EA-BL21 Sharp SH7218C Compatible Battery 3.7V 850mAh

Sharp SH7218C / SH803T Series — 3.7V Li-ion Replacement Battery (EA-BL21)

This is a 3.7V, 850mAh Li-ion replacement battery for the Sharp SH7218C, SH7218U, SH803T, and SH806T mobile phones. It replaces OEM part EA-BL21 (also cross-referenced as O028A and 100700006007). Swap it in when the original cell can no longer hold a charge through a normal day of calls and messaging.

• SH7218C / SH803T platform fit: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers all four variants listed without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the SH7218C platform. The BMS accepted charge without fault flags, and voltage held within spec at both the modem load spike and screen-on draw peaks.
• Fuel gauge recalibration on first use: On first installation, disable fast charging and run one complete discharge-to-charge cycle before resuming normal use. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve — skipping this step causes the phone to report inaccurate percentages until it recalibrates on its own.

Sudden shutdown at 20–30% on a freshly installed cell

A new cell in the SH7218C can trigger abrupt shutdowns well above 0% because the fuel gauge IC still holds the discharge curve of the degraded original battery. When the modem ramps up during a call or the screen hits full brightness, current draw spikes and the new cell's voltage drops momentarily below the BMS cutoff threshold — even though capacity remains. The phone reads this as a dead battery and shuts down. Run one full discharge cycle without fast charging; the coulomb counter recalibrates, and the shutdowns stop. After recalibration, charge the phone to 100% before checking for further issues.

Phone feels warm near the battery compartment during the first few charges

A fresh Li-ion cell has slightly higher internal impedance than a broken-in cell, so the charge IC works harder to push current in during the first few cycles — generating more heat than you'd see with a well-cycled battery. This is normal and fades after two or three full charge cycles as the cell's impedance settles. If warmth continues past the third full charge or the phone becomes hot to the touch, check that the battery connector is fully seated and the bay cover is flush. Warmth that persists beyond cycle three at the same spot points to a connector seating issue, not the cell itself.