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Amazon Kindle Fire HD 8th ST33 Replacement Battery 3.8V 4750mAh

Up to 19% off
New arrival
From $33.99 USD $41.99
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Fits Amazon Kindle Fire HD 8th generation tablet, replaces ST33, 26S1021, 58-000303, 58-000313.
3.8V, 4750mAh lithium-polymer cell restores full runtime to aged Fire HD 8th tablets.
Connector slides into original battery slot with positive terminal forward, no adhesive removal needed.
Bench test showed clean BMS handshake on first charge with no fault codes or cutoff anomalies.
After installation, fully discharge the tablet to automatic shutoff then charge uninterrupted to 100% — this recalibrates the fuel gauge IC against the new cell and eliminates inaccurate percentage display.
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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

4750mAh

Amazon Kindle Fire HD 8th Generation — 3.8V Li-Polymer Replacement Battery (ST33)

This 3.8V, 4750mAh lithium-polymer cell replaces part number ST33 in the Amazon Kindle Fire HD 8th generation tablet, covering device variants K72LL3 and K72LL4. It restores power to tablets where the original cell no longer holds a charge or fails to power on. Capacity matches OEM spec at 18.05Wh.

  • K72LL3 and K72LL4 compatibility: Both variants share the same 3.8V power rail, connector pinout, and charge IC handshake, so one cell covers the full 8th generation Fire HD 8 lineup without modification.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on a Fire HD 8 unit. The BMS accepted the charge IC handshake on the first cycle and held voltage within spec across display-on and idle states.
  • Fuel gauge recalibration after swap: After installing this battery, run the tablet from 100% down to automatic shutoff without interruption, then charge uninterrupted back to 100%. This resets the fuel gauge IC against the new cell and corrects the inaccurate percentage readings that typically appear after a battery replacement.

Kindle Fire HD 8 shutting down at 15–25% remaining

The Fire HD 8 runs a combined load from its display backlight and WiFi radio simultaneously. When the battery cell ages, voltage drops sharply under this combined draw — the BMS reads the sag as a low-voltage fault and triggers shutdown before the percentage counter reaches zero. A new cell with full capacity holds voltage flatter under load, eliminating early cutoffs. After fitting this replacement, complete one full discharge cycle so the fuel gauge IC maps the actual voltage curve of the new cell.

Fire HD 8 showing wrong battery percentage after replacement

The fuel gauge IC on the Fire HD 8 stores a learned voltage profile of the old, degraded cell. When a new cell goes in, that stored profile no longer matches reality, so the percentage reading jumps, drops, or stalls. This is not a fault with the replacement battery — it is a calibration mismatch. Fix it by discharging fully to automatic shutoff, then charging uninterrupted to 100%; the gauge IC resets its reference at 4.2V full charge and recalibrates from there.

Compatible Models

Kindle Fire HD 8th K72LL3 K72LL4

Replaces Part Numbers

ST33 26S1021 58-000303 58-000313

Technical Specifications

Voltage3.8V
Amp Hours4750mAh
Capacity4750mAh
Rate18.05Wh
Net Weight80.6g /2.84 oz
Gross Weight220.6g /7.78 oz
Approximate Weight220.6g /7.78 oz
Dimension 120.00 x 99.10 x 2.80mm

Product Highlights

  • Brand: Amazon
  • 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 Kindle Fire HD 8 still shows the wrong battery percentage two days after fitting the new battery — is something wrong with the cell?

Nothing is wrong with the cell. The fuel gauge IC retained the degraded voltage curve from the old battery and is still reporting against that profile. Drain the tablet completely until it shuts itself off, then charge it uninterrupted to 100% without unplugging early. That single full cycle resets the gauge IC's reference points and clears the inaccurate readings.

Fast charging stopped working on my Fire HD 8 after I swapped the battery — it only charges slowly now.

The Fire HD 8 charge IC needs to complete at least one accepted charge cycle with the new cell before it re-enables higher charge rates. Some units also reset USB negotiation after a battery replacement. Plug into the original Amazon power adapter, not a third-party charger, and let it run one full uninterrupted charge to 100%. If fast charging does not resume after that cycle, confirm the adapter output is 9V/1.2A — lower-voltage adapters will only ever trickle charge.

My Kindle Fire HD 8 gets warm near the bottom edge while charging the new battery — should I be worried?

Warmth at the bottom edge is where the charge IC and power management circuitry sit, not a sign of a faulty cell. A new lithium-polymer cell draws closer to its rated charge current in the first few cycles, so the charge IC runs slightly warmer than it did with a degraded battery pulling less current. If the tablet becomes hot to the touch or shows a temperature warning on screen, disconnect and allow it to cool. Normal charging warmth stays well below 40°C and fades after the first few cycles.

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