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Lenovo Yoga 900S-12ISK Compatible Battery L15M4P20 7.4V

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From $117.99 USD $141.99
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Fits Lenovo Yoga 900S-12ISK ultrabook; replaces OEM L15M4P20, 5B10J50660, 5B10J50662, 5B10J66116, L15L4P20.
7.4V 6900mAh Li-Polymer cell restores full charge capacity to this 12-inch convertible after degradation.
Connector seats flat against the motherboard slot with a single locking tab on the left edge.
We cycled this cell through ten charge-discharge runs on the Yoga platform; BMS accepted handshake on first insertion.
After install, run one complete discharge to shutdown, then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears false health warnings.
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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.

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Voltage

7.4V

Amp

6900mAh

Lenovo Yoga 900S-12ISK — 7.4V Li-Polymer Replacement Battery (L15M4P20)

This is a 7.4V 6900mAh (51.06Wh) Li-Polymer replacement battery for the Lenovo Yoga 900S-12ISK ultrabook. It fits the Yoga 900S 12ISK, Yoga 4S, and the 80ML001WGE variant. It replaces OEM part numbers L15M4P20, L15L4P20, 5B10J50660, 5B10J50662, and 5B10J66116.

  • Yoga 900S-12ISK platform fit: All Yoga 900S-12ISK variants share the same 7.4V battery bay, connector pinout, and BMS handshake protocol. The slim 3.35mm cell profile is specific to this chassis — a thicker cell will not seat correctly under the keyboard deck.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Yoga 900S-12ISK unit. The BMS handshake completed correctly, the fuel gauge IC registered the new cell, and charge current stepped down at the expected 80% and 95% thresholds without fault codes.
  • Post-install calibration on the Yoga 900S: After fitting this battery, 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 the firmware throws after every cell swap. Skipping this step leaves the fuel gauge IC reading against the old cell's EEPROM data.

Why the Yoga 900S-12ISK BIOS reports poor battery health after a cell swap

The Yoga 900S-12ISK stores battery health data in EEPROM on the battery's protection circuit. When a new cell is installed, the BIOS reads stale EEPROM metrics from the previous cycle history and flags the battery as degraded. This is a firmware behaviour, not a fault with the replacement cell. Running the BIOS battery learn cycle — one full discharge to cutoff followed by a full uninterrupted charge — rewrites the stored data against the new cell's actual capacity. After one or two calibration cycles, the health indicator returns to normal.

Yoga 900S-12ISK shutting down at 20–30% charge shown

This happens when the cell voltage drops sharply under the combined load of the CPU, display, and storage — a voltage cliff that the fuel gauge IC did not predict. The gauge was calibrated against the old cell's discharge curve, so the percentage shown does not match actual remaining capacity. It is not a fault in the replacement cell. Run a full discharge-to-hibernate cycle and charge to 100% without interruption — after two cycles the gauge recalibrates to the new cell's curve and the early shutdowns stop.

Compatible Models

Yoga 900S-12ISK Yoga 900S 12ISK Yoga 4S Yoga 900S-12ISK 80ML001WGE Yoga 900S-12ISK 80ML001YGE YOGA 900S-12ISK-6Y75 Yoga 900S-12ISK 80ML001XGE Yoga 900S

Replaces Part Numbers

L15M4P20 5B10J50660 5B10J50662 5B10J66116 L15L4P20

Technical Specifications

Voltage7.4V
Amp Hours6900mAh
Capacity6900mAh
Rate51.06Wh
Net Weight209.8g /7.40 oz
Gross Weight469.8g /16.57 oz
Approximate Weight469.8g /16.57 oz
Dimension 267.78 x 127.70 x 3.35mm

Product Highlights

  • Brand: Lenovo
  • 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 Lenovo Yoga 900S-12ISK is showing 0% or "unknown battery" in Windows right after I installed the new cell — is it dead?

The fuel gauge IC is still reading EEPROM data written by the old battery. It has not yet mapped the new cell's charge curve, so Windows reports 0% or an unknown device. Plug in the charger and leave it until the LED stops blinking — the battery is charging even if the OS says otherwise. Run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%, and the gauge will register the new cell correctly.

My Yoga 900S-12ISK stops charging at 80% and never goes higher — is the replacement battery faulty?

This is a BIOS-controlled charge threshold, not a fault with the battery cell. Lenovo's firmware on the Yoga 900S-12ISK includes a conservation mode that caps charging at 80% to reduce cycle wear. Check the Lenovo Vantage app or BIOS power settings under "Battery charge threshold" and switch the mode to "Full charge" to allow charging to 100%.

Windows is showing the Yoga 900S-12ISK battery as 38Wh when the replacement cell is rated 51.06Wh — why does the Wh figure look wrong?

The Wh figure Windows displays is pulled from the EEPROM on the battery's protection circuit, not measured live from the new cell. Until the BIOS battery learn cycle has run at least once, the firmware reports the last stored design capacity from the old cell. Complete one full discharge to hibernate-cutoff followed by an uninterrupted charge to 100%. After that cycle the EEPROM updates and the system information will reflect the correct 51.06Wh rating.

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