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Asus Zenbook UX305UA Replacement Battery 11.55V 4850mAh

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From $124.99 USD $149.99
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Fits Asus Zenbook UX305UA and UX305UAB models; replaces OEM part C31N1539.
11.55V 4850mAh lithium-polymer cell delivers 56.02Wh for full charge cycles on this ultrabook.
Connector seats flat against the motherboard with a single locking tab on the right side.
We bench-tested this cell in a UX305UA chassis; BMS accepted the new pack on first insertion without fault codes.
After installation, discharge the battery fully to system shutdown, then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears inaccurate health warnings common after every cell swap on this model.
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

11.55V

Amp

4850mAh

Asus Zenbook UX305UA — 11.55V Li-Polymer Replacement Battery (C31N1539)

This is a 11.55V, 4850mAh (56.02Wh) Li-Polymer replacement battery for the Asus Zenbook UX305UA and UX305UAB ultrabooks. It uses OEM part numbers C31N1539 and 0B200-01180200. Install it when the original cell no longer holds a charge or the system reports degraded battery health.

  • UX305UA and UX305UAB compatibility: Both variants share the same motherboard battery connector, voltage rail, and BMS handshake protocol, which is why a single cell covers both. The 3-cell Li-Polymer configuration matches the original charge controller's expected impedance and EEPROM communication profile.
  • Bench tested on actual hardware: We cycled this cell on a UX305UA unit and confirmed the BMS initialised correctly, charge acceptance reached full capacity without cutoff errors, and the system reported normal battery status within two charge cycles.
  • Post-install calibration for the UX305UA: After fitting this cell, run one full discharge to the hibernate cutoff point, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning the firmware typically throws after any cell swap.

BIOS reporting poor battery health immediately after fitting the new cell

The Zenbook UX305UA stores battery health data in EEPROM on the old cell. When you fit a new cell, the BIOS reads residual or zeroed EEPROM values and flags the battery as degraded or unknown — even though the cell is new. This is a firmware read issue, not a hardware fault. Running two full charge and discharge cycles allows the battery learn cycle to overwrite the stale EEPROM data. After the second full cycle, the BIOS health indicator should return to normal.

Laptop shutting down unexpectedly at 20–30% charge shown

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The IC maps voltage to percentage using data from the old, degraded cell — so the estimated percentage drops faster than the real state of charge. Under combined CPU and display load, the voltage reading hits the BMS cutoff threshold while the gauge still shows 20–30% remaining. Run two full discharge-to-hibernate then full-charge cycles to let the fuel gauge IC recalibrate. After calibration the reported percentage will align with actual cell voltage, and the unexpected shutdowns will stop.

Compatible Models

Zenbook UX305UA Zenbook UX305UAB UX305UA UX305UAB

Replaces Part Numbers

C31N1539 0B200-01180200

Technical Specifications

Voltage11.55V
Amp Hours4850mAh
Capacity4850mAh
Rate56.02Wh
Net Weight221.2g /7.80 oz
Gross Weight481.2g /16.97 oz
Approximate Weight481.2g /16.97 oz
Dimension 297.20 x 112.50 x 4.00mm

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

Windows is showing the battery as 0% or "plugged in, not charging" right after I installed the new cell — what's wrong?

The fuel gauge IC is reading EEPROM data from the old cell and has not yet mapped the new cell's charge curve. Plug the laptop in, let it charge uninterrupted to 100%, then run it down to hibernate cutoff without interrupting the discharge. Repeat this once more. After two full cycles the IC recalibrates against the new cell and the percentage reading stabilises. If Windows still shows 0% after two cycles, check the battery connector is fully seated — a partially connected cell causes the same symptom.

My Zenbook shows the new battery's capacity as noticeably lower than the rated 56.02Wh in the system info — is the cell underspec?

The Wh figure in Windows or BIOS is pulled from the cell's EEPROM, which stores the rated design capacity rather than a live measured value. A new Li-Polymer cell also does not deliver full rated capacity until the electrolyte has gone through two or three charge and discharge cycles. Run two full cycles and then recheck the reported Wh — it will rise closer to 56.02Wh as the cell conditions. If the figure stays significantly below rated capacity after three cycles, the cell has a fault.

The battery charges normally but the BIOS health screen still says "battery replacement recommended" after a week — how do I clear it?

That warning is written by the BIOS battery learn cycle and does not clear automatically on a new cell install. The BIOS needs to observe a complete discharge from 100% to hibernate cutoff followed by an uninterrupted charge back to 100% before it overwrites the stale health flag. Enter the BIOS after the cycle completes — on the UX305UA this is the MyASUS or BIOS Battery Health screen — and confirm the status has updated. One full learn cycle is usually enough; if the flag persists, run a second cycle before assuming a firmware issue.

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