Doro 1378 DBAB-800A Replacement Battery 3.7V 900mAh

Doro 1378 / 1380 / 1382 / 1385 — 3.7V Li-ion Replacement Battery (DBAB-800A)

This is a 3.7V, 900mAh Li-ion replacement battery for the Doro 1378, 1380, 1382, and 1385 mobile phones. It replaces OEM part number DBAB-800A and fits directly into the existing battery bay. Use this when the original cell has degraded, lost charge capacity, or stopped holding a useful charge.

• Doro 1378 / 1380 / 1382 / 1385 compatibility: These four models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The DBAB-800A footprint — 53.00 × 34.00 × 4.30mm — fits all four without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Doro 1378. The BMS accepted the cell on first connection, charge termination triggered correctly at full voltage, and the protection circuit tripped as expected under a simulated short-load event.
• Fuel gauge recalibration on first use: After installing this cell, run one full discharge-to-charge cycle with fast charging disabled. The phone's fuel gauge IC is calibrated to the old cell's discharge curve. One complete cycle at standard charge current lets it recalibrate against the new cell before resuming normal charging behaviour.

Why the Doro 1378 reports wrong battery percentage after a cell swap

The Doro 1378 uses a fuel gauge IC that tracks charge state against a learned discharge curve from the previous cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry and internal resistance. The gauge reads against stale data, so the percentage shown on screen can be 10–20% off in either direction. One full discharge cycle — letting the phone reach auto-shutoff, then charging uninterrupted to 100% — forces the IC to rebuild the curve against the new cell. After that cycle, percentage readings stabilise.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated and the phone hits a voltage cliff before the reported percentage reaches zero. Under modem or screen load, the cell voltage drops sharply below the BMS cutoff threshold — around 3.0V — while the gauge still shows charge remaining. The phone shuts off because the hardware protection trips, not because the gauge said to. Run one complete discharge-charge cycle at standard current to re-anchor the coulomb counter to the new cell's actual low-voltage cutoff point. After calibration, the gauge triggers shutdown closer to 3.2–3.4V with the percentage reading in single digits rather than at 20–30%.