Crosscall Shark-V2 Replacement Battery BL-651A 3.7V 1200mAh

Crosscall Shark-V2 — 3.7V Li-ion Replacement Battery (BL-651A)

This is a 3.7V, 1200mAh Li-ion cell for the Crosscall Shark-V2 rugged smartphone. It replaces OEM part BL-651A when the original cell's capacity has degraded. Dimensions are 58.70 × 39.90 × 7.20mm — confirm these against your existing cell before ordering.

• Shark-V2 fitment: The Shark-V2 uses a compact removable cell at 3.7V nominal. This replacement matches that voltage rail and physical footprint, so the BMS handshake completes on power-up without fault codes.
• Bench tested on actual hardware: We cycled this cell through charge and discharge under screen-on and modem-active loads. The BMS held cutoff thresholds correctly and did not trigger premature low-voltage shutoff during the test runs.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins against an uncalibrated reference.

Sudden shutdown at 20–30% on the Shark-V2 after a cell swap

This is a voltage cliff issue, not a capacity fault. When the modem or display draws peak current, a new cell with an uncalibrated fuel gauge IC can drop below the BMS cutoff threshold before the percentage readout reaches zero. The phone shuts down because real cell voltage has collapsed under load, even though the reported percentage looks safe. Run one full discharge to near 0% and a full charge to 100% to let the coulomb counter re-anchor its calibration.

Phone feels warm near the battery during the first charge after replacement

A new cell starts with higher internal impedance than a conditioned one. The charge IC pushes current into that resistance, and the conversion loss shows up as heat near the battery compartment. This is normal for the first one or two charge cycles and reduces as impedance drops. If warmth continues past the third full charge, check that the battery contacts are seated flat and making clean contact — poor contact forces the IC to compensate with higher voltage, which increases heat.