Welcome to our store. Your trusted source for batteries and power solutions. Learn more

For support or quotes: sales@batteryweb.com
WELCOME5
BatteryWeb

Neffos X20 Compatible Battery 3.85V 3900mAh NBL-43A4000

Up to 21% off
New arrival
From $26.99 USD $33.99
Shipping calculated at checkout.
Fits Neffos X20, X20 Pro, TP7071, TP9131A — replaces OEM battery NBL-43A4000.
This 3.85V, 3900mAh Li-Polymer cell restores full charge capacity to the X20 after original degradation or failure.
Connector slides straight into the battery slot with no locking tab — orientation marked on the cell housing.
We ran full discharge cycles on the X20 platform — BMS accepted the new cell without fault codes or cutoff errors.
On first use after installation, disable fast charging for one complete discharge-charge cycle to let the fuel gauge IC recalibrate against the new cell curve.
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
WECARE5

Please Confirm Delivery Timeline

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
4.8
★★★★★
★★★★★
Average Customer Rating
By continuing with your purchase, you acknowledge and agree to the estimated 7–10 business day delivery timeframe.
Visa Mastercard American Express PayPal Apple Pay Google Pay Shop Pay Discover Klarna Afterpay Stripe
✦

Check that your old battery model number and device model to match our description. This makes sure they work together.

✦

We ship your order same day if you buy it before 4 PM EST.

Warranty

Let customers speak for us

from 11 reviews

Product is exactly as described and arrived quickly

Robert Jones
Rocket ES4-12 Compatible Replacement Battery

It took a bit longer than expected, likely due to the holiday season, but that was understandable. So far, the battery seems to be working well!

Linda M.
MGE UPS Systems Pulsar EX 1500RT Compatible Replacement Battery By Bright Way

Excellent substitute for the original, appearing to be the perfect replacement.

Alberto J.
APC SMART-UPS RT SURTA3000RMXL3U UPS High Performance Replacement Battery Set

It was what i was looking for. Support is fast

Jaswal
WAHEGURUG - RADHASWAMI

Fast service

Mark Casias
BatteryWeb

Perfect fit

Mark Casias
STX20L-BS Battery for Harley Softail FLS FLST 1991-2017 High Performance

Works Perfectly!!

Ben Benson
Invacare 220 Scooter High Performance Medical Replacement Battery Set

Send Your Battery Photo

Expert Technician Help

Snap a photo or video of your battery and send it to us. We'll identify the exact replacement—fast and hassle-free. Our team has helped thousands of customers find the right battery quickly and easily.

POST YOUR BATTERY IMAGE
Product & Solutions Expert

Product & Solutions Expert

✉ sales@batteryweb.com

🔹 10+ Years Battery Experience 🔹 Fast & Accurate Identification

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

3900mAh

Neffos X20 / X20 Pro Series — 3.85V Li-Polymer Replacement Battery (NBL-43A4000)

This is a 3.85V, 3900mAh Li-Polymer cell that replaces part number NBL-43A4000 in the Neffos X20, X20 Pro, TP7071, and TP9131A smartphones. The original cell degrades through charge cycles and loses the ability to hold voltage under load, cutting the phone off before the display reads zero. This replacement restores full charge capacity to the stock specification.

  • X20 and X20 Pro compatibility: Both the X20 (TP7071) and X20 Pro (TP9131A) share the NBL-43A4000 cell footprint, voltage rail, and BMS connector pinout. Swapping between variants does not require firmware changes or connector adapters.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the X20 platform and confirmed BMS handshake, charge acceptance, and voltage delivery under screen-on and modem-active loads. No fault flags triggered during testing.
  • First-cycle fast charge caution: After installation, disable fast charging for one full discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell, which can cause erratic percentage readings early on.

Why the X20 reports wrong battery percentage after a cell swap

The X20 uses a fuel gauge IC that learns a cell's discharge curve over cycles. When you install a new cell, the IC still holds the old cell's calibration data. It maps voltage readings to percentage estimates based on a worn curve, so the numbers it reports can be off by 10–20% until it relearns. One full discharge to auto-off followed by a complete charge cycle resets the coulomb counter and lets the IC build an accurate model of the new cell.

Sudden shutdown at 20–30% charge on the replacement cell

This happens when the fuel gauge IC is still calibrated to the old cell and reads the voltage incorrectly under load. A fresh Li-Polymer cell has a steeper voltage cliff than a degraded one — under modem or screen load, voltage drops fast enough to trigger low-voltage protection before the display percentage catches up. The fix is one full calibration cycle: drain the phone until it shuts itself off, then charge uninterrupted to 100% without fast charge enabled. After that cycle, the IC recalibrates and shutdown behaviour normalises above 3.4V per cell.

Compatible Models

X20 X20 Pro TP7071 TP9131A

Replaces Part Numbers

NBL-43A4000

Technical Specifications

Voltage3.85V
Amp Hours3900mAh
Capacity3900mAh
Rate15.02Wh
Net Weight55g /1.94 oz
Gross Weight105g /3.70 oz
Approximate Weight105g /3.70 oz
Dimension 85.30 x 62.60 x 4.30mm

Product Highlights

  • Brand: Neffos
  • 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

My Neffos X20 won't turn on at all after sitting in a drawer for months — is the new battery dead on arrival?

It is almost certainly not dead. If the original cell drained below roughly 2.5V during storage, the BMS enters a lockout state to prevent damage and will not respond to a normal charge attempt. Plug the phone into a 5V charger and leave it for 20–30 minutes without pressing the power button — the charge IC needs to trickle current into the cell to bring it above the BMS recovery threshold before the phone will boot. If the phone still does not respond, try a different USB cable and confirm the charger outputs at least 1A.

Fast charging stopped working after I swapped the battery on my X20 — the phone only charges slowly now.

This is normal on the first cycle after a cell replacement. The BMS on a new cell has not yet completed a handshake with the phone's charge IC, so the phone defaults to standard 5V charging as a safety fallback. Run one full discharge-to-shutdown cycle followed by a full charge, then reconnect the fast charger. After that initial cycle the charge IC recognises the new cell's parameters and fast charge resumes at the correct current.

The battery percentage on my X20 jumps around — it drops from 45% to 12% in a few minutes then jumps back up.

The fuel gauge IC is recalibrating against the new cell's discharge curve and hasn't built an accurate voltage-to-percentage map yet. The IC was calibrated to the worn cell it replaced, so voltage readings from the fresh cell translate to incorrect percentages. Drain the phone completely until it powers itself off, then charge it in one uninterrupted session to 100% with fast charging disabled. That single full cycle resets the coulomb counter and the percentage readout stabilises.

Payment & Security

Payment methods

  • American Express
  • Apple Pay
  • Bancontact
  • Diners Club
  • Discover
  • Google Pay
  • Mastercard
  • PayPal
  • Shop Pay
  • Visa

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

Related Products

TP-Link Neffos X20 Replacement Battery, 3.85V, 3900mAh, Li-Polymer 1

Engineered for Performance. Built to Last.

Check out our top-rated selection of reliable products built to last. We offer high-quality options that deliver consistent performance for all your needs.

Our Collections