TP-Link TL-TR961 Replacement Battery TBL-55A2550 3.8V

TP-Link TL-TR961 / M7350 — 3.8V Li-ion Replacement Battery (TBL-55A2550)

This 3.8V, 1900mAh Li-ion battery replaces the OEM TBL-55A2550 in the TP-Link TL-TR961 and M7350 mobile hotspot devices, including M7350 Ver 2. When the original cell degrades, the hotspot loses the ability to hold a charge through a full session. This replacement restores normal operation.

• TL-TR961, M7350, and M7350 Ver 2 compatibility: All three models share the same 3.8V power rail, physical form factor (68.48 × 48.55 × 5.60mm), and BMS communication protocol. One cell fits all three without modification.
• Bench tested on actual hardware: We ran this battery under simultaneous cellular modem and Wi-Fi radio load. The BMS maintained stable output voltage through connection spikes and handled charge termination cleanly at full capacity.
• Ventilation during extended hotspot sessions: Keep the TL-TR961 on an open surface — not in a bag or pocket — during long sessions. When connected devices are far from the hotspot, the cellular radio operates at full transmit power. Trapped heat around the battery accelerates cell degradation faster than normal cycling does.

Why the TL-TR961 drops connected devices mid-session under full load

The TL-TR961 runs two power-hungry radios simultaneously — the cellular modem and the Wi-Fi chipset. At maximum connected devices, combined draw can spike sharply and pull battery voltage below the BMS cutoff threshold momentarily. An aged or degraded cell has higher internal resistance, so voltage sags faster under that combined load than a fresh cell would. The hotspot interprets the voltage drop as a low-battery condition and shuts the radios down to protect the cell. A new cell with lower internal resistance holds voltage steady through those spikes and keeps connections alive.

TL-TR961 won't power on after sitting unused for weeks

Li-ion cells self-discharge during storage, and the TBL-55A2550 is no exception. If the hotspot sat unused long enough, the cell may have dropped below the minimum boot voltage — typically around 3.0V — and the BMS locks out discharge to prevent damage. Plugging it in and charging for at least 30 minutes before pressing power gives the BMS time to re-initialize and allow the device to boot. If the original cell won't recover after a full charge cycle, it has likely degraded beyond recovery and needs replacement.