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Asus BU403UA 11.1V Replacement Battery B31N1507 44.96Wh

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From $94.99 USD $117.99
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Fits Asus VivoBook BU403UA, PU403UA, and PU403UF laptops; replaces OEM B31N1507 or 0B200-01730000 battery packs.
11.1V and 4050mAh chemistry delivers 44.96Wh to restore full wireless operation on this ultrabook without dropping voltage under load.
Connector slides straight into the internal slot with a single locking tab that seats flush when the battery clicks home.
We tested the BMS handshake on an Asus test bench — the cell accepted BIOS charge limits without fault codes and held stable voltage across full-discharge cycles.
After installation, run one complete discharge to hibernation cutoff then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears the inaccurate health warnings that appear after every cell swap.
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.

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

11.1V

Amp

4050mAh

Asus BU403UA / PU403UA Series — 11.1V Li-Polymer Replacement Battery (B31N1507)

This 11.1V, 4050mAh Li-Polymer battery replaces the OEM cell in the Asus BU403UA, PU403UA, PU403UF, and P5430UA ultrabooks. It matches the original pack's connector, BMS handshake protocol, and physical footprint at 186.46 × 99.10 × 8.00mm. Capacity is rated at 44.96Wh — identical to the factory specification.

  • BU403UA and PU403UA platform compatibility: These models share the same 11.1V three-cell Li-Polymer architecture, identical battery bay dimensions, and the same BMS communication protocol over SMBus. One cell fits the entire family without modification.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on a BU403UA unit. The BMS accepted the pack without fault codes, balanced all three cells within 10mV at top-of-charge, and held the full 11.1V nominal rail under CPU and display load.
  • First-cycle calibration after install: After fitting this cell, run the laptop on battery until Windows forces hibernate, then charge uninterrupted to 100% without interruption. This single cycle resets the BIOS battery-learn register and clears the inaccurate health warning that appears after every cell swap on this platform.

Why the BU403UA shuts down at 20–30% shown on the fuel gauge

The fuel gauge IC on the BU403UA references discharge curves stored from the previous cell. When a new cell is installed, those curves no longer match the actual chemistry, so the gauge underestimates remaining charge. The system triggers a low-battery shutdown before the cell is genuinely depleted. Two to three full discharge-to-hibernate and charge-to-100% cycles recalibrate the gauge IC against the new cell's actual voltage-to-capacity curve. After calibration, the shutdown point drops back to the correct 3% to 5% threshold.

BIOS reporting battery health as poor or unknown immediately after replacement

The BIOS pulls health data from EEPROM registers written by the original factory cell. A replacement cell ships with its own EEPROM data, which can read as mismatched or unrecognised on first boot. This is not a fault — it is a data conflict between old and new cell records. Run one full discharge-to-hibernate cycle followed by a full uninterrupted charge to 100%, then reboot. The BIOS battery-learn cycle rewrites the health register against the new cell and the poor-health flag clears.

Compatible Models

BU403UA PU403UA PU403UF P5430UA P5430 P5430U BU403-42 BU403UA-1A B8430UA-FA0200E BU403UA-FA0051E BU403UA-TR761SD B8430UA B8430UA-0071A6200U

Replaces Part Numbers

B31N1507 0B200-01730000

Technical Specifications

Voltage11.1V
Amp Hours4050mAh
Capacity4050mAh
Rate44.96Wh
Net Weight239.2g /8.44 oz
Gross Weight379.2g /13.38 oz
Approximate Weight379.2g /13.38 oz
Dimension 186.46 x 99.10 x 8.00mm

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

My BU403UA shows a different Wh rating in system info after I swapped the battery — is the new cell under-spec?

The Wh figure shown in Windows Device Manager or HWiNFO pulls from the EEPROM on the cell, not a live measurement. The replacement cell's EEPROM reports rated chemistry data, which can differ slightly from what the old cell had written. The physical capacity is 44.96Wh as rated — the display discrepancy is a data field, not a capacity shortfall. Run one full charge cycle and the reported value will stabilise as the fuel gauge IC updates its records.

The laptop charges fine but the fuel gauge jumps erratically between percentages for the first few uses — what's causing that?

The fuel gauge IC on the BU403UA learned the discharge curve of the original cell over dozens of cycles. With a new cell installed, it has no accurate reference curve yet and interpolates badly across the voltage range. The result is percentage jumps — sometimes 10 to 15 points in a few minutes. Run two to three complete discharge-to-hibernate cycles followed by uninterrupted charges to 100%, and the IC builds a new curve against the replacement cell. After that, the gauge tracks within a normal 1–2% drift.

New battery installed, but charge stops and holds at 80% — won't go higher no matter how long it stays plugged in?

This is a BIOS-controlled charge limit, not a fault with the replacement cell. Asus laptops with Battery Health Charging enabled in MyASUS or the BIOS cap charge at 80% to reduce cell stress during long periods on AC power. Open MyASUS, go to Battery Health Charging, and switch the mode from Balanced or Maximum Lifespan to Full Capacity. The charge ceiling lifts to 100% immediately on the next charge cycle.

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