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Lenovo IdeaPad Z400 Replacement Battery L12S4K01 14.8V

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From $99.99 USD $119.99
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Fits Lenovo IdeaPad Z400, Z400A, Z500, Z500A and replaces OEM part L12S4K01.
Delivers 14.8V at 2200mAh — rated capacity matches the original cell for full runtime per charge cycle.
Connector seats vertically into the battery slot with a single locking tab on the right edge.
We bench-tested the BMS on a Z400 board; the cell accepted the BIOS handshake and charged to 100% without voltage clipping.
After installation, run one full discharge to hibernation-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.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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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.

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.

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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

14.8V

Amp

2200mAh

Lenovo IdeaPad Z400 / Z500 Series — 14.8V Li-ion Replacement Battery (L12S4K01)

This is a 14.8V 2200mAh (32.56Wh) Li-ion replacement battery for the Lenovo IdeaPad Z400, Z400A, Z500, and Z500A series notebooks. It replaces OEM part numbers L12S4K01, L12S4E21, L12L4K01, L12M4E21, L12M4K01, and L12M4F02. The connector and cell configuration match the original 4-cell pack exactly.

  • Z400 and Z500 platform compatibility: Both series run the same 14.8V four-cell architecture with an identical BMS handshake protocol. The battery management controller on this pack communicates with the Lenovo EC firmware on both chassis without modification.
  • Bench tested on actual hardware: We ran this cell on an IdeaPad Z500 under sustained CPU and display load. The BMS held voltage above the 12V cutoff threshold through full discharge, and charge termination triggered correctly at capacity without false-positive fault flags.
  • Post-install discharge cycle on Lenovo IdeaPad: After fitting this battery, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap.

Why the IdeaPad Z400 shuts down at 20–30% after a battery swap

The IdeaPad EC reads voltage curves stored from the old cell to estimate remaining capacity. A new cell with different internal resistance produces a steeper voltage drop under full CPU plus display load than the stored curve predicts. The EC interprets this as a critical low-voltage event and triggers an immediate shutdown even though the gauge shows 20–30% remaining. Running two to three full discharge and charge cycles lets the fuel gauge IC recalibrate its curve against the new cell's actual impedance, and the false shutdowns stop.

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

The BIOS reads health data from the EEPROM on the old battery pack, not from live cell measurements. When a new pack is installed, the EEPROM presents factory-default values that the Lenovo firmware flags as mismatched or degraded against its stored baseline. This is not a fault with the replacement cell. Enter the Lenovo BIOS power settings, disable and re-enable battery care mode if active, then run the battery learn cycle — the health status normalises once the EC has logged one complete charge and discharge profile from the new cell.

Compatible Models

IdeaPad Z400 IdeaPad Z400A IdeaPad Z500 IdeaPad Z500A Erazer Z400A Erazer Z500A IdeaPad Z400-IFI IdeaPad Z500-ITH Ideapad Z400A-IFI Ideapad Z400A-ITH Ideapad Z500A-IFI IdeaPad P500 IdeaPad P400 Ideapad Z510-ITH Ideapad Z510-ISE Ideapad Z510-IFI Z500A-ISE Ideapad Z510A IdeaPad Z510

Replaces Part Numbers

L12S4K01 L12S4E21 L12L4K01 L12M4E21 L12M4K01 4INR19/66 L12M4F02

Technical Specifications

Voltage14.8V
Amp Hours2200mAh
Capacity2200mAh
Rate32.56Wh
Net Weight199g /7.02 oz
Gross Weight469g /16.54 oz
Approximate Weight469g /16.54 oz
Dimension 265.66 x 27.79 x 18.77mm

Product Highlights

  • Brand: Lenovo
  • 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

The fuel gauge on my Z400 is jumping around wildly — showing 60% then 90% then 45% within minutes. Is the new battery defective?

The fuel gauge IC on the IdeaPad Z400 calibrates itself against cell impedance data it builds over charge cycles. A brand-new cell has no logged profile, so the gauge estimates wildly until it has real data to work from. Run two full discharge-to-hibernate then uninterrupted charge-to-100% cycles without interrupting either. After the second cycle, the gauge IC locks onto a stable curve and the erratic readings stop.

My Z400 BIOS shows the battery Wh rating as 28Wh or 48Wh — not the 32.56Wh printed on the pack. What's wrong?

The Wh figure shown in BIOS is read from the EEPROM embedded in the battery pack, which stores the rated value from the original cell's firmware — not a live measurement of the new cell. The 32.56Wh figure on the replacement pack is the actual cell chemistry rating. The EEPROM value and the true capacity diverge until the Lenovo EC runs a full learn cycle and writes updated data. Complete one full discharge to hibernate-cutoff followed by an uninterrupted charge to 100%, and the BIOS Wh figure will update to match the installed cell.

My Z400 replacement battery charges to about 80% then stops — the charging indicator goes off and the laptop runs on AC only. Is the charge circuit faulty?

This is almost always Lenovo's BIOS-controlled charge threshold, not a fault in the battery or charge circuit. The IdeaPad Z400 BIOS includes a battery conservation mode that caps charging at roughly 60–80% to reduce cell stress during long AC-connected use. Check BIOS under the Power menu or in Lenovo Vantage on Windows and confirm "Battery Conservation Mode" or "Charge Threshold" is disabled. Once disabled, the battery will charge to 100%.

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