About this replacement
Anbernic RG505 — 3.7V Li-Polymer Replacement Battery (FL606090)
This is a 3.7V, 5000mAh Li-Polymer cell carrying part number FL606090. It fits the Anbernic RG505 handheld retro gaming console. It replaces a degraded or failed original cell and restores untethered play.
- RG505 fitment: The RG505 runs a single-cell Li-Polymer pack on a 3.7V nominal rail. The FL606090 cell dimensions — 92.40 × 60.00 × 6.30 mm — match the battery bay exactly. The connector pinout and BMS communication lines align with the console's charge IC without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the RG505 platform. The BMS accepted the cell without triggering overcurrent or NTC fault flags. Charge termination cut off cleanly at 4.2V as expected.
- Fuel gauge calibration on first install: After fitting this cell, run one complete play session to automatic low-battery cutoff before recharging. The RG505 fuel gauge IC sets its empty reference point against the first full discharge cycle. Skipping this step causes the percentage indicator to read high and shut down unexpectedly.
Why the RG505 fuel gauge jumps or reads incorrectly after a cell swap
The RG505 uses a coulomb-counting fuel gauge IC that tracks charge relative to a stored discharge curve. When you fit a new cell, that stored curve no longer matches the new cell's actual chemistry profile. The gauge will show erratic percentages — jumping from 80% to 30% mid-session — until it recalibrates. One full discharge to cutoff followed by a full charge resets the reference and stabilises the readout.
Console shuts down suddenly while the battery indicator still shows charge remaining
This happens when the cell voltage sags below the BMS cutoff threshold under load, even though the fuel gauge still displays a non-zero percentage. On the RG505, running demanding emulation cores pushes higher current draw, which accelerates voltage sag on a partially discharged cell. A new cell that hasn't completed conditioning cycles will sag earlier than the gauge predicts. After 3–5 full charge and discharge cycles, the cell's internal resistance drops and the voltage sag under load reduces — unexpected shutdowns typically stop after that.