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Asus VivoBook S451 C21N1335 Replacement Battery 7.5V 5050mAh

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From $62.99 USD $76.99
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Fits Asus VivoBook S451, S451LA, S451LB, and S451LN models; replaces OEM C21N1335 and 0B200-00530100 batteries.
7.5V, 5050mAh lithium-polymer pack delivers 37.88Wh for full-day portable operation on this 14-inch ultrabook.
Connector slides into the proprietary Asus slot on the underside; locking tab secures the pack flush against the chassis frame.
We ran a full discharge cycle on the test rig; the BMS held voltage stability through the final 10% before cutoff engaged.
After installation, discharge fully to hibernation 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

7.5V

Amp

5050mAh

Asus VivoBook S451 Series — 7.5V Li-Polymer Replacement Battery (C21N1335)

This is a 7.5V, 5050mAh (37.88Wh) lithium-polymer battery for the Asus VivoBook S451 family of 14-inch ultrabook laptops. It fits the S451, S451LA, S451LB, S451LN, and over a dozen other S451 variants. It matches the OEM cell dimensions at 196.70 x 82.50 x 9.15mm for a direct internal fit.

  • S451 family compatibility: Every S451 variant in this lineup runs the same 7.5V two-cell configuration with the same connector pinout and BMS handshake protocol. One battery covers the entire range without wiring adapters or firmware workarounds.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an S451LB unit. The BMS communicated correctly with the EC at first contact, charge current stepped down normally as the cell approached capacity, and the fuel gauge IC tracked state of charge without erratic jumps.
  • First-install calibration on S451 units: After fitting this battery, run the laptop down to hibernate cutoff on a real workload — not idle — then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to complete against the new cell and clears the inaccurate health warning that almost always appears after a cell swap on this platform.

BIOS reporting battery health as poor immediately after fitting the new cell

The S451 stores capacity and cycle data in EEPROM on the battery's protection circuit. When you swap cells, the BIOS reads stale data from the old cell's final state and flags the new battery as degraded before it has run a single cycle. This is not a fault with the replacement cell. Run one full discharge to hibernate cutoff, then charge uninterrupted to 100% — the BIOS learn cycle will update the EEPROM health data and the warning clears on the next boot.

VivoBook S451 shutting down abruptly at 20–30% charge shown

This happens when the cell voltage drops below the BMS cutoff threshold under combined CPU and display load before the fuel gauge IC reaches its low-battery warning point. The fuel gauge IC on the S451 calibrates its voltage-to-percentage curve over several full cycles. On a brand-new cell, this curve is not yet accurate and the laptop hits voltage cliff before the OS can issue a shutdown warning. Run three full charge and discharge cycles to allow the fuel gauge IC to build an accurate capacity map. After calibration, the reported percentage and actual cutoff voltage should align within a few percent.

Compatible Models

VivoBook S451 VivoBook S451LA VivoBook S451LB VivoBook S451LN K451LN VivoBook S451LN-CA004H VivoBook S451LN-CA021H VivoBook S451LN-CA132H K451LN-WX162H VivoBook S451LN-CA009H VivoBook S451LN-CA032H VivoBook S451LN-CA159H VivoBook S451LN-CA020H VivoBook S451LN-CA036H VivoBook S451LN-CA160H K451L S451LN

Replaces Part Numbers

C21N1335 0B200-00530100

Technical Specifications

Voltage7.5V
Amp Hours5050mAh
Capacity5050mAh
Rate37.88Wh
Net Weight181.8g /6.41 oz
Gross Weight321.8g /11.35 oz
Approximate Weight321.8g /11.35 oz
Dimension 196.70 x 82.50 x 9.15mm

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 S451 shows the new battery as 0% or "unknown" and won't boot off it — what's going on?

The EC on the S451 requires the BMS to complete its initial handshake before reporting state of charge. If the connector wasn't fully seated or the battery protection circuit tripped during shipping, the EC gets no data and reports 0% or unknown. Disconnect AC power, reseat the battery connector firmly, then connect AC and let the cell charge for 20 minutes before attempting to boot. If it still reads 0%, press and hold the power button for 15 seconds with AC connected to force an EC reset.

Windows is reporting this battery as 38Wh but the health tab shows a different design capacity — is the cell wrong?

The Wh figure Windows reads comes from EEPROM data embedded in the battery's protection circuit — it reflects the rated chemistry spec of 37.88Wh, which matches this cell. The "full charge capacity" figure in the health tab is what the fuel gauge IC actually measured during the last charge cycle. On a new cell that hasn't completed a calibration cycle yet, these two numbers will differ. Run one full discharge to hibernate cutoff followed by an uninterrupted charge to 100% and the measured figure will converge toward the rated 37.88Wh.

The S451 charges fine but the battery percentage jumps around wildly — drops 15% in seconds then climbs back up.

The fuel gauge IC on the S451 uses a voltage-to-capacity lookup table that was tuned to the original cell's discharge curve. A replacement cell with slightly different internal resistance throws off that curve, causing erratic percentage readings for the first few cycles. This is a calibration gap, not a defective cell. Run three complete discharge-to-hibernate and charge-to-100% cycles under normal use load, and the fuel gauge IC will rebuild its curve against the new cell's actual characteristics.

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