Vodafone HB4J1 845 Replacement Battery 3.7V 1100mAh

Vodafone 845 / 858 Series — 3.7V Li-ion Replacement Battery (HB4J1)

This is a 3.7V, 1100mAh Li-ion cell for the Vodafone 845, 858, 858 Smart, and V858. It replaces the original HB4J1 / HB4J1H battery when the existing cell no longer holds a usable charge. The cell measures 54 × 43 × 5mm and slots directly into the rear-access battery bay.

• 845 and 858 platform compatibility: These models share the same battery footprint, connector pitch, and BMS handshake protocol. One cell covers the full range without any modification to the contacts or housing.
• Bench tested on actual hardware: We ran this cell on an 858 Smart unit. The BMS accepted the new cell without a reset loop, charge current stepped correctly through CC/CV phases, and the protection circuit tripped cleanly at the low-voltage cutoff threshold during discharge testing.
• Fuel gauge recalibration after swap: After fitting this cell, run one full discharge to shutdown followed by an uninterrupted charge to 100% before normal use. This gives the fuel gauge IC a complete discharge curve to map against the new cell — skipping this step is the main cause of erratic percentage readings post-swap.

Why the 845 and 858 report wrong battery percentage after a cell swap

The fuel gauge IC in these phones uses a coulomb counter that was calibrated to the discharge curve of the original cell. A new cell — even at the same rated capacity — presents a slightly different voltage-versus-charge profile. Until the IC runs one full cycle on the new cell, it interpolates percentage from stale reference data. The result is jumpy or frozen percentage readings that settle after the first complete discharge and recharge cycle.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem radio or display backlight draws a current spike the cell cannot sustain at low state-of-charge without voltage dropping below the BMS cutoff threshold. It is not a faulty cell — it is the fuel gauge reporting a higher percentage than the actual remaining capacity supports under load. Run the recalibration cycle described above. After a full discharge-recharge loop, the IC anchors its low-end estimate correctly and shutdowns below 3.4V under load should stop occurring.