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Thunderobot ST-PLUS Replacement Battery 11.1V 4400mAh

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From $73.99 USD $91.99
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Fits Thunderobot ST-PLUS, ST-PLUS TB, PLUS-U5G, PLUS-U5F notebooks with 11.1V OEM battery slots.
11.1V at 4400mAh delivers 48.84Wh — matches original capacity for full session work away from outlets.
Connector slides into factory slot with no adapter; locking tab engages the same way as OEM cells.
We charged this cell in an ST-PLUS unit; BMS initialized clean on first insert, voltage held steady under load.
After install, run one full discharge to hibernation cutoff, then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears the inaccurate health warnings that appear after every cell swap.
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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Check that your old battery model number and device model to match our description. This makes sure they work together.

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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

11.1V

Amp

4400mAh

Thunderobot ST-PLUS Series — 11.1V Li-ion Replacement Battery

This is an 11.1V, 4400mAh (48.84Wh) Li-ion battery for the Thunderobot ST-PLUS, ST-PLUS TB, PLUS-U5G, and PLUS-U5F laptops. It replaces a degraded or failed original cell and restores the notebook's ability to run away from mains power. Voltage and connector spec match the original pack exactly.

  • ST-PLUS platform compatibility: The ST-PLUS, ST-PLUS TB, PLUS-U5G, and PLUS-U5F share the same 11.1V three-cell configuration, connector pinout, and BMS communication protocol — which is why one cell fits all of them.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on ST-PLUS hardware. The BMS handshake completed without fault codes, and the pack held voltage across the full discharge curve without sagging early.
  • Post-install calibration cycle: After fitting this battery, run the laptop on battery until it hibernates at low charge, then charge it uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting battery health as poor after replacement

The Thunderobot BIOS reads health data stored in the old cell's EEPROM and compares it against the new pack. When the values don't match its learned baseline, it flags the battery as degraded even though the cell is new. This is not a fault with the replacement — it's a calibration gap. Run one full discharge-to-hibernate cycle followed by a full uninterrupted charge, and the BIOS will rewrite its health baseline against the new cell's actual data.

Laptop shutting down at 20–30% charge shown

This happens when the fuel gauge IC's capacity model still reflects the old cell's degraded chemistry. Under full CPU and display load, the new cell's actual voltage doesn't match where the gauge thinks it is — so the laptop cuts power before the battery is genuinely empty. Run two to three full discharge and charge cycles to let the fuel gauge IC recalibrate against the new cell. After calibration, the reported percentage and actual cutoff voltage — around 9V — should align correctly.

Compatible Models

ST-PLUS ST-PLUS TB PLUS-U5G PLUS-U5F PLUS-U5TA

Technical Specifications

Voltage11.1V
Amp Hours4400mAh
Capacity4400mAh
Rate48.84Wh
Net Weight323.4g /11.41 oz
Gross Weight473.4g /16.70 oz
Approximate Weight473.4g /16.70 oz
Dimension 208.10 x 61.20 x 24.50mm

Product Highlights

  • Brand: Thunderobot
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

BIOS says the battery health is poor right after I installed a brand new cell — is it faulty?

The BIOS pulls health data from the old cell's EEPROM and compares it to a learned baseline that no longer applies. A new cell looks "unknown" or "degraded" until the system rewrites that baseline. Run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. That single learn cycle clears the warning on most Thunderobot ST-PLUS units.

The battery percentage jumps around wildly for the first few charges — what's causing that?

The fuel gauge IC on the ST-PLUS motherboard calibrates its capacity model against cycle history from the old cell. With a new cell installed, the model is off and the percentage reading is unreliable until it catches up. Give it two to three full discharge and charge cycles without interrupting the charge. After that, the gauge IC locks onto the new cell's actual chemistry and the percentage stabilises.

System info shows the wrong Wh rating for this battery — it doesn't match what I ordered?

The Wh value shown in Windows or the BIOS is read from EEPROM data embedded in the battery pack, not calculated live from the cells. If the EEPROM reports a different rated figure than the label, it reflects a difference between the pack's programmed nominal value and the actual cell chemistry. The real-world capacity of 48.84Wh is what matters for performance — confirm it by checking the charge cycle in your OS battery report after two full cycles.

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