About this replacement
Archos 40 Helium — 3.7V Li-ion Replacement Battery (AC40HE)
This 3.7V, 1500mAh Li-ion cell replaces the original AC40HE battery in the Archos 40 Helium smartphone. It restores power to calling, messaging, and app functions when the original cell has degraded or failed to hold a charge. Dimensions are 75.90 × 49.85 × 4.00mm — match these before fitting.
- Archos 40 Helium fit: The 40 Helium uses a fixed 3.7V cell with the AC40HE part number. The connector pinout and physical envelope are specific to this model — no other Archos 40-series variant shares this exact cell profile.
- Bench tested on actual hardware: We ran the cell through full charge and discharge cycles on the bench. The BMS held voltage within spec at load and triggered protection cutoff correctly at low-cell threshold — no unexpected trips during modem simulation.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging is applied to an uncalibrated cell.
Sudden shutdown at 20–30% on the Archos 40 Helium after a cell swap
The 40 Helium's modem and display draw sharp current spikes. A new cell with a slightly different internal resistance curve can cause voltage to sag below the BMS cutoff threshold under that load — even when the fuel gauge still reads 20–30%. The phone's coulomb counter is still calibrated to the old cell's discharge profile, so the percentage shown does not reflect the new cell's actual remaining capacity. Running one full discharge cycle from 100% to automatic shutdown, then charging uninterrupted to 100%, lets the gauge IC remap to the new curve. After that cycle, shutdown events at false-high percentages typically stop.
Device will not power on after the replacement battery sat in storage
Li-ion cells self-discharge in storage. If this cell arrived or was stored below 2.5V, the BMS may have entered lockout to prevent damage — the phone will show no response to the power button and no charge indicator. Connect the phone to a wall charger rated at 5V/1A and leave it for 20–30 minutes without pressing anything. The charge IC will trickle current into the cell to bring it above the BMS re-enable threshold, typically around 2.9–3.0V, after which normal charging resumes and the phone will power on.