NTT DoCoMo L09C Replacement Battery 3.7V 2400mAh Li-ion

NTT DoCoMo L09C / L13 — 3.7V Li-ion Replacement Battery (L13, EAC61579101)

This 3.7V 2400mAh Li-ion battery fits the NTT DoCoMo L09C and L13 pocket mobile hotspot routers, along with the AGL29141 variant. It replaces OEM part numbers L13 and EAC61579101 directly. If your hotspot is shutting down mid-session or no longer holding a charge, this is the cell that needs swapping.

• L09C, L13, and AGL29141 compatibility: All three models share the same 3.7V cell footprint, connector pinout, and BMS handshake protocol. The onboard charging circuit recognises this battery without recalibration or error flags.
• Bench tested on actual hardware: We cycled this battery on the L09C with five concurrent connected clients and active LTE data transfer. The BMS held stable across charge and discharge cycles with no false low-voltage cutoffs.
• Ventilation during extended hotspot sessions: Keep the L09C on a hard, open surface during extended use. When the device is far from connected clients or in a weak signal area, the cellular radio pushes maximum transmit power — heat builds fast in enclosed spaces and accelerates cell wear.

Why the L09C drops all connected clients mid-session on a new battery

The L09C runs two power-hungry subsystems simultaneously — the LTE modem and the 2.4GHz Wi-Fi radio. When multiple clients are active and the LTE signal is marginal, combined current draw spikes sharply. A degraded or undercharged cell cannot sustain the voltage rail through these peaks, so the BMS trips a protection cutoff and the device resets. This is not a firmware fault. Charge the battery to full before the first session, then check that nothing is blocking the device's ventilation slots.

L09C won't power on after sitting unused for several weeks

Li-ion cells self-discharge at roughly 2–3% per month under normal conditions, but the L09C's standby circuit draws a small parasitic load even when powered off. After extended storage, the cell can drop below the 3.0V threshold the BMS requires to allow a boot sequence. Plug the hotspot into its charger and leave it connected for at least 30 minutes before attempting to power on — this gives the BMS enough voltage headroom to re-initialise. If the charging LED does not light within five minutes, the cell has likely dropped below 2.5V and recovery may require a slow pre-charge cycle using a compatible external Li-ion charger set to 0.1C.