BLP765 Oppo A91 Replacement Battery 3.85V 3800mAh
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BLP765 Oppo A91 Replacement Battery 3.85V 3800mAh - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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
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
⚠️ 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.
BLP765 Oppo A91 Replacement Battery 3.85V 3800mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.85V
Amp
3800mAh
Oppo A91 / F15 2020 — 3.85V Li-Polymer Replacement Battery (BLP765)
This is a 3800mAh Li-Polymer cell at 3.85V, built to the BLP765 specification. It fits the Oppo A91, F15 2020, PCPM00, and CPH2001 variants. Swap it in when the original cell no longer holds a usable charge across a full day.
- A91 / F15 2020 platform fit: These four model codes — A91, PCPM00, F15 2020, CPH2001 — share the same mainboard layout, connector pinout, and BMS handshake protocol, which is why a single BLP765 cell covers all of them without modification.
- Bench tested on actual hardware: We ran the BLP765 through charge and discharge cycles on the CPH2001 board. The BMS accepted the cell on first connection, charge termination fired correctly at 4.35V, and the fuel gauge IC initialised without error flags.
- Fuel gauge recalibration on first use: After installation, disable VOOC fast charging for one complete discharge-to-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins on an uncalibrated cell.
Sudden shutdown at 20–30% on the A91 after a cell swap
This happens when the fuel gauge IC is still using the discharge curve from the old, degraded cell. The new cell has a steeper voltage cliff under modem and display load than the IC expects, so it reads 25% right up until the cell voltage drops below the shutdown threshold. The fix is a full manual calibration cycle — drain the phone until it powers off, then charge uninterrupted to 100% without using the phone. After one clean cycle, the coulomb counter resets to the new cell's actual capacity and the early shutdown stops.
VOOC fast charging not engaging after BLP765 installation
On the first charge cycle after a cell swap, the charge IC on the A91 runs a handshake verification before it allows VOOC current. If the BMS on the replacement cell has not yet completed its initialisation sequence, the IC falls back to standard 5V charging as a precaution. Plug into a VOOC-compatible charger and let the first full charge run without interruption — do not unplug partway through. By the second cycle, the handshake completes and VOOC engages normally.
Compatible Models
Replaces Part Numbers
Technical Specifications
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 Oppo A91 won't turn on at all after the replacement battery sat in a drawer for a few months — is the cell dead?
The BMS locks out below roughly 2.5V per cell to prevent damage, and a battery in storage can drop below that threshold. Plug the phone into a wall charger — not a PC USB port — and leave it for 20 to 30 minutes before attempting to power on. If the BMS recovers, the charge IC will trickle current into the cell until it clears the lockout threshold, after which normal charging resumes and the phone boots.
The battery percentage on my A91 jumps around erratically — it drops from 60% to 30% in minutes, then bounces back.
The fuel gauge IC stores a discharge model calibrated to the original cell's impedance profile. A new BLP765 cell has different internal resistance characteristics, so the IC's coulomb counter loses accuracy under variable loads like the modem switching between bands. Run one full uninterrupted cycle — discharge until automatic shutdown, then charge to 100% without unplugging — and the IC will recalculate its model against the new cell. Erratic jumps typically settle after that single calibration cycle.
The phone feels warm near the battery area during the first few charges after fitting the BLP765 — is something wrong?
Mild warmth on the first few cycles is normal with a new high-impedance cell. A fresh Li-Polymer cell has slightly higher internal resistance than a broken-in one, so the charge IC dissipates a small amount of extra heat as current pushes into it. Keep the phone out of a case for the first two or three charging sessions so heat can dissipate freely. If the back becomes hot to the touch — not just warm — disconnect the charger and check that the connector is fully seated flat against the board.
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