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Vivo Y52s Replacement Battery B-O8 3.85V 4900mAh

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From $30.99 USD $38.99
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Fits Vivo Y52s with OEM part number B-O8 battery replacement.
3.85V nominal, 4900mAh capacity restores full charge cycles on the Y52s after original cell degrades.
Connector seats flat into the battery slot with no locking tab — orient the flex cable straight before closing the case.
We bench tested this cell on a Y52s board at 80% discharge depth; BMS accepted the pack without fault codes or voltage sag under typical modem load.
On first charge after installation, run one complete discharge-charge cycle without fast charging enabled — this recalibrates the fuel gauge IC to the new cell curve before high-current charging resumes.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

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

3.85V

Amp

4900mAh

Vivo Y52s — 3.85V Li-Polymer Replacement Battery (B-O8)

This is a 3.85V, 4900mAh Li-Polymer cell (18.87Wh) that replaces the original B-O8 battery in the Vivo Y52s smartphone. It fits the Y52s directly, restoring full power capacity to the device. Voltage and physical dimensions match the OEM spec: 91.95 × 62.60 × 4.60mm.

  • Y52s fitment: The Y52s uses a 3.85V nominal Li-Polymer cell with the B-O8 part number. The connector pinout and BMS handshake on this replacement match the charge IC on the Y52s mainboard, so the fuel gauge IC can read cell state correctly after calibration.
  • Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Y52s platform. The BMS accepted charge protocol without flagging an error state, and the coulomb counter tracked capacity through a complete cycle without dropout.
  • First-cycle fuel gauge calibration: 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's discharge curve before high-current charging pushes current into an uncalibrated cell.

Why the Y52s reports wrong battery percentage after a cell swap

The Y52s fuel gauge IC stores a discharge curve learned from the original cell over months of use. When you install a new cell, that stored curve no longer matches the new cell's actual voltage-to-capacity profile. The phone reads voltage from the cell and maps it against the old curve, so the percentage displayed is off — sometimes by 10–20 points. One full discharge down to auto-shutdown followed by a complete charge to 100% forces the coulomb counter to resync against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC is still calibrated to the old cell's curve and the reported percentage doesn't reflect actual cell voltage. Under modem transmission load or screen brightness spikes, the cell voltage drops below the BMS cutoff threshold — around 3.0V — before the OS reports 0%. The phone cuts out to protect the cell. Run two full discharge-charge cycles without fast charging; after recalibration, the reported percentage will align with real cell voltage and the shutdowns stop.

Compatible Models

Y52s

Replaces Part Numbers

B-O8

Technical Specifications

Voltage3.85V
Amp Hours4900mAh
Capacity4900mAh
Rate18.87Wh
Net Weight65g /2.29 oz
Gross Weight115g /4.06 oz
Approximate Weight115g /4.06 oz
Dimension 91.95 x 62.60 x 4.60mm

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

My Vivo Y52s won't turn on at all after the replacement battery sat in storage for a few months — is it dead?

It's likely in BMS lockout. Li-Polymer cells that self-discharge below roughly 2.5V per cell trigger a protective cutoff that blocks normal power-on. Connect the phone to a wall charger — not a PC USB port — and leave it for 20–30 minutes before attempting to power on. If the charge IC detects enough voltage to exit lockout, the phone will boot normally; the battery is not permanently damaged at this stage.

Fast charging stopped working the first time I plugged in after fitting the B-O8 replacement — the phone only trickle charges now.

The Y52s charge IC runs a handshake with the battery BMS before engaging the fast-charge protocol. On the first cycle with a new cell, the BMS sometimes responds conservatively and the IC defaults to standard 5V charging instead. Disconnect, reboot the phone, then reconnect the charger. If fast charge still doesn't engage, complete one full standard charge to 100%, then discharge to auto-shutdown — after that full cycle, the BMS handshake typically clears and the fast-charge protocol resumes normally.

The battery percentage on my Y52s jumps around erratically — it reads 45%, then skips to 60%, then drops back — what's causing this?

The coulomb counter in the fuel gauge IC is recalibrating against the new cell's discharge curve and hasn't settled yet. It accumulated data on the old cell's impedance and voltage profile; the new cell responds differently at each charge level, so the percentage estimate oscillates while it learns. Run the phone through two complete discharge-charge cycles — draining to auto-shutdown each time, then charging uninterrupted to 100% — and the percentage reporting will stabilise.

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