Archos 40 Power AC40PO Compatible Battery 3.8V 1900mAh

Archos 40 Power — 3.8V Li-ion Replacement Battery (AC40PO)

This is a 3.8V, 1900mAh Li-ion battery for the Archos 40 Power smartphone. It replaces the original cell when the phone no longer holds a charge or shuts down unexpectedly. Capacity matches OEM spec at 7.22Wh.

• Archos 40 Power compatibility: The 40 Power uses a fixed connector pinout tied to the AC40PO part number. The BMS handshake runs over the same two-wire thermistor line as the original cell, so the phone's charge IC recognises the replacement without any modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 40 Power platform. The BMS accepted the charge IC handshake on the first cycle, and protection thresholds — overvoltage cutoff at 4.2V and undervoltage cutoff near 2.5V — triggered correctly at both limits.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins. Skipping this step causes the OS to read percentage from the old curve, which can produce erratic jumps or premature low-battery warnings.

Sudden shutdown at 20–30% on the Archos 40 Power

This is a voltage cliff failure. When the modem or screen draws high current, cell voltage sags below the BMS protection threshold before the fuel gauge reaches 0%. The phone cuts off because the cell cannot sustain load voltage — not because capacity is exhausted. It happens most often on aged cells but can also appear in the first few cycles on a new cell if the fuel gauge IC is still calibrated to the old cell's curve. Run one full discharge to shutdown, then a full charge to 4.2V, to anchor the coulomb counter to the new cell.

Phone not powering on after the battery sat in storage

Li-ion cells that sit discharged below roughly 2.5V per cell trigger BMS lockout — a protection state that blocks current flow until a minimum recovery voltage is applied. The 40 Power will show nothing on screen and will not respond to a short press of the power button. Connect the phone to a wall charger, not a PC USB port, and leave it for 15–20 minutes without pressing anything. The charge IC on the phone trickle-charges the cell back above the BMS recovery threshold, typically around 2.8V, at which point the BMS unlocks and normal charging resumes.