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Amazon Kindle Fire HDX Replacement Battery 3.8V 4550mAh

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From $31.99 USD $39.99
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Fits Amazon Kindle Fire HDX models with part number S12-T1-S and equivalent OEM designations.
3.8V and 4550mAh capacity restore full tablet power for display, processor, and WiFi use.
Connector is proprietary Amazon contact plate with flat orientation and positive tab alignment.
We bench tested this cell on Kindle Fire HDX charging circuit — BMS accepted charge cycle without fault codes and held steady voltage under combined display and WiFi load.
After installation, run one full discharge to automatic shutoff then charge uninterrupted to 100% — this resets the fuel gauge IC calibration against the new cell and resolves inaccurate percentage display that appears after a swap.
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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

3.8V

Amp

4550mAh

Amazon Kindle Fire HDX — 3.8V Li-Polymer Replacement Battery (S12-T1-S)

This 3.8V, 4550mAh lithium-polymer battery replaces the original cell in the Amazon Kindle Fire HDX and Kindle Fire HDX 7 (model C9R6QM). It restores power to the display, processor, and wireless radios when the factory battery no longer holds a charge. Dimensions are 125.40 × 68.20 × 4.00mm — measure your original before installing.

  • HDX 7 and C9R6QM compatibility: These models share the same battery bay geometry, connector pinout, and charge IC handshake protocol, which is why OEM part numbers S12-T1-S, S12-T1, and 58-000043 all cross-reference to a single cell specification.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Kindle Fire HDX platform. The BMS accepted the charge IC handshake without error flags, and voltage held stable under combined display and WiFi load.
  • Fuel gauge recalibration after swap: After installing this battery, run the tablet down to automatic shutoff, then charge uninterrupted to 100%. This forces the fuel gauge IC to recalibrate against the new cell and clears the inaccurate percentage readings that typically appear after a battery replacement.

Kindle Fire HDX shutting down between 15% and 25% remaining

This is a voltage cliff problem, not a capacity problem. When the display brightness is high and WiFi is active simultaneously, combined current draw pulls cell voltage below the BMS cutoff threshold before the fuel gauge reaches 0%. The tablet reads 15–25% but the cell voltage has already dropped to roughly 3.2V under load. One full recalibration cycle — drain to shutoff, full uninterrupted charge — tightens the fuel gauge mapping and moves the cutoff trigger closer to the actual empty point.

Fast charging not available after battery replacement on the HDX

The Kindle Fire HDX charge controller requires at least one complete accepted charge cycle before it negotiates higher current draw with the charger. Immediately after a swap, the charge IC defaults to a conservative current profile while it characterises the new cell. Use the original Amazon power adapter — third-party adapters that don't send the correct voltage handshake will keep the device in slow-charge mode indefinitely. Complete one full charge to 100% with the OEM adapter and fast charging behaviour returns.

Compatible Models

Kindle Fire HDX Kindle Fire HDX 7 C9R6QM

Replaces Part Numbers

S12-T1-S S12-T1 58-000043 S12-T1-L MNHSNY133711TM 26S1004-A

Technical Specifications

Voltage3.8V
Amp Hours4550mAh
Capacity4550mAh
Rate17.29Wh
Net Weight73g /2.58 oz
Gross Weight108g /3.81 oz
Approximate Weight108g /3.81 oz
Dimension 125.40 x 68.20 x 4.00mm

Product Highlights

  • Brand: Amazon
  • Manufacturer: CS
  • Series: X-Longer
  • Color: Black
  • Product Type: Li-Polymer
  • Battery Type: Li-Polymer
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Kindle Fire HDX shows a completely different battery percentage after I replaced the battery — it jumped from 40% to 80% without charging. What's happening?

The fuel gauge IC inside the tablet was calibrated to the resistance and discharge curve of the old cell. When a new cell goes in, the IC has no reference point, so it misreports state of charge — sometimes wildly. Run the tablet down to automatic shutoff, then charge it uninterrupted to 100% using the Amazon adapter. That single full cycle gives the fuel gauge IC enough data to remap its calibration to the new cell.

The Kindle Fire HDX feels warm on the back while it's charging after the battery swap — is the new cell overheating?

Warmth during the first few charge cycles on a new lithium-polymer cell is normal. The charge IC runs at a slightly higher current while it characterises the new cell's internal resistance, which generates more heat than steady-state charging does. If the tablet is warm but not hot to the touch and charging progresses normally, no action is needed. If the back gets genuinely hot and charging stops, check that the replacement cell OEM part number matches S12-T1-S and that the connector is fully seated.

Battery percentage on my Kindle Fire HDX drops fast from 100% but then slows down — the first 30% disappears quickly and the rest takes much longer. Is the battery faulty?

This is fuel gauge drift, not a faulty cell. The charge IC hasn't finished mapping the new cell's voltage-to-capacity curve, so the top of the range looks artificially compressed. The drop accelerates because the IC is still using the old cell's curve as a reference, which skews high at full charge. Run one complete discharge to automatic shutoff followed by a full uninterrupted charge to 100% — after that cycle the percentage should track evenly across the full range.

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