Acer Aspire One 531 Replacement Battery 11.1V 4400mAh UM09A41
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Acer Aspire One 531 Replacement Battery 11.1V 4400mAh UM09A41 - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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
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
⚠️ 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.
Acer Aspire One 531 Replacement Battery 11.1V 4400mAh UM09A41 - is backordered and will ship as soon as it is back in stock.
Voltage
11.1V
Amp
4400mAh
Acer Aspire One 531 / 751 Series — 11.1V Li-ion Replacement Battery (UM09A41)
This 11.1V, 4400mAh (48.84Wh) Li-ion battery replaces the original cell in the Acer Aspire One 531 and Aspire One 751 netbook series. It covers OEM part numbers UM09A41, UM09B7C, UM09B31, UM09B34, UM09B7D, UM09A31, UM09A71, UM09A73, UM09A75, UM09B71, and UM09B73. If your netbook no longer holds charge or shuts off unexpectedly, this is the direct cell replacement.
- Aspire One 531 and 751 platform fit: Both the 531 and 751 share the same 11.1V three-cell battery bay, connector pinout, and BMS handshake protocol — which is why a single part number covers the full range. Swapping between these models is not an issue at the hardware level.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an Aspire One 751. The BMS negotiated correctly, the BIOS accepted the cell without a fault flag, and the fuel gauge tracked state-of-charge without erratic jumps after the first calibration cycle.
- First-cycle calibration on the Aspire One: After fitting, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This forces the Aspire One's fuel gauge IC to re-learn the new cell's capacity curve and clears the false "poor battery health" warning that appears in Acer's power management after any cell swap.
BIOS reporting poor battery health immediately after fitting a new cell
The Aspire One stores battery health data in EEPROM on the old cell. When a new cell is fitted, the BIOS reads that data as missing or mismatched and flags the battery as degraded — even though the cell is new. This is a firmware artefact, not a hardware fault. Running one complete discharge-to-hibernate then a full uninterrupted charge resets the learn cycle. After two to three cycles, the BIOS health indicator will update to reflect the actual cell condition.
Netbook shuts down at 20–30% charge shown on the fuel gauge
This happens when the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The gauge shows 25% remaining, but the cell voltage has already dropped below the BMS cutoff threshold under CPU and display load — so the system shuts off without warning. It is not a faulty cell. Run two full discharge-to-hibernate cycles followed by complete charges, letting the gauge IC map the new cell's actual voltage floor. After calibration, the gauge and BMS cutoff will align — target a resting voltage of 11.1V at full charge to confirm the cell is performing correctly.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Acer
- 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
Why does my Aspire One show 0% or "unknown battery" in Windows right after fitting this replacement?
The fuel gauge IC in the Aspire One still holds EEPROM data from the old cell and treats the new one as unrecognised. Boot into Windows, let the battery discharge fully until the laptop hibernates, then charge uninterrupted to 100%. After one full cycle, the system re-reads the cell and the percentage display normalises.
The Aspire One's battery meter is jumping around — showing 60%, then 45%, then 70% within minutes. Is the cell faulty?
The fuel gauge IC needs two to three calibration cycles against the new cell before its readings stabilise. We saw the same erratic behaviour on the bench for the first cycle. Run two complete discharge-to-hibernate sequences followed by full uninterrupted charges. After that, the gauge locks onto the new cell's voltage curve and the readings settle.
Windows shows this battery as 48Wh but Acer's power manager is reporting a much lower Wh figure — why?
Acer's power manager reads the Wh rating stored in the old cell's EEPROM, which may differ from the 48.84Wh rating of this replacement cell. The discrepancy is a firmware display issue, not a capacity loss. After running the battery learn cycle — one full discharge to hibernate, then a full charge — the power manager pulls live data from the new cell and the reported Wh figure updates to match the actual cell rating.
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