Archos 50b Oxygen AC50BOX Replacement Battery 3.7V 2000mAh

Archos 50b Oxygen / 50 Platinum — 3.7V Li-ion Replacement Battery (AC50BOX)

This is a 3.7V, 2000mAh Li-ion cell built to replace the original battery in the Archos 50b Oxygen, 50 Platinum, 50B Sauerstoff, and 50 Neon smartphones. It matches the OEM dimensions of 78.30 × 56.08 × 4.20 mm and drops into the same housing without modification. Part numbers AC50BOX, AC500BNE, and AC50NE 1ICP5/56/78 all cross-reference this cell.

• Multi-model fit — same cell, different names: The 50b Oxygen, 50 Platinum, 50B Sauerstoff, and 50 Neon share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. Archos sold these handsets across different markets under different names, but the internal cell spec did not change between them.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Archos platform and confirmed the BMS communicates correctly with the charge IC. The protection circuit tripped at the expected voltage floor and recovered cleanly on reconnection.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-to-charge cycle before enabling high-current charging again. This lets the fuel gauge IC map the new cell's actual discharge curve before the coulomb counter starts tracking capacity against an uncalibrated baseline.

Sudden shutdown at 20–30% on the Archos 50b Oxygen after a cell swap

This happens when the fuel gauge IC is still referencing the discharge curve of the old, degraded cell. A new cell has a steeper voltage cliff near depletion — the modem or screen pulls current, voltage sags briefly below the protection threshold, and the phone cuts off even though reported charge looks healthy. The BMS is doing exactly what it should. Running one full discharge cycle from 100% down to automatic shutdown, then charging to 100% uninterrupted, forces the coulomb counter to rebuild its curve against the new cell. After that cycle, shutdowns at 20–30% typically stop.

Phone shows erratic percentage jumps after fitting the replacement cell

Percentage jumping — say, from 45% to 61% or dropping 10 points instantly — points directly to a fuel gauge IC that has not yet characterised the new cell. The IC stored learned parameters from the old degraded cell and is applying them to a different discharge profile. Force a calibration cycle: drain the phone until it shuts off automatically, leave it off for five minutes, then charge uninterrupted to 100% with the screen off. Most Archos units stabilise the percentage readout within two full cycles after that.