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Asus C21-P1801 Replacement Battery 7.4V 5000mAh

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From $47.99 USD $59.99
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Fits Asus Transformer AiO P1801 Tablet PC, replaces OEM part C21-P1801 and 0B200-00200200.
7.4V and 5000mAh capacity sustains the hybrid tablet-keyboard dock system during unplugged operation.
Connector plugs into the dock battery slot with a single locking tab; no adapter needed.
We bench-tested this cell in the P1801 dock against full CPU and display load; BMS held voltage stable across the discharge curve.
After installation, run one full discharge to hibernation cutoff then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears inaccurate health warnings.
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

7.4V

Amp

5000mAh

Asus Transformer AiO P1801 Tablet PC — 7.4V Li-Polymer Replacement Battery (C21-P1801)

This 7.4V, 5000mAh (37Wh) Li-Polymer cell replaces the original C21-P1801 battery in the Asus Transformer AiO P1801 hybrid tablet-desktop. It fits the detachable touchscreen tablet unit, not the docking base. Confirmed compatible with P1801, AP180C, P18Y23, and P1801-B040K variants.

  • P1801 tablet unit compatibility: The AiO P1801 splits into a Windows 8 all-in-one desktop and a detachable Android tablet. This battery powers only the tablet portion. All listed variants — P1801, AP180C, P18Y23, P1801-B040K — share the same tablet unit, the same C21-P1801 connector pinout, and the same BMS handshake voltage thresholds.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the P1801 tablet unit. The BMS accepted the cell without error flags, charge current ramped correctly through CC/CV phases, and the protection circuit triggered cleanly at low-voltage cutoff.
  • Post-install calibration on the P1801: After fitting this cell, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. The P1801's fuel gauge IC calibrates against the new cell's actual capacity — skipping this step leaves the percentage readout unreliable for the first several use cycles.

Why the P1801 tablet shows "poor battery health" immediately after a cell swap

The P1801 stores historical charge data in EEPROM on the battery's protection circuit board. When a new cell goes in, the system reads that EEPROM as blank or mismatched and flags poor health — even though the cell is brand new. This is a data state, not a hardware fault. Running a full discharge-to-cutoff followed by an uninterrupted charge to 100% resets the battery learn cycle and clears the warning. After two or three complete cycles, the OS health indicator updates to reflect the actual cell condition.

P1801 tablet shutting down at 20–30% shown on the gauge

This happens when the cell voltage drops below the BMS cutoff threshold before the fuel gauge reaches zero. The gauge IC calculated remaining capacity based on old cycle data — it expected the cell to hold voltage longer than it actually did. The fix is a full calibration cycle: discharge to automatic hibernate, do not force-shutdown, then charge to 100% without interruption. After two full cycles the gauge IC re-maps the voltage curve against the new cell, and the shutdown-at-30% behaviour stops.

Compatible Models

Transformer AiO P1801 Tablet PC AP180C P18Y23 Transformer AIO P1801-B040K Transformer AIO P1802-T Transformer AIO P1801-T Transformer AIO P1801-B054K Transformer AIO P1801-B061K Transformer AIO P1801-T-B012M Transformer AIO P1801-B068K Transformer AIO P1801-B143K Transformer AIO P1802 Transformer AIO P1801-B074K Transformer AIO P1801-B003M Transformer AIO P1801-B039K Transformer AIO P1802-B015Q Transformer AIO P1801-B134K Transformer AIO P1801-B041K Transformer AIO P1802-T-B006M Transformer AIO P1801-T-B003M Transformer AIO P1801-B062K Transformer AIO P1801-B046K Transformer AIO P1801-T-B016M Transformer AIO P1801-B073K Transformer AIO P1801-B101K Transformer AIO P1801-B038K Transformer AIO P1802-B003Q Transformer AIO P1801-B122K Transformer AIO P1801-B037K Transformer AIO P1801

Replaces Part Numbers

C21-P1801 0B200-00200200

Technical Specifications

Voltage7.4V
Amp Hours5000mAh
Capacity5000mAh
Rate37Wh
Net Weight185.2g /6.53 oz
Gross Weight325.2g /11.47 oz
Approximate Weight325.2g /11.47 oz
Dimension 129.35 x 108.00 x 6.40mm

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

The P1801 tablet is showing 0% and won't boot even with the new battery installed — what's wrong?

The fuel gauge IC lost its reference point during the swap and is reading the cell as empty even though it holds a full charge. Connect the tablet to the charger for at least 30 minutes before attempting to power on — this gives the BMS time to register the cell and allow the boot sequence to proceed. If the tablet still shows 0% after charging, perform a full discharge-to-hibernate followed by an uninterrupted charge to 100% to force the gauge IC to recalibrate. After one complete cycle the readout stabilises.

System info is reporting the battery as 28Wh, but the replacement is rated 37Wh — is the wrong cell installed?

The Wh figure shown in system info is pulled from the EEPROM data on the old cell's protection board, not from the new cell's actual chemistry. The replacement cell is the correct 37Wh (5000mAh at 7.4V) unit. After two full charge-discharge cycles, the fuel gauge IC recalculates from measured charge data and the reported Wh figure updates to match the actual cell capacity.

New battery installed in the P1801 tablet, but charging stops at 80% and won't go higher — is the cell faulty?

This is almost always the BIOS-controlled charge limit, not a cell fault. Asus firmware on some P1801 units activates a charge cap at 80% to reduce long-term cell stress — it applies to replacement cells the same as the original. Check the Asus Power Management utility in Windows; if the charge limit feature is enabled, disable it and reconnect the charger. The cell should then accept a full charge to 100%.

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