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Compaq 511 Replacement Battery 10.8V 4400mAh Li-ion

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From $103.99 USD $123.99
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Fits Compaq 511 and 611 notebooks; replaces OEM part numbers HSTNN-IB51, HSTNN-IB52, HSTNN-OB62, GJ655AA, and eight other Compaq battery part codes.
This 10.8V 4400mAh cell delivers 47.52Wh — matched output for full CPU and display load without voltage sag during peak drain cycles.
Connector seats into the Compaq battery slot with a spring latch; orientation is keyed to prevent reverse insertion on the motherboard contact plate.
We bench-tested the BMS through three full discharge-to-cutoff cycles; the fuel gauge IC settled into accurate reporting by cycle two with stable voltage curve.
After installation, run one full discharge to hibernation cutoff, then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears the false poor-health warning that appears 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.

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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.

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🔹 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

10.8V

Amp

4400mAh

Compaq 511 / 611 — 10.8V Li-ion Replacement Battery (HSTNN-IB51)

This is a 10.8V, 4400mAh Li-ion replacement battery for the Compaq 511 and 611 notebooks. It slots into the standard battery bay and connects via the original multi-pin dock connector. OEM part numbers include HSTNN-IB51, HSTNN-IB52, HSTNN-XB51, and 451085-141, among others listed above.

  • 511 and 611 shared platform: Both models run the same voltage rail, use the same physical bay dimensions, and share the same BMS handshake protocol — which is why a single cell pack covers both. The connector pinout and charge termination logic are identical across the two.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a 511 unit. The BMS negotiated charge correctly, cell temperature stayed within spec, and the OS fuel gauge registered the full rated capacity after two calibration cycles.
  • First-use discharge cycle on the 511: After installing, run the laptop on battery until it hibernates at cutoff — then charge uninterrupted to 100%. This forces the BIOS to run a learn cycle against the new cell and clears the inaccurate battery health warning that appears after every cell swap.

Why the 511 shuts down between 20–30% after a battery swap

The 511's BIOS tracks cell voltage curves from the previous battery. After a swap, it uses the old voltage map to predict remaining charge — and gets it wrong. Under full CPU and display load, the new cell's actual voltage drops faster than the BIOS expects at that state of charge, triggering an emergency cutoff. Running two full discharge-to-hibernate cycles recalibrates the fuel gauge IC against the new cell chemistry and stops the premature shutdown.

BIOS reporting battery health as "poor" or "replace" immediately after fitting a new cell

This is an EEPROM data mismatch, not a cell defect. The BIOS reads health status from stored cycle count and capacity data written by the previous battery's controller — the new cell arrives with different EEPROM values, which the BIOS flags as degraded. Run the battery learn cycle: discharge fully to hibernate cutoff, then charge to 100% without interruption. After one complete cycle, the BIOS rewrites its health reference and the warning clears.

Compatible Models

511 611

Replaces Part Numbers

451085-141 451086-121 451086-161 451568-001 GJ655AA HSTNN-IB51 HSTNN-IB52 451085-141 451086-121 451086-161 456864-001 464119-361 484787-001 GJ655AAA HSTNN-IB62 HSTNN-OB62 HSTNN-XB51 HSTNN-XB52 HSTNN-XB62 KU532AA

Technical Specifications

Voltage10.8V
Amp Hours4400mAh
Capacity4400mAh
Rate47.52Wh
Net Weight338.2g /11.93 oz
Gross Weight608.2g /21.45 oz
Approximate Weight608.2g /21.45 oz
Dimension 268.28 x 61.11 x 21.50mm

Product Highlights

  • Brand: Compaq
  • 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 Compaq 511 shows the new battery as 0% and won't read it at all — is the cell dead out of the box?

It's not a dead cell — it's the fuel gauge IC starting from an uncalibrated state with no reference data for the new chemistry. The BIOS has no valid charge curve to read against yet. Plug in the AC adapter and leave it charging uninterrupted for a full cycle; the gauge IC needs at least one complete charge from near-zero to 100% before it reports accurately. After that first uninterrupted charge, the percentage will populate correctly.

The Compaq 511 charges the new battery to 80% then stops — it won't go higher no matter how long it's plugged in.

This is a BIOS-controlled charge threshold, not a fault with the cell. Some 511 BIOS versions enable a charge limit by default to reduce cell wear — it caps termination voltage at roughly 80% of full capacity. Go into the BIOS setup (F10 at POST) and check the Power Management section for a "Battery Charge Mode" or "Extended Life" setting; disable it or switch to "Full Charge." The cell will then charge to 100% on the next cycle.

System information on my 511 shows this battery as 40Wh — but the product says 47.52Wh. Which is right?

The system info figure comes from the EEPROM on the battery controller, which stores the rated Wh value written at manufacture — this can differ from the actual measured capacity of the cells inside. The 47.52Wh figure in the product data reflects the actual cell chemistry at 10.8V × 4400mAh. After two full calibration cycles, the OS fuel gauge will align closer to the real capacity; the EEPROM-reported Wh value in system info may still read lower, but that does not affect how the battery charges or discharges.

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