About this replacement
BlackView BV9700 — 3.85V Li-Polymer Replacement Battery (V605872P)
This is a 3.85V, 4000mAh Li-Polymer replacement cell for the BlackView BV9700 rugged smartphone. It matches the OEM part number V605872P and fits directly into the BV9700 battery bay. Swap it when your original cell no longer holds charge through a normal day of use.
- BV9700 fitment: The BV9700 uses a sealed, proprietary bay with a flex connector keyed to this cell geometry — 71.70 × 58.40 × 6.20mm. The BMS on this replacement communicates with the phone's charge IC using the same handshake protocol as the factory cell, so the fuel gauge and protection circuits initialise correctly on first boot.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the BV9700 platform. The BMS held the charge termination voltage correctly, and thermal monitoring stayed within spec across repeated charge cycles. No false cutoffs were triggered at low state of charge.
- First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. The fuel gauge IC needs to map its coulomb counter against the new cell's discharge curve before fast charge pushes high current into an uncalibrated cell.
Sudden shutdown at 20–30% on the BV9700 after a cell swap
This happens because the fuel gauge IC is still running the discharge curve it learned from the old, degraded cell. When a fresh cell hits a voltage point that the old curve mapped to 20%, the IC thinks it's near-empty and signals a shutdown — even though the new cell has capacity left. The fix is one full slow discharge to around 3.4V per cell, followed by a full slow charge. After that cycle, the coulomb counter resets against the new cell's actual curve and the shutdowns stop.
USB fast charging not activating on the first cycle after replacement
The BV9700's charge IC applies a pre-charge trickle current to any new cell it doesn't recognise from previous sessions — this is normal BMS behaviour on first contact. Fast charge protocol negotiation via USB-PD is gated until the cell voltage climbs above 3.6V and the IC confirms the BMS handshake is stable. Plug into a standard 5V charger for the first full cycle. Once the cell reaches a full charge at standard rate, fast charging activates on the next session without any further steps.