HTC Desire C Replacement Battery 3.7V 1300mAh BA S840

HTC Desire C / Desire 200 — 3.7V Li-ion Replacement Battery (BA S840)

This is a 3.7V, 1300mAh Li-ion replacement battery for the HTC Desire C, Desire 200, Golf, and A320E smartphones. It fits devices that use OEM part numbers BA S840, BA S850, or 35H00194-00M. Drop the original out, slide this in — the connector and form factor match the stock battery bay.

• Desire C / Desire 200 platform fit: These models share the same battery bay dimensions (53.20 × 42.90 × 4.70mm), voltage rail, and connector pinout. One cell covers the full compatibility group without modification.
• Bench tested on actual hardware: We ran this cell through a full discharge-charge cycle on a Desire C unit. The BMS accepted charge handshake on the first connection, held voltage above 3.6V under combined screen and modem load, and tripped the protection circuit correctly at the low-voltage threshold.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before you resume normal use.

Why the Desire C reports wrong battery percentage after a cell swap

The Desire C uses a fuel gauge IC that learns the discharge curve of whichever cell is installed. When you fit a new battery, the IC is still calibrated to the old cell's internal resistance and capacity curve. It takes one full discharge-to-charge cycle for the coulomb counter to reset and re-map against the new cell. Until that cycle completes, percentage readings can appear frozen, inflated, or jumping by 5–10% at a time. Run the phone down to auto-shutdown once, then charge uninterrupted to 100% — the gauge stabilises after that.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem's minimum operating threshold under peak load — typically during a call, video stream, or GPS fix — even though the gauge still reads 20–30%. The fuel gauge IC hasn't yet learned the new cell's voltage sag characteristics, so it doesn't warn the OS early enough. The BMS trips as cell voltage dips below roughly 3.2V under load. One full recalibration cycle resolves this by giving the IC accurate data to trigger a low-battery warning before voltage collapses.