Li3720T43P4h825839 Orange Reyo Replacement Battery 3.8V 2000mAh

Orange Reyo — 3.8V Li-ion Replacement Battery (Li3720T43P4h825839)

This is a 3.8V, 2000mAh Li-ion battery for the Orange Reyo smartphone. It matches the OEM part number Li3720T43P4h825839 and fits directly into the Reyo's battery bay. Capacity is 7.6Wh — identical to the original cell specification.

• Orange Reyo fit: The Reyo uses a single-cell 3.8V Li-ion pack with a specific connector pitch and BMS handshake tied to the phone's charge IC. This replacement meets that voltage rail and connector spec, so the charge IC accepts it without throwing a battery error.
• Bench tested on actual hardware: We ran charge and discharge cycles on this cell using a programmable load to verify BMS cutoff thresholds. The protection circuit tripped correctly at low-voltage cutoff and released on resume charge — no latched lockout observed.
• Fuel gauge recalibration on first cycle: After fitting this cell, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the Reyo's fuel gauge IC a clean reference curve against the new cell before normal use resumes.

Why the Reyo reports wrong battery percentage after a cell swap

The Reyo uses a coulomb counter inside the fuel gauge IC that builds its percentage model from learned discharge curves on the original cell. Swapping the cell resets nothing in the IC — it keeps applying the old curve to a new cell with a different internal resistance profile. This mismatch causes the percentage to read high, then drop suddenly. One full uninterrupted discharge-charge cycle forces the IC to relearn the curve against the replacement cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — typically during an LTE transmission burst or screen-on peak draw — before the fuel gauge IC registers the drop in percentage. The phone shuts down because the SoC brown-out threshold is hit, not because the reported percentage reached zero. A degraded or uncalibrated cell hits this voltage cliff earlier than the gauge predicts. Run the recalibration cycle first; if shutdowns persist, check that the battery connector is fully seated and the contact strip is clean before ruling out a faulty cell.