Archos A55 Helium Replacement Battery AC55HEP 3.7V 2300mAh

Archos A55 Helium / Helium+ — 3.7V Li-ion Replacement Battery (AC55HEP)

This 3.7V, 2300mAh (8.51Wh) lithium-ion battery replaces the original AC55HEP cell in the Archos A55 Helium and Helium+. It fits directly in either model — both share the same battery bay, connector, and BMS handshake. Use this when the original cell no longer holds a usable charge or fails to power the device through normal daily tasks.

• A55 Helium and Helium+ compatibility: Both models run the same 3.7V battery rail with an identical connector and BMS communication protocol. One cell fits both. No hardware modification needed.
• Bench tested on actual hardware: We cycled this cell through a full discharge-charge sequence and confirmed the BMS handshake completes correctly. Charge acceptance was stable across the full 3.7V nominal range with no cutoff anomalies at the top or bottom of the curve.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes load into an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the A55 Helium after a cell swap

The A55 Helium's fuel gauge IC holds the discharge curve of the old cell in memory. When a new cell is installed, the IC applies the old curve to the new cell — which has a different internal resistance profile. Under modem or screen load, the phone's voltage rail sags below the IC's shutdown threshold before the reported percentage reaches zero. This is not a faulty cell. One full discharge-charge cycle without fast charging resets the coulomb counter and maps the new curve. After that cycle, shutdowns at elevated percentages stop.

USB fast charge not activating on the first cycle after replacement

After a cell swap, the charge IC sometimes declines the fast-charge handshake on the first cycle because it reads the new cell's higher impedance as an out-of-spec condition. The A55 Helium's charge controller defaults to standard 5V/1A input until it completes one full cycle and confirms the cell is behaving within expected parameters. Run a full charge at standard current first. On the next charge cycle, fast charging should negotiate normally.