RCB571 Doro Primo 571 Replacement Battery 3.7V 1300mAh

Doro Primo 571 — 3.7V Li-ion Replacement Battery (RCB571)

This is a 3.7V, 1300mAh Li-ion cell built to the RCB571 spec for the Doro Primo 571. The Primo 571 is a senior-focused basic mobile phone with a fixed back cover — the battery is user-replaceable but the slot is exact-fit only. Dimensions are 60.00 x 43.80 x 4.50mm, matching the original cell cavity.

• Primo 571 fit: The Primo 571 uses a dedicated slot with a keyed connector tab. Only cells cut to the RCB571 footprint seat flush and make full contact with the charging pins. An undersized or oversized cell will not close the battery cover or register on the charge circuit.
• Bench tested on actual hardware: We cycled this cell through full charge and load discharge on the Primo 571 platform. The BMS accepted the cell without fault flags, and the charge IC stepped through trickle, CC, and CV phases cleanly.
• Fuel gauge recalibration on first install: After fitting this cell, run one complete discharge to auto-off, then charge uninterrupted to 100% before normal use. The Primo 571's fuel gauge IC holds the old cell's discharge curve in memory — skipping this step causes the percentage readout to jump erratically in the first few days.

Sudden shutdown at 20–30% on the Primo 571

The Primo 571 shuts down mid-use even when the indicator shows charge remaining because the fuel gauge IC is still mapped to the old cell's voltage-discharge curve. A fresh 1300mAh cell hits a steeper voltage drop under GSM modem transmit load than a worn cell does — the phone's low-voltage cutoff trips before the displayed percentage reaches zero. One full discharge-charge cycle forces the coulomb counter to re-anchor to the new cell's actual curve. After that cycle, the shutdown point drops back to near 0%.

Phone warm near the battery door during first charge

A new cell arrives with higher internal impedance than a broken-in cell. During the first few charge cycles, the Primo 571's charge IC pushes current into that higher-impedance cell, and the extra resistive heating is noticeable through the back cover. This is normal for the first two to three cycles and settles as the cell's impedance drops. If the cover stays hot after three full cycles, check that the battery door is fully seated — a partially closed cover traps heat against the cell.