BlackBerry C-S2 Compatible Battery 3.7V 1900mAh Li-ion

BlackBerry 8700f Series — 3.7V Li-ion Replacement Battery (C-S2)

This is a 3.7V, 1900mAh Li-ion cell built to the C-S2 specification. It fits the BlackBerry 8700f, 8700g, 8705g, and 8707g smartphones. Voltage and connector match the original BAT-06860-003 factory spec exactly.

• 8700-series platform fit: The 8700f, 8700g, 8705g, and 8707g all share the same battery bay dimensions, connector pinout, and 3.7V charge rail. One cell covers the full lineup because the BMS handshake protocol and charge termination voltage are identical across these variants.
• Bench tested on actual hardware: We ran this cell in an 8700g chassis. The BMS accepted charge immediately, charge termination triggered correctly at 4.2V, and the protection circuit tripped as expected under a short-circuit load test. No anomalies at full charge or near-empty cutoff.
• Fuel gauge recalibration on first use: After installing this cell, run one complete discharge down to auto-shutdown, then charge uninterrupted to 100%. The 8700 series fuel gauge IC calibrates its coulomb counter against the actual discharge curve on that first full cycle — skipping it causes inaccurate percentage readings for weeks.

Sudden shutdown at 20–30% on the 8700 series after a cell swap

The 8700f's fuel gauge IC holds a discharge curve map calibrated to the original cell. A new cell with a slightly different internal resistance profile causes the IC to miscalculate the voltage cliff — the point where cell voltage collapses under GSM radio or screen load. The phone interprets a momentary voltage sag as a dead cell and shuts down, even though charge remains. One full discharge-to-shutdown followed by an uninterrupted full charge resets the curve map and eliminates the false cutoff.

8700f not powering on after the battery sat in storage

Li-ion cells self-discharge in storage. If this battery shipped or sat unused long enough to drop below 2.5V per cell, the BMS enters lockout mode and blocks all current flow to protect the cell from damage. The phone will not respond to the power button and may not register on a standard charger. Connect to a charger and leave it for 20–30 minutes without pressing anything — most BMS circuits include a trickle-charge recovery path that slowly raises cell voltage back above the lockout threshold, typically 2.9V, before allowing normal charge current to resume.