Novatel Wireless MiFi 6620L Replacement Battery 3.8V 3600mAh

Novatel Wireless MiFi 6620L — 3.8V Li-ion Replacement Battery (40115131.01)

This 3.8V, 3600mAh Li-ion battery replaces the factory cell in the Novatel Wireless MiFi 6620L and Jetpack MiFi 6620L portable hotspot. It also fits the MiFi 6630 series. OEM part numbers covered: 40115131.01 and GB-S10-985354-0100.

• MiFi 6620L and 6630 series fit: Both devices share the same battery bay dimensions, connector pinout, and BMS communication protocol. The 3.8V nominal voltage rail and 58.85 × 53.00 × 9.95mm cell footprint are identical across the range, so one cell works across the full cluster.
• Bench tested on actual hardware: We ran this cell in a MiFi 6620L under a simulated five-device load with an active LTE connection. The BMS held voltage within spec throughout charge and discharge cycles, and the device firmware accepted the cell without a fault flag.
• Ventilation during extended sessions: Keep the hotspot on an open surface when running continuous sessions. When connected devices are far from the unit, the cellular radio pushes to maximum output power. That sustained RF draw concentrates heat at the cell — a blocked vent or pocket placement accelerates cell stress under that condition.

Why the MiFi 6620L drops all connected devices mid-session

The MiFi 6620L runs two high-draw subsystems simultaneously: the LTE modem and the WiFi radio. When the hotspot is serving the maximum number of clients and the cellular signal is weak, both radios operate at peak output at the same time. This combined current spike can pull the battery voltage below the BMS protection threshold, triggering an automatic shutdown to protect the cell. A worn original battery — with higher internal resistance — hits that cutoff voltage earlier under load than a fresh cell at full 3600mAh capacity.

MiFi 6620L won't power on after sitting unused for several weeks

Li-ion cells self-discharge at roughly 2–3% per month, but the MiFi 6620L's standby circuitry draws a small parasitic current even when the device is off. Over several weeks, that background drain can pull the cell below the minimum boot voltage — typically around 3.0V — and the device won't respond to the power button. Connect the hotspot to a charger and leave it for at least 30 minutes before attempting to power on. If the LED doesn't respond after 30 minutes of charging, the original cell has likely dropped below recoverable voltage and replacement is the only path forward.