the old cell. When the new cell hits roughly 3.5–3.6V under modem or display load, voltage drops faster than the IC expects, and the phone cuts out before the percentage reaches zero. One full discharge-to-shutdown followed by an uninterrupted charge to 100% forces the coulomb counter to re-anchor to the new cell's actual curve. After that cycle, the shutdowns stop.

OS reporting wrong battery percentage after replacement

The S 300+ fuel gauge IC stores learned capacity data from the previous cell across power cycles. Drop in a new 2400mAh cell and that stored data is immediately wrong — the percentage display can jump, stall, or read 100% for far longer than it should. The fix is a hard recalibration: drain the phone until it shuts itself off, then charge it uninterrupted to 100% with the screen off. After one full cycle the IC resets its reference points to the new cell, and percentage reporting stabilises to within a few percent of actual charge state.