Asus VivoBook S300 Replacement Battery C31-X402 11.1V 4000mAh
Check that your old battery model number and device model to match our description. This makes sure they work together.
We ship your order same day if you buy it before 4 PM EST.
Asus VivoBook S300 Replacement Battery C31-X402 11.1V 4000mAh - is backordered and will ship as soon as it is back in stock.
Let customers speak for us
Send Your Battery Photo
Expert Technician Help
Snap a photo or video of your battery and send it to us. We'll identify the exact replacement—fast and hassle-free. Our team has helped thousands of customers find the right battery quickly and easily.
POST YOUR BATTERY IMAGE
Product & Solutions Expert
✉ sales@batteryweb.com
Battery Care Tips
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
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
⚠️ 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.
Asus VivoBook S300 Replacement Battery C31-X402 11.1V 4000mAh - is backordered and will ship as soon as it is back in stock.
Voltage
11.1V
Amp
4000mAh
Asus VivoBook S300 / S400 Series — 11.1V Li-Polymer Replacement Battery (C31-X402)
This is an 11.1V, 4000mAh (44.4Wh) Li-Polymer battery for the Asus VivoBook S300, S400, S400C, and S400CA. It replaces OEM part numbers C31-X402, 0B110-00210000, C21-X401, and C31X402. If your original cell is swelling, failing to charge, or no longer holding power, this is a direct cell swap.
- VivoBook S300 / S400 platform fit: These models share the same 11.1V three-cell Li-Polymer battery bay, connector pinout, and BMS communication protocol. The S400C and S400CA variants use the same pack form factor — 302 x 69.42 x 7.82mm — with the same fuel gauge IC handshake, so one SKU covers the full lineup.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a VivoBook S400 unit. The BMS accepted the pack without fault codes, the charge controller stepped through its CC/CV stages cleanly, and the fuel gauge IC registered the cell correctly within two full cycles.
- Post-install discharge cycle on VivoBook S300 / S400: 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 on the first boot after any cell swap.
BIOS reporting poor battery health immediately after fitting a new cell
The VivoBook BIOS stores battery health data in EEPROM on the old pack. When a new cell is fitted, the BIOS reads zero cycle history and flags the pack as degraded or unknown. This is not a fault with the replacement cell — it is the BIOS comparing fresh EEPROM data against its stored baseline. Run one complete discharge-to-hibernate followed by a full uninterrupted charge. After two to three cycles, the fuel gauge IC recalibrates and the BIOS health status updates to reflect the actual cell condition.
VivoBook S300 / S400 shutting down at 20–30% charge shown
This happens when the fuel gauge IC is still calibrated against the old, degraded cell's voltage curve. The display shows 25% remaining while the actual cell voltage has already dropped below the BMS cutoff threshold under combined CPU and display load. The laptop cuts power before the OS can trigger a graceful shutdown. Run two full discharge-to-hibernate cycles — the fuel gauge IC maps the new cell's voltage curve and the reported percentage aligns with the real state of charge, typically resolving the early cutoff after cycle two.
Compatible Models
Replaces Part Numbers
Technical Specifications
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 VivoBook S400 shows the new battery as 0% or "unknown" in Windows right after installing — is the cell faulty?
No — the Windows fuel gauge IC is still calibrated to the old cell's EEPROM data and cannot yet read the new pack accurately. Fully discharge the laptop to hibernate cutoff, then charge it uninterrupted to 100%. After two full cycles, the fuel gauge maps the new cell's voltage curve and the percentage reading stabilises.
The Asus battery info screen shows the wrong Wh rating after fitting this cell — it reads lower than the spec on the pack.
The Wh figure shown in the BIOS or Asus Battery Health Charging utility pulls from the EEPROM on the old cell, not from a live measurement of the new pack. The new cell's EEPROM carries the rated chemistry value for C31-X402, which the BIOS reads as-is before any calibration cycles run. Complete two full discharge-to-100% charge cycles and the reported Wh figure will update to reflect the actual cell data — confirm it reads 44.4Wh after cycle two.
The VivoBook S300 charges to 80% and stops — the charge indicator light goes solid and Windows says "plugged in, not charging."
This is the BIOS-controlled charge limit in Asus Battery Health Charging — it is firmware behaviour, not a cell fault. Open the MyASUS app or Battery Health Charging utility and check which mode is active: Balanced Mode caps charge at 80%, Full Capacity Mode allows 100%. Switch to Full Capacity Mode, unplug and replug the adapter, and the charge will resume from 80% to 100%.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
Related Products
Engineered for Performance. Built to Last.
Check out our top-rated selection of reliable products built to last. We offer high-quality options that deliver consistent performance for all your needs.
-
Up to 17% offNew arrival
BatteryWeb
Samsung 900X4B-A02 Replacement Battery 7.4V 8400mAh
1.26 lb
Sale priceFrom $146.99 USD Regular price $177.99Unit priceIn stock (42 units) -
-
Up to 17% offNew arrival
BatteryWeb
Dell Inspiron 15RV MR90Y Replacement Battery 14.8V 2700mAh
1.09 lb
Sale priceFrom $99.99 USD Regular price $119.99Unit priceIn stock (303 units) -
-
Up to 19% offNew arrival
BatteryWeb
Samsung XE303C12 Chromebook Replacement Battery 7.5V AA-PBZN2TP
0.91 lb
Sale priceFrom $61.99 USD Regular price $75.99Unit priceIn stock (63 units) -
-
Up to 18% offNew arrival
BatteryWeb
Lenovo IdeaPad Yoga 11 L11M4P13 Compatible Battery 14.8V
1.14 lb
Sale priceFrom $125.99 USD Regular price $152.99Unit priceIn stock (30 units) -
-
Up to 18% offNew arrival
BatteryWeb
Apple MacBook Pro 15" i7 Replacement Battery 10.95V 7070mAh
1.58 lb
Sale priceFrom $130.99 USD Regular price $158.99Unit priceIn stock (69 units) -
-
Up to 18% offNew arrival
BatteryWeb
Samsung Ativ Pro AA-PLZN4NP Replacement Battery 7.5V 6540mAh
1.13 lb
Sale priceFrom $125.99 USD Regular price $152.99Unit priceIn stock (63 units) -
-
Up to 18% offNew arrival
BatteryWeb
Samsung NP350U2A Replacement Battery 7.4V 6350mAh AA-PBZN6PN
1.12 lb
Sale priceFrom $125.99 USD Regular price $152.99Unit priceIn stock (15 units) -
-
Up to 17% offNew arrival
BatteryWeb
L12S4Z01 Lenovo IdeaPad S300 Replacement Battery 14.8V 2200mAh
1.02 lb
Sale priceFrom $107.99 USD Regular price $129.99Unit priceIn stock (48 units) -
