Sierra Wireless Overdrive 4G W-1 Compatible Battery 3.7V 1800mAh

Sierra Wireless Overdrive 4G Series — 3.7V Li-ion Replacement Battery (W-1 / BATW801)

This 3.7V 1800mAh Li-ion battery fits the Sierra Wireless Overdrive 4G and Overdrive 4G+ mobile hotspot devices, along with the Aircard 753S and compatible variants. It replaces OEM part numbers W-1, 1201883, and BATW801. The Overdrive creates a shared 4G LTE connection for multiple Wi-Fi clients — the battery carries the combined load of the cellular modem and the Wi-Fi radio simultaneously.

• Overdrive 4G and 4G+ compatibility: Both devices run on the same 3.7V single-cell Li-ion platform with the same connector and BMS handshake. The W-1 part number spans both models, so one replacement covers the full Overdrive family in this series.
• Bench tested on actual hardware: We ran this battery under combined modem and Wi-Fi radio load, simulating multiple connected clients. The BMS held voltage stable across the draw cycle and did not trigger a low-voltage cutoff under normal operating conditions.
• Signal environment tip: In poor cellular coverage areas, the modem ramps to full transmit power. Position the Overdrive near a window or elevated surface to improve signal — this reduces transmit power demand and lowers thermal stress on the battery during long sessions.

Why the Overdrive 4G drops all connected clients mid-session on a new battery

When multiple clients are active at maximum range, the Wi-Fi radio and cellular modem both pull peak current at the same time. This combined spike can sag battery voltage below the BMS protection threshold momentarily, triggering a shutdown even when the battery shows adequate charge. The Overdrive's BMS is conservative — it cuts output quickly to protect the cell. If drop-outs happen at five or more connected clients, reduce the client count or move the hotspot closer to the router or tower to lower simultaneous peak draw.

Overdrive 4G won't power on after sitting unused for several weeks

Li-ion cells self-discharge during storage. If the Overdrive sat for more than three to four weeks without charging, the cell voltage may have fallen below 3.0V — the minimum threshold the BMS requires to allow boot. At that point, the device shows no response to the power button. Connect it to the OEM charger and leave it for at least 30 minutes before attempting to power on; the BMS needs to detect a recovery charge above 3.0V before it re-enables the output rail.