BB92100 SoftBank S31HT Compatible Battery 3.7V 1100mAh

SoftBank S31HT — 3.7V Li-ion Replacement Battery (BB92100)

This is a 3.7V Li-ion cell rated at 1100mAh (4.07Wh), built to fit the SoftBank S31HT smartphone. It replaces OEM part numbers BB92100, 35H00137-00M, and BA S430. If your S31HT shuts down unexpectedly, no longer holds charge, or won't power on, this cell is the direct swap.

• S31HT compatibility: The S31HT uses a compact 45.66 × 41.78 × 6.20mm cell format with a specific connector pinout. All three OEM part numbers reference the same physical cell and BMS handshake — this replacement matches that spec exactly.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the S31HT platform. The BMS accepted the charge IC handshake cleanly, and the protection circuit tripped correctly at the low-voltage cutoff threshold without false triggers during normal use.
• Fuel gauge recalibration on first use: On first install, disable fast charging and run one full discharge-to-charge cycle. The S31HT's fuel gauge IC is calibrated to the previous cell's discharge curve — letting it map the new cell under a slow, steady cycle prevents the percentage counter from jumping erratically in the first week.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity problem. When the S31HT runs the modem and display simultaneously, current draw spikes sharply. If the fuel gauge IC hasn't mapped the new cell's discharge curve yet, it reads remaining capacity too optimistically. The cell voltage drops below the BMS cutoff threshold under load before the OS registers a low battery warning. Run one full discharge cycle without fast charging — let the phone reach 5% or below on its own — then charge to 100% to reset the coulomb counter baseline.

Battery percentage jumping erratically after install

The S31HT's fuel gauge IC stores a learned discharge model tied to the old cell's internal resistance profile. A new cell has a different impedance curve, so the IC miscalculates state-of-charge and reports jumpy or inconsistent percentages. This isn't a fault with the replacement cell — it's the gauge recalibrating. Complete two full discharge-charge cycles (slow charge, no fast charging) and the reported percentage will stabilise to within a few percent of actual capacity.