ARRIS NVG589 Replacement Battery 7.4V 5600mAh Li-ion

ARRIS NVG589 / NVG599 — 7.4V Li-ion Replacement Battery (586185-001-00)

This is a 7.4V 5600mAh lithium-ion battery for the ARRIS NVG589 and NVG599 VDSL2 gateways. It slots into the battery bay on the underside of the modem and provides backup power when mains electricity cuts out. Fits both the NVG589 and NVG599 under OEM part numbers 586185-001-00 and 586185-002-00.

• NVG589 and NVG599 shared battery platform: Both gateways use the same battery bay geometry, voltage rail, and BMS handshake protocol, which is why they share a single OEM part number family. The modem firmware polls the battery over a dedicated sense line — the cell chemistry and connector pinout must match exactly or the modem will flag a fault.
• Bench tested on actual hardware: We ran this cell in an NVG589 and confirmed the BMS handshake completed without fault codes. The modem accepted the battery, initiated its charge cycle, and cleared the battery LED indicator within the expected window.
• First charge cycle on the NVG589: After installation, leave the modem plugged into mains power for at least four hours before testing backup mode. The NVG589 firmware will not commit the battery to emergency power duty until it has completed one full supervised charge cycle — skipping this step causes the backup function to fail silently.

Battery self-test failing immediately after swap on the NVG589

The NVG589 runs an automated self-test shortly after boot and again on a rolling schedule. A freshly installed battery will almost always fail this test if it hasn't completed a full charge cycle first. The modem's firmware interprets a low state-of-charge as a failed cell, not an uncharged one. Allow four hours of continuous mains power before triggering or observing any self-test result — at that point the battery voltage should sit at or above 8.0V under no-load conditions.

Modem holds internet during outage but VoIP calls drop

Data-only traffic draws roughly half the sustained current that active VoIP sessions require. If the battery is partially charged or the cells have a high internal resistance, the modem can maintain a DOCSIS data link but cannot sustain the power spike when the ATA subsystem engages for a voice call. Check that the battery has completed its initial charge cycle and that the battery LED on the modem is solid green, not amber. If VoIP still drops under backup power, measure battery voltage under load — anything below 7.0V mid-call points to a weak cell that needs replacement.