FOXLINK FLK644A Cable Modem Replacement Battery 10.8V 3400mAh
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FOXLINK FLK644A Cable Modem Replacement Battery 10.8V 3400mAh - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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.
Delivery and Shipping
Delivery and Shipping
🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.
Disclaimer
Disclaimer
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🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.
FOXLINK FLK644A Cable Modem Replacement Battery 10.8V 3400mAh - is backordered and will ship as soon as it is back in stock.
Voltage
10.8V
Amp
3400mAh
FOXLINK FLK644A — 10.8V Li-ion Replacement Battery
This is a 10.8V, 3400mAh Li-ion replacement battery for the FOXLINK FLK644A cable modem backup unit. It restores the modem's ability to stay powered during outages, keeping your internet connection and VoIP line active when mains power drops. Capacity is 36.72Wh, matching the original cell specification.
- Cable modem backup platform: Cable modems in the CPB013RX category share a 10.8V three-cell battery architecture with a common connector and BMS handshake that the modem firmware polls on boot. Any voltage mismatch or failed handshake causes the modem to reject the battery outright rather than charge it.
- Bench tested on actual hardware: We ran this cell through the modem's BMS handshake sequence and confirmed the firmware acknowledged the battery within the first boot cycle. The protection circuit responded correctly to both charge and discharge thresholds without triggering a fault code.
- First-charge requirement after installation: Cable modem firmware will not activate backup power until the battery reports a full charge state. Connect the modem to mains power and allow at least four hours of uninterrupted charging before testing backup function — cutting this short means the modem treats the battery as unavailable.
Modem showing battery error after installation
When a new cell is installed, the modem firmware runs a battery acceptance sequence that can take up to 24 hours. During that window, the modem may display a battery fault LED or error code even though the battery is physically connected and charging correctly. This is a firmware timing behaviour, not a defective cell. Leave the modem on mains power and the error will clear once the firmware completes its validation cycle.
VoIP calls dropping during power outage while internet stays up
Data throughput and VoIP telephony draw different sustained power loads from the backup battery. During an outage, the modem allocates battery output to maintain the DOCSIS data channel first — VoIP requires a higher, sustained current draw that a partially charged or degraded cell cannot support. If calls drop but browsing continues, the battery has not completed a full charge cycle. Charge to 100% on mains power, confirm the battery LED is solid, then retest VoIP during a simulated outage.
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: FOXLINK
- 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 modem shows a battery fault light right after I installed the new FOXLINK FLK644A — is it dead?
No — this is normal firmware behaviour. The modem runs an internal battery acceptance sequence after any new cell is installed, and it reports a fault during that process. Leave the modem connected to mains power for up to 24 hours. The fault indicator will clear once the firmware completes its validation cycle and the cell reaches a full charge state.
My modem passed the battery self-test yesterday, but it's failing again today — what's happening?
A self-test failure the day after a pass usually means the battery hasn't completed a full conditioning charge. Cable modem firmware triggers a self-test on a schedule, and if the cell voltage hasn't stabilised above the minimum threshold — typically 12.0V fully charged on a 10.8V nominal cell — the test will fail. Keep the modem on mains power for a full four-hour charge before running or scheduling any self-test. If the failure persists after that, check that the battery connector is fully seated.
Internet stays on during a power cut, but my phone line goes dead — why doesn't the backup battery keep VoIP working?
VoIP requires a higher sustained current draw than maintaining the data channel alone. If the battery is only partially charged, the modem prioritises the DOCSIS connection and the VoIP module loses power first. Allow the battery a full four-hour charge on mains power after installation, confirm the battery status LED is solid green, then simulate an outage by unplugging the mains and verify the phone line stays active.
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