About this replacement
Sierra Wireless AirCard 875U / 880U Series — 3.2V Li-ion Replacement Battery (1201324)
This is a 3.2V, 380mAh Li-ion replacement battery for the Sierra Wireless AirCard 875U, 595U, 880U, and 881 mobile hotspot devices. It slots into the same bay as the original cell and restores portable operation when the factory battery has degraded. Capacity figure is 380mAh — use that number when comparing against your current cell's label.
- AirCard 875U / 595U / 880U / 881 compatibility: These AirCard models share the same 3.2V cell format and connector pinout, which is why a single part number — 1201324 — covers the full range. The BMS handshake voltage and charge termination point are identical across the group.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an AirCard 880U. The BMS engaged correctly at both the low-voltage cutoff and the charge termination threshold, with no false protection trips under combined cellular modem and Wi-Fi radio load.
- Signal environment matters for this cell: When your hotspot is operating in a weak signal area, the cellular radio pushes to maximum transmit power. That draw is significantly higher than in good-signal conditions and accelerates heat buildup in a small enclosure. Keep the device in an open, ventilated spot — not a pocket or bag — during extended sessions in low-signal zones.
Why the AirCard 875U drops Wi-Fi clients mid-session on a new battery
At maximum client connections, the AirCard runs both the cellular modem and the Wi-Fi radio at full power simultaneously. This combined draw can pull the cell voltage down faster than the BMS anticipates on a cold or partially conditioned battery. When voltage sags below the BMS trip threshold — typically around 2.7V under load — the device cuts power to protect the cell, dropping all connected clients instantly. Running two to three charge-discharge cycles before using the hotspot under full load allows the BMS to calibrate its internal state-of-charge model and reduces the likelihood of a premature trip.
AirCard won't power on after sitting unused for several weeks
A 380mAh Li-ion cell at this voltage tier self-discharges at roughly 2–3% per month under normal storage conditions, but internal leakage currents in the hotspot's standby circuitry can drain the cell faster than that. If the cell drops below approximately 2.5V, the BMS locks out power delivery entirely and the device shows no response to the power button. To recover, connect the hotspot to a USB power source and leave it on charge for at least 20–30 minutes before attempting to boot — the charger's pre-charge current brings the cell back above the BMS unlock threshold, after which normal charging resumes.