Toshiba Dynabook R751 Replacement Battery PA3904U-1BRS 11.1V
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Toshiba Dynabook R751 Replacement Battery PA3904U-1BRS 11.1V - 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.
Toshiba Dynabook R751 Replacement Battery PA3904U-1BRS 11.1V - is backordered and will ship as soon as it is back in stock.
Voltage
11.1V
Amp
4400mAh
Toshiba Dynabook R751 / Satellite Pro R850 — 11.1V Li-ion Replacement Battery (PA3904U-1BRS)
This is an 11.1V, 4400mAh (48.84Wh) Li-ion battery for the Toshiba Dynabook R751, R752, R752/F, and Satellite Pro R850 series laptops. It uses OEM part numbers PA3904U-1BRS, PA3905U-1BRS, PABAS245, and PABAS246. The cell replaces a degraded or failed original pack in these thin-and-light business notebooks.
- Dynabook R751/R752 and Satellite Pro R850 compatibility: These models share the same 11.1V three-cell battery rail, connector pinout, and BMS handshake protocol — one cell fits the full platform without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Satellite Pro R850. The BMS completed full charge without tripping protection, and the system reported voltage correctly through each cycle.
- Post-install calibration on Dynabook and Satellite Pro R850: After fitting this cell, 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 these models.
BIOS reporting battery health as poor immediately after swapping the R851 or R850 cell
The Satellite Pro R850 BIOS reads health data stored in the old cell's EEPROM. When a new cell installs, that EEPROM data is blank or mismatched, so the BIOS flags the pack as degraded before it has run a single cycle. This is not a fault with the replacement cell. Run one full discharge-to-hibernate followed by an uninterrupted charge to 100% to complete the BIOS learn cycle. After that cycle, the health indicator updates to reflect actual cell capacity.
Laptop shuts down at 20–30% charge shown on Dynabook R751
This happens when the fuel gauge IC on the motherboard is still calibrated to the old, degraded cell. Under full CPU and display load, voltage drops faster than the IC expects, and the system hits its emergency cutoff threshold while the gauge still reads 20–30%. The gauge IC needs two or three full discharge-and-charge cycles against the new cell to recalibrate its voltage-to-capacity curve. After those cycles, the shutdown threshold aligns correctly with the actual remaining charge.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Toshiba
- 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 Dynabook R751 shows the new battery as 0% or "unknown" in Windows — why won't it read the charge level?
The Windows fuel gauge IC carries calibration data from the old cell, so it cannot accurately map voltage to capacity on a fresh pack straight out of the box. Run the laptop down to hibernate-cutoff on battery alone, then charge uninterrupted to 100% without unplugging. Repeat this two to three times. After those full cycles, the fuel gauge IC recalibrates its curve against the new cell and the percentage reading stabilises.
The Satellite Pro R850 BIOS shows the wrong Wh rating after I installed this cell — it says 40Wh, not 48Wh. Is the cell faulty?
The Wh figure the BIOS reads comes from rated-capacity data stored in the cell's EEPROM, not from a live measurement of the actual chemistry. The EEPROM on replacement cells is sometimes initialised to the lower-rated 40Wh value used on the standard-capacity variant. This is a data mismatch, not a physical fault — the cell itself holds the full 48.84Wh. Complete two full discharge and charge cycles and confirm charge behaviour is normal; the operating Wh in use will match the product specification.
My Dynabook R752 stops charging at around 80% and never reaches 100% — is this a cell problem?
On many Dynabook and Satellite Pro models, Toshiba's BIOS includes a charge-limit firmware setting that caps charging at 80% to reduce cell stress during long sessions on AC power. Check Toshiba System Settings or the pre-installed Toshiba eco Utility — there is a "full charge" toggle that overrides the 80% cap. Switch that setting to full charge mode, disconnect and reconnect the AC adapter, and the battery will charge through to 100%.
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