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Vivo B-G6 S1 Pro Replacement Battery 3.85V 4000mAh

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From $29.99 USD $36.99
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Fits Vivo S1 Pro and V1945 models, replaces OEM part number B-G6.
3.85V nominal, 4000mAh capacity — restores full charge cycles on devices showing rapid capacity loss after 500+ charge cycles.
Connector seats flat against the fuel gauge IC contact points with no locking tab — ensure clean metal-to-metal contact before closing the battery door.
We ran full discharge cycles on bench without fast charging enabled; the BMS accepted charge current cleanly and voltage held steady under sustained 500mA load.
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 high-current charging.
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

4000mAh

Vivo S1 Pro / V1945 — 3.85V Li-Polymer Replacement Battery (B-G6)

This is a 4000mAh Li-Polymer replacement battery for the Vivo S1 Pro and V1945 smartphones. It runs at 3.85V nominal and carries OEM part number B-G6. Swap it in when your original cell can no longer hold charge through a full day of use.

  • S1 Pro and V1945 compatibility: Both devices share the same board layout, connector pinout, and BMS handshake protocol — the B-G6 cell covers both without any modification.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the S1 Pro platform. The BMS accepted the cell without fault codes, and the fuel gauge IC began tracking state-of-charge after the first complete cycle.
  • First-cycle calibration tip: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Why the S1 Pro reports wrong battery percentage after a cell swap

The S1 Pro uses a coulomb counter that stores learned discharge data from the old cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry. The fuel gauge IC reads state-of-charge against stale data, so the percentage shown on screen drifts from real capacity. One full discharge — drain to automatic power-off, then charge uninterrupted to 100% — forces the IC to rewrite its reference curve against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a short high-current burst and the cell voltage drops below the BMS cutoff threshold — even though the displayed percentage looks safe. A fresh cell with an uncalibrated fuel gauge IC is especially vulnerable in the first few cycles. Run the full calibration cycle described above. After two complete cycles, the IC learns the actual voltage-to-capacity curve and the shutdowns stop. If they persist after three cycles, check that resting cell voltage reads at least 3.7V with a meter before reinstalling.

Compatible Models

S1 Pro V1945

Replaces Part Numbers

B-G6

Technical Specifications

Voltage3.85V
Amp Hours4000mAh
Capacity4000mAh
Rate15.4Wh
Net Weight60g /2.12 oz
Gross Weight160g /5.64 oz
Approximate Weight160g /5.64 oz
Dimension 83.45 x 63.30 x 4.50mm

Product Highlights

  • Brand: Vivo
  • 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

The S1 Pro screen shows 25% and the phone just shuts off — is the new battery faulty?

Not necessarily faulty. The fuel gauge IC is still calibrated to the old cell's discharge curve, so it misreads the voltage cliff on the new cell. Under modem or screen load, the cell voltage drops sharply at around 3.5V and triggers the BMS cutoff before the displayed percentage reaches zero. Run one full discharge to automatic power-off, then charge uninterrupted to 100%, and the shutdowns stop.

Fast charging stopped working after I put in the replacement cell — the phone only slow-charges now.

The S1 Pro's charge IC runs a handshake with the battery BMS before enabling high-current mode. On the first cycle with a new cell, the BMS sometimes rejects the proprietary fast-charge protocol until it has completed one standard charge. Plug in with fast charging enabled and let the phone reach 100% without unplugging — on the next charge session, fast charging should re-engage. If it doesn't, clear the battery stats cache in recovery mode and repeat.

The phone won't turn on at all after the replacement battery sat uninstalled for a few weeks — did it brick?

Li-Polymer cells self-discharge in storage, and if the cell dropped below 2.5V the BMS locks out to prevent damage. Connect the phone to its original charger and leave it for at least 30 minutes before pressing the power button — the charge IC trickle-charges the cell at a low current to bring it out of lockout. Once resting voltage recovers to 3.0V or above, the BMS releases and the phone powers on normally.

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