Asus VivoBook E502SA Compatible Battery 7.6V 4050mAh B21N1506
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Asus VivoBook E502SA Compatible Battery 7.6V 4050mAh B21N1506 - 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.
Asus VivoBook E502SA Compatible Battery 7.6V 4050mAh B21N1506 - is backordered and will ship as soon as it is back in stock.
Voltage
7.6V
Amp
4050mAh
Asus E502SA / EeeBook L502MA Series — 7.6V Li-Polymer Replacement Battery (B21N1506)
This 7.6V, 4050mAh (30.78Wh) Li-Polymer battery replaces the original cell in the Asus E502SA and EeeBook L502MA/E502MA series 15.6-inch notebooks. It fits models cross-referenced under OEM part numbers B21N1506, 0B200-01430600, 0B200-01430700, and 0B200-01430800. Install it when the original pack no longer holds a charge or when the system reports battery health as failed.
- E502SA and EeeBook L502MA platform fit: These models share the same 7.6V two-cell Li-Polymer architecture, identical connector pinout, and the same BMS handshake protocol — so one pack covers the full lineup without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an E502SA board. The BMS negotiated correctly on first connection, charge current stepped down as expected at 80%, and the fuel gauge IC accepted the new cell data without a forced reset.
- Post-swap calibration cycle for the E502SA: After installing, run the laptop down to hibernate cutoff on normal use — not by pulling the power — then charge uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the inaccurate health flag that fires after every cell replacement on this platform.
Why the E502SA shuts down at 20–30% battery shown on screen
The E502SA uses an Intel Celeron or Pentium N-series processor paired with a 1080p display — both pull hard when the CPU boosts and the backlight is at full brightness. Under that combined load, a degraded or new uncalibrated cell hits a voltage cliff before the fuel gauge reaches zero. The BIOS interprets the sudden voltage drop as a critical low and forces an immediate shutdown regardless of the percentage shown. Running the calibration cycle above lets the fuel gauge IC map the actual discharge curve of the new cell, which eliminates premature cutoffs.
BIOS shows incorrect Wh rating after fitting a new cell
The Wh figure shown in BIOS or Windows Battery Report is read from the battery's EEPROM, not measured live — it reflects the rated chemistry data written into the pack's controller chip. A new cell with a slightly different internal EEPROM revision can report a Wh value that differs from the sticker spec by a small margin. This is not a fault with the battery or the board. Confirm the actual pack voltage reads 7.6V at the connector with a multimeter, then proceed with the calibration cycle — the reported Wh figure stabilises after two to three full charge-discharge passes.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Asus
- Manufacturer: CS
- Series: Standard
- Color: Black
- Product Type: Li-Polymer
- Battery Type: Li-Polymer
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
The E502SA BIOS says "Battery Unknown" or shows 0% straight after fitting the new cell — what's causing that?
The BIOS is reading stale EEPROM data from the old cell's last known state and hasn't yet initialised the new pack. Boot into Windows, let the battery sit connected to the charger for 10 minutes, then restart. If the BIOS still shows unknown, run one full discharge to hibernate cutoff and charge uninterrupted to 100% — this forces the battery learn cycle and writes fresh calibration data to the fuel gauge IC.
The fuel gauge on my E502SA jumps around wildly — showing 60%, then 45%, then 70% within minutes of unplugging — is the battery faulty?
The fuel gauge IC on these Asus notebooks calibrates against the discharge curve of the cell it learned with. Swap in a new cell and that learned curve is wrong until the IC re-maps it. The battery itself is not faulty. Run two full discharge-to-hibernate, charge-to-100% cycles without interrupting the charge, and the gauge readings will settle to within a few percent of accurate.
New battery installed on the EeeBook L502MA but charge stops at 80% and won't go higher — is the charger the problem?
The charger is not the problem. Asus firmware on this platform includes a BIOS-level charge limit that caps charging at 80% when Battery Health Charging mode is active — it is enabled by default on some regional builds. Open MyASUS or the ASUS Battery Health Charging utility in Windows, set the mode to "Full Capacity Mode," and the charge ceiling lifts to 100% immediately without any hardware changes.
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