ZEBAU1 SoftBank Pocket WiFi 303ZT Compatible Battery 3.7V 2500mAh

SoftBank Pocket WiFi 303ZT — 3.7V Li-Polymer Replacement Battery (ZEBAU1)

This 3.7V, 2500mAh Li-Polymer battery replaces the ZEBAU1 cell in the SoftBank Pocket WiFi 303ZT mobile hotspot. It fits directly into the 303ZT chassis and restores power to the device's combined LTE modem and Wi-Fi radio stack. Capacity figure is 2500mAh (9.25Wh) as rated for this unit.

• 303ZT platform fit: The 303ZT runs a single-cell Li-Polymer architecture at 3.7V nominal. The ZEBAU1 cell dimensions — 80.55 x 47.16 x 5.56mm — match the original battery bay exactly, and the BMS connector pinout is unchanged from the factory configuration.
• Bench tested on actual hardware: We cycled this cell under simultaneous modem and Wi-Fi load — five connected clients, active data transfer. The BMS held voltage within the expected operating window and did not trigger low-voltage cutoff during sustained draw.
• Ventilation during extended sessions: Keep the 303ZT on a flat, open surface when running multiple connected devices for long periods. The LTE radio ramps to maximum output power in poor signal conditions, and heat buildup in an enclosed space accelerates cell degradation faster than normal cycling would.

Hotspot disconnecting users mid-session on a new battery

The 303ZT draws current from two subsystems simultaneously — the cellular modem and the Wi-Fi radio. At maximum connected clients, this combined load can cause brief voltage sag on a partially discharged cell, which the BMS interprets as a low-voltage event and triggers a protection cutoff. The device reboots, dropping all connected sessions. To reduce sag events, keep the battery above 30% charge during heavy multi-device use and avoid running the hotspot while charging via USB — the charge path and discharge path share the same BMS, which can create current contention.

303ZT not powering on after sitting unused

Li-Polymer cells self-discharge over time, and if the 303ZT sits unused for several months, the battery can drop below the minimum boot voltage — typically under 3.0V for a 3.7V nominal cell. At that level, the BMS locks out discharge to protect the cell, and the device will not respond to the power button. Connect the hotspot to a charger and leave it for at least 30–60 minutes before attempting to power on — the charger bypasses the BMS lockout and trickle-charges the cell back above the recovery threshold. If the device shows a charging indicator after that window, the cell has recovered; target a full charge to 4.2V before use.