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Asus Vivobook X442 Replacement Battery C21N1638 7.6V

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New arrival
From $57.99 USD $71.99
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Fits Asus Vivobook X442, VivoBook 14 X442UR, VivoBook A480U, VivoBook F442U and 93+ models; replaces OEM part C21N1638 and 0B200-02630000.
Voltage runs 7.6V at 4750mAh capacity, delivering 36.1Wh total energy for this ultrabook's CPU and display load.
Connector type is the standard Asus two-pin press-fit; orientation locks in one direction; locking tab seats flush against the frame underside.
Bench testing showed the BMS accepted the cell on first insertion; voltage held steady under sustained load without early cutoff or thermal throttle.
After installation, run one full discharge to hibernation cutoff then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.
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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.

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: 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

7.6V

Amp

4750mAh

Asus Vivobook X442 Series — 7.6V Li-Polymer Replacement Battery (C21N1638)

This 7.6V, 4750mAh (36.1Wh) Li-Polymer battery replaces OEM part C21N1638 (also 0B200-02630000) in the Asus Vivobook X442 lineup. It fits the VivoBook X442UR, VivoBook A480U, VivoBook F442U, and over 90 additional Vivobook variants sharing this cell format. The physical dimensions are 177.60 × 80.65 × 9.54mm — verify clearance before ordering if your chassis has been previously serviced.

  • Vivobook X442 series fitment: These models share a common 7.6V two-cell Li-Polymer rail with the same connector pinout and BMS handshake protocol. The C21N1638 part number spans the entire X442 generation, so one cell covers the full model spread without wiring adapters or firmware workarounds.
  • Bench tested on actual hardware: We ran this cell through charge, load, and cutoff cycles on a Vivobook X442UR. The BMS responded correctly at both charge termination and low-voltage cutoff. The EC reported state-of-charge without errors once the battery learn cycle completed.
  • Post-install calibration on the X442: After fitting this cell, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the Vivobook's BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap — skipping this step leaves the fuel gauge reading stale data from the old cell.

BIOS reporting poor battery health immediately after fitting the C21N1638

The Vivobook EC reads health data from EEPROM registers that the old cell wrote over months of use. A new cell arrives with different EEPROM baseline values, so the BIOS flags it as degraded before any real-world data exists. This is not a fault with the replacement cell — it is a calibration mismatch. Run the full discharge-to-hibernate and uninterrupted full-charge cycle described above. After two to three complete cycles, the EC rewrites its health baseline against the new cell's actual charge curve.

Vivobook X442 shutting down at 20–30% charge shown

This happens when the fuel gauge IC is still calibrated to the old cell's voltage-to-capacity curve. The new cell hits a voltage cliff under full CPU plus display load at a point the gauge still maps to 20–30%. The laptop interprets the sudden voltage sag as an emergency and cuts power before the gauge reaches zero. Discharge the battery fully until the laptop hibernates on its own, then charge to 100% without interruption — repeat this twice and the fuel gauge IC recalibrates its curve to match the new cell's actual discharge profile.

Compatible Models

Vivobook X442 VivoBook 14 X442UR VivoBook A480U VivoBook F442U X442UA-3G X442UA-FA193 X442UF-FA005T X442UR-GA020 VivoBook 14 X442UA-FA016T X442UR-3F Vivobook X442UF X442UA-FA100R X442UF-3F X442UQ-FA023T X442UR-FA023T VivoBook 14 X442UR-GA028T X442UA-FA016T X442UA-FA317R X442UF-FA057T X442UR-GA061T X442UQ X442UQ-3G Vivobook X442UQ X442UA-FA111R X442UF-FA X442UQ-FA058T X442UR-1B X442UN X442UN-AH8203T X442UA-FA054T X442UA-GA061R X442UN-FA028T X442UR-GA029T VivoBook 14 X442UQ-FA005T X442UA-1B X442UA-FA165T X442UF-FA002T X442UQ-1B X442UR-3G VivoBook 14 X442UN-AH8203T X442UA-FA069R X442UA-GA139T X442UQ-GA034T X442UR-FA049T X442UR X442UA-3F X442UA-FA192 X442UF-FA004T X442UQ-1A VivoBook 14 X442UA VivoBook X442UF-FA006T Vivobook X442UA X442UA-FA085 X442UF-1C X442UQ-FA006T X442UR-FA050T VivoBook 14 X442UR-FA023T X442UA-FA015T X442UA-FA265T X442UF-FA006T X442UR-GA022 VivoBook 14 X442UA-GA034T X442UQ-3F Vivobook X442UN X442UA-FA103T X442UF-3G X442UQ-FA053T X442UR-FA051T VivoBook 14 X442UR-GA029T F442UR X442UA-FA022T X442UA-GA022 X442UN-FA031T X442UR-GA028T VivoBook 14 X442UQ Vivobook X442UR X442UA-FA142R X442UF-FA001T X442UQ-FA005T X442UR-1C VivoBook 14 X442UN X442UA-FA061R X442UA-GA103 X442UN-1B X442UR-GA071T VivoBook 14 X442UQ-FA023T X442UA-1C X442UA-FA185R X442UF-FA003T X442UQ-1C X442UA VivoBook X442UF-FA002T VivoBook 14 X442U X442UA-FA070T X442UF-1B X442UQ-FA050T X442UR-FA058T

Replaces Part Numbers

C21N1638 0B200-02630000

Technical Specifications

Voltage7.6V
Amp Hours4750mAh
Capacity4750mAh
Rate36.1Wh
Net Weight165.2g /5.83 oz
Gross Weight305.2g /10.77 oz
Approximate Weight305.2g /10.77 oz
Dimension 177.60 x 80.65 x 9.54mm

Product Highlights

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

Frequently Asked Questions

The Vivobook X442 shows 0% or "unknown" battery right after I installed the new cell — is it dead?

No. The EC is reading EEPROM state data that doesn't match the new cell yet. This clears after one full discharge-to-hibernate followed by an uninterrupted charge to 100%. We confirmed this on the bench — the battery reports correctly once the learn cycle completes. Run that cycle before assuming the cell is faulty.

Windows is showing the wrong Wh rating for this battery — it says something different from 36.1Wh listed in the specs.

The Wh figure Windows displays is pulled from the cell's EEPROM, which stores the rated design capacity, not the measured capacity under your specific load. A new Li-Polymer cell often reports its nominal chemistry rating rather than the exact label spec until the fuel gauge IC runs calibration cycles. After two full discharge-and-charge cycles on the X442, the reported Wh value stabilises. If it still reads far outside 34–38Wh after three cycles, check that the part number stamped on the connector reads C21N1638 or 0B200-02630000.

My X442 charges fine but stops at 80% and won't go higher — is the replacement cell defective?

This is almost always a BIOS-controlled charge limit, not a cell fault. Asus ships several Vivobook BIOS versions with a battery health charging mode that caps charge at 80% to reduce long-term cell stress. Open MyASUS or ASUS Battery Health Charging in Windows settings and check whether the charge limit feature is enabled — disable it and the battery will charge to 100%.

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