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Lenovo Z5 Pro JR40 Compatible Battery 3.85V 3100mAh

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From $26.99 USD $33.99
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Fits Lenovo Z5 Pro with OEM part number JR40.
3.85V, 3100mAh lithium-polymer cell powers the processor, display, and modem at rated voltage without sag.
Connector slides into the battery slot with flat orientation; locking tab seats flush against the housing clip.
We bench-tested this JR40 cell in a Z5 Pro unit; the BMS accepted the new pack on first insertion with no fault codes.
On first use after installation, disable fast charging for one complete discharge-charge cycle — this lets the fuel gauge IC recalibrate against the new cell discharge curve before USB-PD pushes current into an uncalibrated cell.
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.

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.

Voltage

3.85V

Amp

3100mAh

Lenovo Z5 Pro (L78031 / L78032) — 3.85V Li-Polymer Replacement Battery (JR40)

This is a 3.85V, 3100mAh Li-Polymer replacement battery for the Lenovo Z5 Pro smartphone (model numbers L78031 and L78032). It carries OEM part number JR40 and slots into the same physical bay as the original cell. Voltage, capacity, and connector position match the factory specification.

  • L78031 and L78032 compatibility: Both Z5 Pro variants share the same battery bay geometry, connector pinout, and BMS handshake protocol — one JR40 cell covers both boards without modification.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the Z5 Pro board. The BMS accepted the cell, charge IC ramped normally, and protection cutoffs triggered at expected voltage thresholds on both ends of the curve.
  • First-cycle fast charge hold-off: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC build an accurate discharge curve for the new cell before high-current charging pushes into an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the Z5 Pro after a cell swap

The Z5 Pro's fuel gauge IC retains the discharge curve of the old, degraded cell in its coulomb counter. When a fresh cell is installed, the IC's internal map no longer matches the new cell's actual voltage curve. Under high load — modem transmit bursts or screen-on peaks — the new cell's voltage briefly sags below the threshold the IC expects at that reported percentage, triggering an emergency shutdown. One full discharge-charge cycle at standard current resets the calibration and eliminates the early cutoff.

Phone won't power on after the JR40 replacement sat in storage

Li-Polymer cells self-discharge during storage. If the replacement cell drops below approximately 2.5V before installation, the BMS enters lockout mode to prevent damage and will refuse to pass current to the board. The phone shows no response — no charging indicator, no boot attempt. Connect a charger and leave it for 15–20 minutes without pressing the power button; the charge IC will trickle current into the cell until voltage climbs above the BMS re-enable threshold, typically around 2.8–3.0V, after which normal charging resumes.

Compatible Models

Z5 Pro L78031 L78032

Replaces Part Numbers

JR40

Technical Specifications

Voltage3.85V
Amp Hours3100mAh
Capacity3100mAh
Rate11.94Wh
Net Weight43.8g /1.55 oz
Gross Weight93.8g /3.31 oz
Approximate Weight93.8g /3.31 oz
Dimension 85.20 x 50.60 x 4.30mm

Product Highlights

  • Brand: Lenovo
  • Manufacturer: CS
  • Series: X-Longer
  • Color: Black
  • Product Type: Li-Polymer
  • Battery Type: Li-Polymer
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Z5 Pro shuts off at around 25% after I put in the new JR40 battery — is the replacement faulty?

The cell itself is not the problem. The fuel gauge IC on the Z5 Pro board is still reading from the discharge curve it mapped to your old, worn cell. When the new cell's voltage sags briefly under modem or display load, the IC interprets it as a near-empty pack and cuts power. Run one full discharge down to automatic shutdown, then charge uninterrupted to 100% at standard (non-fast) charge speed. After that single calibration cycle, early shutoffs stop.

The Z5 Pro shows erratic percentages — jumping from 60% to 40% and back — right after swapping the battery.

This is the coulomb counter recalibrating against the new cell's actual charge curve. The IC accumulated error tracking the old cell over hundreds of cycles, and those figures do not map cleanly onto the fresh JR40's voltage profile. Percentage readings stabilise after two to three full discharge-charge cycles at standard rate. Do not interrupt the cycles — partial charges extend the recalibration time.

Fast charging stopped working on the Z5 Pro after I installed the replacement battery.

On the first cycle after a cell swap, the charge IC on some Z5 Pro units rejects the fast-charge handshake until it confirms the new cell's internal resistance is within an acceptable range. This is a BMS protection behaviour, not a fault with the replacement. Charge the phone once at standard speed to completion, then disconnect and reconnect the charger — the fast-charge protocol should negotiate normally from the second session onward. If it does not, check that the battery connector is fully seated, as a partial connection raises measured impedance above the threshold the IC uses to approve high-current charging.

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