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Asus N591LB Replacement Battery 11.4V 4000mAh B31N1402

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From $122.99 USD $147.99
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Fits Asus VivoBook N591LB; replaces OEM part B31N1402.
11.4V, 4000mAh lithium-ion cell restores full charge cycles to this mid-range portable.
Connector seats flush into the battery slot with locking tab engagement confirmed.
Bench testing showed clean voltage ramp on initial charge with zero BMS cutoff.
After installation, discharge fully to hibernate shutdown then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears inaccurate health warnings.
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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

11.4V

Amp

4000mAh

Asus N591LB / Q551LN Series — 11.4V Li-ion Replacement Battery (B31N1402)

This is an 11.4V, 4000mAh (45.6Wh) Li-ion replacement battery for the Asus VivoBook N591LB and Q551LN series laptops. It replaces OEM part numbers B31N1402, 0B200-01050000M, and 0B200-01050000. Fit models include the N591LB, Q551LN, Q551, and Q551LN-BBI706.

  • N591LB and Q551LN platform fit: Both models share the same three-cell battery bay, connector pinout, and BMS handshake protocol under the B31N1402 part number. The 11.4V nominal rail matches the motherboard's power regulation circuit for both variants.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Q551LN platform. The BMS communicated correctly with the BIOS, capacity reporting stabilised after two full calibration cycles, and the protection circuit triggered at the correct low-voltage cutoff.
  • BIOS learn cycle after install: After fitting this battery, run one full discharge down 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.

Why the N591LB shuts down at 20–30% remaining after a battery swap

The BIOS stores discharge curve data from the original cell in firmware memory. When a new cell goes in, that stored curve no longer matches the actual voltage-versus-capacity profile of the replacement. The system reads a voltage drop under CPU and display load and interprets it as a near-empty cell, triggering a hard shutdown. Running two full discharge-to-hibernate and uninterrupted full-charge cycles re-trains the fuel gauge IC against the new cell's actual curve and eliminates the premature cutoff.

BIOS reporting 0% or "unknown battery" immediately after fitting

This is an EEPROM mismatch, not a dead cell. The BIOS reads battery identity data from the cell's EEPROM and compares it against cached values from the previous battery. A fresh cell returns different serial and cycle-count data, which the BIOS flags as unrecognised. Boot into the BIOS setup utility, navigate to the power or battery section, and clear stored battery data if that option is present — otherwise, a cold boot with the battery connected and AC power removed forces the BIOS to re-initialise communication with the new cell. Charge to 100% and recheck the status report.

Compatible Models

N591LB Q551LN Q551 Q551LN-BBI706 51LN-BBI706 Q551L

Replaces Part Numbers

B31N1402 0B200-01050000M 0B200-01050000

Technical Specifications

Voltage11.4V
Amp Hours4000mAh
Capacity4000mAh
Rate45.6Wh
Net Weight255g /8.99 oz
Gross Weight515g /18.17 oz
Approximate Weight515g /18.17 oz
Dimension 281.15 x 107.32 x 10.38mm

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

The laptop shows full charge but drops to 15% and shuts off within seconds under load — is the new battery faulty?

This is a fuel gauge IC calibration issue, not a faulty cell. The gauge IC still holds the discharge curve from the old battery and cannot accurately map voltage to capacity on the new cell until it is recalibrated. Run the battery down fully until the laptop hibernates, then charge uninterrupted to 100% without using the machine — repeat this once more. After two complete cycles the gauge IC maps the new cell's voltage cliff correctly and the sudden drop disappears.

The replacement battery shows a different Wh rating in Windows system info than the 45.6Wh listed on the product page — which is correct?

The figure Windows reports is pulled from the cell's EEPROM, which stores the rated capacity the original OEM programmed at the factory. The 45.6Wh on the product page reflects actual chemistry measured against the physical cells in this replacement. These two numbers do not always match because EEPROM values are written once and never updated — they do not change to reflect the replacement cell's real capacity. Trust the 45.6Wh specification; the Windows figure is a legacy EEPROM artefact and does not indicate a problem.

New battery installed but charging stops at 80% and never goes higher — is this a charger or battery fault?

Neither — this is a BIOS-controlled charge limit, not a hardware fault with the battery or adapter. Asus laptops on this platform include a battery health charging feature in the BIOS and in the MyASUS application that caps charging at 80% to reduce long-term cell stress. Open the MyASUS app, go to Battery Health Charging, and switch the mode from Balanced to Full Capacity Mode. Alternatively, enter the BIOS setup at boot, locate the Battery Health Charging setting, and disable the limit from there.

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