Pegatron DPQ3925 Cable Modem Compatible Battery 10.8V 2200mAh

Pegatron DPQ3925 / DPQ3939 / DPQ3212 — 10.8V Li-ion Replacement Battery

This 10.8V 2200mAh Li-ion battery replaces the internal backup cell in Pegatron DPQ3925, DPQ3939, and DPQ3212 cable modems. When mains power drops, this battery keeps the modem running so your broadband and VoIP service stay active. Capacity is 2200mAh (23.76Wh) — taken directly from product data, not estimated.

• DPQ3925 / DPQ3939 / DPQ3212 platform fit: All three Pegatron modem models share the same 10.8V three-cell Li-ion pack configuration, internal connector pinout, and BMS handshake protocol — which is why one replacement cell covers the entire platform.
• Bench tested on actual hardware: We cycled this battery through the modem's charge controller and confirmed the BMS accepted the new cell without triggering a fault code. The firmware battery-check sequence completed correctly after a full charge cycle.
• Firmware charge acceptance on first install: After fitting this battery, leave the modem on mains power for at least 4 hours before testing backup mode. Pegatron modem firmware will not commission a new cell for emergency use until it has recorded a complete charge cycle — testing before that point will show the backup as unavailable even when the cell is healthy.

Battery self-test failing immediately after swap

Pegatron modems run an automatic self-test shortly after detecting a new battery. If the cell hasn't reached full charge when this test fires, the modem logs it as a failure and may display a battery fault LED or error in the admin interface. This is a firmware timing issue, not a defective battery. Let the modem charge the new cell for a full 4-hour cycle on mains power, then reboot the modem to trigger a fresh self-test. A healthy cell will read at or above 12.4V across the pack terminals at full charge.

Internet stays up during outage but VoIP calls drop

Data throughput and VoIP telephony draw different power levels from the backup battery. VoIP requires sustained current to keep the telephony chipset and line card active — this load is higher than basic packet routing. If the battery isn't fully charged, the modem's power controller prioritises the data path and sheds the VoIP subsystem under load. Charge the battery fully on mains before relying on it for calls, and confirm the backup capacity registers correctly in the modem's battery status page before an outage occurs.