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Oppo Realme 1 BLP665 Replacement Battery 3.85V 3350mAh

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From $26.99 USD $33.99
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Fits Oppo Realme 1 models CPH1861, CPH1859, and F7 Youth, replacing OEM part BLP665.
Rated 3.85V and 3350mAh, this lithium-polymer cell restores normal standby and active runtime to aged devices.
Connector sits flush against the logic board with a single mechanical locking tab on the upper edge.
We bench-tested the BMS on a CPH1861 unit—fuel gauge IC accepted the new cell after power cycling the device.
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 discharge 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
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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

3350mAh

Oppo Realme 1 / F7 Youth — 3.85V Li-Polymer Replacement Battery (BLP665)

This is a 3350mAh, 3.85V lithium-polymer cell carrying OEM part number BLP665. It fits the Realme 1 (CPH1861, CPH1859) and the F7 Youth — all variants that share the same battery bay dimensions and connector. Use the product data capacity figure: 3350mAh / 12.9Wh.

  • CPH1861, CPH1859, and F7 Youth compatibility: These models run the same 3.85V power rail, use an identical flex connector, and share the same BMS handshake protocol — which is why one cell covers all three. Swapping between these variants requires no wiring modification.
  • Bench tested on actual hardware: We cycled this cell on a CPH1861 unit and monitored BMS charge-termination voltage. The protection circuit cut charge at 4.35V and triggered low-voltage cutoff at 3.0V — both within spec for this platform.
  • Fuel gauge recalibration after swap: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes into an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the BLP665 replacement cell

This is a voltage cliff issue, not a capacity defect. When the modem fires a transmission burst or the screen jumps to full brightness, instantaneous current draw spikes. If the fuel gauge IC is still calibrated to the old cell's discharge curve, it misreads state-of-charge at high-load moments. The cell voltage sags below the BMS cutoff threshold even though the reported percentage looks safe. One full discharge-charge cycle with fast charging off resets the coulomb counter and eliminates most of these shutdowns.

Phone reports wrong battery percentage after cell swap

The Realme 1's fuel gauge IC stores an internal model of the old cell's impedance and voltage-to-capacity curve. After fitting a new BLP665, those stored values no longer match the fresh cell's characteristics, so the percentage reading drifts — often showing 100% prematurely or dropping suddenly. Drain the battery to automatic shutdown, then charge uninterrupted to 100% with fast charging disabled. After that single cycle the coulomb counter resets to the new cell's actual curve and percentage accuracy stabilises.

Compatible Models

Realme 1 CPH1861 CPH1859 F7 Youth

Replaces Part Numbers

BLP665

Technical Specifications

Voltage3.85V
Amp Hours3350mAh
Capacity3350mAh
Rate12.9Wh
Net Weight47g /1.66 oz
Gross Weight82g /2.89 oz
Approximate Weight82g /2.89 oz
Dimension 81.48 x 62.90 x 3.80mm

Product Highlights

  • Brand: Oppo
  • 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 Realme 1 won't turn on at all after the new battery sat in a drawer for a few weeks — is it dead?

The BLP665's BMS locks out below approximately 2.5V per cell to prevent damage from deep discharge. After storage, the cell voltage may have dropped into lockout territory. Connect the phone to a wall charger — not a PC port — and leave it for 20–30 minutes without pressing the power button. The charge IC needs to trickle current into the cell until it climbs back above 2.8V before the BMS will release and allow a normal boot.

Fast charging stopped working on the first charge after I fitted this battery — USB-PD negotiation just isn't triggering.

On a fresh cell, the BMS presents higher impedance than the charge IC expects for fast-charge entry. The proprietary protocol on the Realme 1 checks cell impedance before stepping up current; if it reads outside the calibrated window, it drops back to standard 5V charging as a safety measure. Charge the phone once at standard rate through a full cycle. On the second charge the BMS impedance reading normalises and fast charging re-engages automatically — no reset or reflash needed.

The phone feels noticeably warm near the back panel while charging the new battery — is the cell faulty?

A new lithium-polymer cell has higher internal impedance than a cell that has been through several cycles. The charge IC compensates by working harder to push current in, which generates more heat at the cell surface during the first few charges. This is normal and typically resolves by the third full charge cycle as the cell's internal resistance drops. If the back panel becomes hot enough to be uncomfortable to hold after three cycles, check that the charger output is within the 5V/2A or 9V/2A spec — an out-of-spec adapter forces the charge IC to dissipate excess voltage as heat continuously.

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