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Fujitsu Esprimo Mobile V5505 Replacement Battery BTP-BAK8 11.1V

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From $65.99 USD $81.99
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Fits Fujitsu Esprimo Mobile V5505 and replaces OEM part numbers BTP-BAK8, BTP-B4K8, BTP-B5K8, BTP-B7K8, BTP-B8K8, BTP-C0K8, BTP-C0L8, BTP-C1K8, BTP-C2L8, BTP-C3K8, BTP-C4K8, SQU-518, and SQU-522.
This cell delivers 11.1V at 4400mAh capacity, storing 48.84Wh for full workday mobile use without AC power.
Connector seats flush into the battery slot with a standard locking tab; verify the contact pins align before closing the retention clip.
We bench-tested this pack against the V5505 motherboard; the BMS accepted the cell on first insertion and held stable voltage through a full discharge cycle.
After installing, run one complete discharge to hibernation cutoff then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears false 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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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

11.1V

Amp

4400mAh

Fujitsu Esprimo Mobile V5505 Series — 11.1V Li-ion Replacement Battery (BTP-BAK8)

This is an 11.1V, 4400mAh (48.84Wh) Li-ion replacement battery for the Fujitsu Esprimo Mobile V5505, V5545, V6505, and V6535 notebooks. It uses OEM part number BTP-BAK8 and shares compatibility across the broader Esprimo Mobile line that runs on the same 11.1V three-cell architecture. Physical dimensions are 206.64 x 50.26 x 24.00mm — check your bay clearance before ordering.

  • Esprimo Mobile V-series compatibility: The V5505, V5545, V6505, and V6535 share the same battery bay dimensions, connector pinout, and BMS handshake protocol. Fujitsu used a consistent three-cell 11.1V rail across these Esprimo Mobile variants, which is why one part number covers all of them.
  • Bench tested on actual hardware: We cycled this cell through full charge and load discharge on the V-series platform. The BMS authenticated without fault codes, charge termination triggered correctly at 12.6V, and cell balancing held within spec across all three groups.
  • First-cycle calibration on the V5505: After installing, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.

BIOS reporting poor battery health immediately after fitting a new cell

The Esprimo Mobile BIOS reads health data from EEPROM stored on the battery's protection circuit, not from a live cell measurement. When a new cell arrives, that EEPROM carries factory default values that don't match the BIOS's learned baseline for the old pack. The system flags this as degraded health even though the cell is new. Run one full discharge-to-hibernate, then a full uninterrupted charge — the BIOS battery learn cycle overwrites the stale EEPROM reference and the health warning clears.

Laptop shuts down abruptly at 20–30% charge shown

This happens when the fuel gauge IC hasn't calibrated against the new cell's actual voltage curve. The OS reads 25% remaining, but the cell hits a voltage cliff under combined CPU and display load that the uncalibrated gauge didn't predict, and the BMS cuts power to protect the cells. It is not a faulty battery — it is a gauge mismatch. Complete two full discharge-to-hibernate and full recharge cycles. After that, the fuel gauge IC recalculates its discharge curve against the real cell and the early shutdowns stop. Verify the fix by checking that the BIOS reports cell voltage above 10.8V at the 20% mark.

Compatible Models

Esprimo Mobile V5505 Esprim Mobile V5545 Esprim Mobile V6505 Esprim Mobile V6535 Esprim Mobile V6545 Esprim Mobile V5545 Amilo Li1718 Amilo Li1720 Amilo Li2727 Amilo Li2732 Amilo Li2735 Amilo Pro V3405 Amilo Pro V3505 Amilo Pro V3525 Amilo Pro V8210 Esprimo Mobile V5545 Esprimo Mobile V6505 Esprimo Mobile V6535 Esprimo Mobile V6545

Replaces Part Numbers

BTP-BAK8 BTP-B4K8 BTP-B5K8 BTP-B7K8 60.4P311.041 60.4U50T.011 BTP-B8K8 60.4P311.051 60.4P50T.011 BTP-C0K8 BTP-C0L8 BTP-C1K8 BTP-C2L8 BTP-C3K8 BTP-C4K8 60.4B90T.061 0.4U50T.011 60.4V70T.011 60.4V70T.031 S26393-E005-V161-02-0746 S26393-E005-V161-01-0746 S26391-F400-L400 MS2191 MS2192 MS2216 MS2228 MS2238 MS2239 3UR18650-2-T0169 60.4P311.001 MS2193 916C4850F S26391-F6125-L100 SQU-518 SQU-522 3UR18650F-2-QC-12 3UR18650F-2-QC12W S280N-055 916C5450f

Technical Specifications

Voltage11.1V
Amp Hours4400mAh
Capacity4400mAh
Rate48.84Wh
Net Weight288.4g /10.17 oz
Gross Weight438.4g /15.46 oz
Approximate Weight438.4g /15.46 oz
Dimension 206.64 x 50.26 x 24.00mm

Product Highlights

  • Brand: Fujitsu
  • 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

My Esprimo Mobile V5505 shows the battery as 0% or "unknown" right after fitting the new pack — what's wrong?

The BIOS hasn't completed its battery learn cycle against the new cell's EEPROM data yet, so it reports the state as unknown or zero. This is a firmware read issue, not a dead battery. Plug into AC power and let the pack charge fully without interruption, then do one full discharge to hibernate-cutoff. After that cycle the BIOS recognises the new cell and the reading normalises.

Windows is showing the new battery's capacity as a different Wh rating than what's printed on the pack — is the cell wrong?

The Wh value Windows displays is pulled from the EEPROM on the battery's protection circuit, which carries a rated design capacity figure that can differ slightly from the cell's actual chemistry capacity. The physical cell is correct — the discrepancy is a data field difference between EEPROM-stored design spec and real-world rated capacity. Check the cell voltage under load instead: a healthy fully-charged 11.1V Li-ion pack should read between 12.4V and 12.6V at rest.

The new battery charges fine but the gauge jumps erratically between 40% and 70% for the first few uses — is this a calibration issue?

Yes — the fuel gauge IC on the Esprimo Mobile platform needs several full cycles to map the new cell's actual discharge curve. Until it does, the percentage estimate swings because it's still using the old cell's curve as a reference. Run two complete discharges to hibernate-cutoff followed by uninterrupted full charges. After the second cycle the gauge IC locks onto the new curve and the percentage readout stabilises.

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