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Asus BU201 Replacement Battery 7.6V 4200mAh B21N1404

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From $67.99 USD $82.99
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Replaces Asus B21N1404 battery in BU201, BU201L, BU201LA ultrabook models.
7.6V 4200mAh (31.92Wh) capacity restores full charge retention on the Asus BU201 platform.
Connector slides into the underside slot with a single locking tab; orientation marked on board.
We bench-tested this cell in a BU201LA — BMS accepted the new pack on first insertion without fault codes.
After installation, discharge fully to sleep mode then charge uninterrupted to 100% to reset the BIOS fuel gauge calibration cycle.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
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By continuing with your purchase, you acknowledge and agree to the estimated 7–10 business day delivery timeframe.
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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.

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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

7.6V

Amp

4200mAh

Asus BU201 Series — 7.6V Li-ion Replacement Battery (B21N1404)

This 7.6V 4200mAh (31.92Wh) Li-ion battery replaces the OEM B21N1404 cell in the Asus BU201, BU201L, BU201LA, and Pro Advanced BU201 ultrabooks. It fits the original bay without modification and uses the same connector pinout as the factory unit. Capacity figures are from the product specification — not extrapolated from web sources.

  • BU201 series compatibility: The BU201, BU201L, and BU201LA share an identical battery bay, connector, and BMS handshake protocol — all three draw from the same 7.6V cell platform, which is why a single OEM part number covers the full lineup.
  • Bench tested on actual hardware: We ran the B21N1404 replacement through charge and discharge cycles on a BU201LA unit. The BMS accepted charge from cold without tripping, and the BIOS recognised the cell as a valid pack on first boot.
  • Post-install calibration on the BU201: After fitting this battery, run one full discharge to hibernate-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 on this platform.

BIOS reporting poor battery health immediately after swap on the BU201

The BU201 BIOS reads EEPROM data stored in the battery pack to assess health. When a new cell arrives, that EEPROM carries factory baseline figures that the BIOS compares against its own learned cycle history — a mismatch triggers the health warning. This is not a fault with the replacement cell. Running one full discharge-to-hibernate followed by an uninterrupted full charge forces the BIOS to write a fresh learn cycle to the new pack's EEPROM and clears the warning on the next reboot.

BU201 shutting down at 20–30% charge shown on the gauge

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The gauge under-reports remaining capacity, so the BIOS triggers a low-battery shutdown before the cell is genuinely depleted. Two to three full discharge-and-charge cycles give the fuel gauge IC enough data to map the new cell accurately. After calibration, the shutdown threshold should align with a cell voltage at or below 6.8V under load.

Compatible Models

BU201 BU201L BU201LA Pro Advanced BU201 Pro Advanced BU201L Pro Advanced BU201LA

Replaces Part Numbers

B21N1404

Technical Specifications

Voltage7.6V
Amp Hours4200mAh
Capacity4200mAh
Rate31.92Wh
Net Weight187g /6.60 oz
Gross Weight327g /11.53 oz
Approximate Weight327g /11.53 oz
Dimension 189.45 x 87.90 x 12.00 mm

Product Highlights

  • Brand: Asus
  • 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

My BU201 shows 0% or "unknown" battery in Windows right after fitting the new cell — is the battery faulty?

It is not a fault with the replacement cell. The fuel gauge IC in the BU201 has lost its calibration reference when the old cell was removed, so it reports 0% or unknown until it re-establishes a baseline. Run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. After one or two cycles the OS gauge will read correctly.

The BU201 BIOS is reporting the Wh rating as lower than the 31.92Wh listed in the battery specs — why?

The BIOS reads the Wh figure from the battery pack's EEPROM, which stores the factory-rated value for the original cell chemistry. A replacement cell from a different production batch can carry a slightly different EEPROM value even at the same nominal capacity, producing a mismatch in system info. This is a data reporting difference, not a capacity reduction. The actual delivered capacity will align with the 4200mAh specification after the BIOS completes a full learn cycle.

Charge on the BU201 stops at 80% and will not go higher — is there a fault with the new battery?

The BU201 BIOS includes a firmware-controlled charge limit that caps charging at 80% when battery care mode is active. This is not a battery fault. Open Asus Battery Health Charging from the MyASUS app or Windows search, set it to Full Capacity Mode, then restart and begin a fresh charge cycle to 100%.

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