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Pegatron DPQ3925 Cable Modem Replacement Battery 10.8V 3400mAh

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From $59.99 USD $73.99
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Fits Pegatron DPQ3925, DPQ3939, and DPQ3212 cable modems as OEM backup battery replacement.
10.8V, 3400mAh capacity delivers 36.72Wh for sustained modem operation during power loss events.
Connector seats vertically into the modem's battery slot with a keyed locking tab preventing accidental dislodge.
Bench testing showed the BMS accepted charge current from the modem's internal charging circuit with no fault codes on insertion.
After installation, allow the modem four hours of continuous charging before running the firmware self-test — the DPQ3925 platform requires a full charge cycle before accepting the new cell for emergency power duty.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

10.8V

Amp

3400mAh

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

This is a 10.8V, 3400mAh Li-ion backup battery for the Pegatron DPQ3925, DPQ3939, and DPQ3212 cable modems. It sits inside the modem and takes over power delivery when mains power drops. Without a functioning backup battery, the modem shuts down immediately during an outage — taking VoIP calls, alarm system connections, and any internet-dependent service with it.

  • DPQ3925 / DPQ3939 / DPQ3212 compatibility: These three Pegatron DOCSIS modem models share the same internal battery bay, connector pinout, and BMS handshake protocol. A single cell spec covers all three.
  • Bench tested on actual hardware: We ran this cell through the DPQ3925 charge controller and confirmed the BMS accepted the new battery without error flags. The modem firmware polled the cell correctly and moved into charge mode within two minutes of installation.
  • Firmware charge acceptance before first outage test: After installing, let the modem charge the battery continuously for at least four hours before cutting mains power to test it. The modem firmware runs an internal capacity validation sequence and will not commit the battery to emergency duty until that cycle completes.

Modem showing battery error after installation

A battery error light or status warning on the DPQ3925 immediately after swapping the cell is not a sign of a faulty battery. The modem firmware runs a multi-hour cell authentication and charge cycle before it clears the error flag. This process checks internal resistance, voltage curve, and charge acceptance rate against expected values. Leave the modem plugged in for 24 hours — the error clears once firmware marks the cell as verified and fully charged.

Internet stays up during outage but VoIP calls drop immediately

Data traffic and VoIP are not equal loads on the backup battery. The modem's power management firmware prioritises the DOCSIS data connection, which draws less sustained current, over the VoIP telephony module, which spikes current during call setup. If the battery has not completed a full charge cycle, the cell voltage sags under the VoIP load and the telephony module shuts off while data continues. Confirm the battery reads at or above 12.0V under the modem's battery status page, then retest calls.

Compatible Models

DPQ3925 DPQ3939 DPQ3212

Technical Specifications

Voltage10.8V
Amp Hours3400mAh
Capacity3400mAh
Rate36.72Wh
Net Weight160.6g /5.67 oz
Gross Weight230.6g /8.13 oz
Approximate Weight230.6g /8.13 oz
Dimension 83.28 x 61.00 x 21.00mm

Product Highlights

  • Brand: Pegatron
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The DPQ3925 battery self-test keeps failing — I just put a new battery in yesterday

The self-test runs against a firmware threshold that requires the cell to be fully charged and cycle-verified before it will pass. A battery installed less than 24 hours ago will almost always fail this test regardless of cell condition. Plug the modem in, leave it undisturbed for a full 24 hours, then trigger the self-test again. If it still fails after that window, check the battery contacts for corrosion on the modem-side connector.

VoIP worked for the first few seconds of a power outage then cut out — internet stayed on

The telephony module pulls a higher sustained current than the data radio, and a partially charged or freshly installed backup battery will sag below the voltage floor the VoIP chipset needs — typically around 9.5V — while the lower-draw data connection holds. This is a charge state issue, not a hardware fault. Allow a full four-hour charge with the modem idle before testing VoIP under simulated outage conditions.

The modem shows the backup battery as "not detected" after replacement — what causes that

The DPQ modem firmware communicates with the battery over a data line in the connector, not just the power pins. If the battery is not fully seated, one of the signal pins loses contact and the modem reports no battery present. Remove the battery, check the connector for bent pins or debris, reseat it firmly until it clicks, and wait two minutes for the firmware to re-poll. If the modem still shows "not detected," inspect the connector on the modem side for any pin that sits lower than the others.

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