Sprint ADMIRAL 3.7V Replacement Battery 1300mAh Li-ion

Sprint Admiral — 3.7V Li-ion Replacement Battery

This 3.7V, 1300mAh Li-ion battery replaces the original cell in the Sprint Admiral smartphone. It fits the Admiral's battery bay directly and restores power to calls, messaging, and apps. Capacity is 4.81Wh — matched to the original specification.

• Admiral battery bay fit: The Sprint Admiral uses a removable 3.7V single-cell Li-ion pack. This replacement matches the original cell's voltage rail and physical footprint at 49.95 × 45.50 × 5.70mm, so the rear cover seats flush without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS held cutoff at the correct low-voltage threshold and accepted charge current without tripping protection prematurely. Capacity output tracked within normal tolerance of the 1300mAh rating.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle before resuming normal use. The Admiral's fuel gauge IC is calibrated to the old cell's discharge curve — letting it complete one full cycle against the new cell gives it the data it needs to report accurate percentages.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff problem, not a capacity problem. Under modem load or screen-on draw, the new cell's terminal voltage drops faster than the fuel gauge IC expects — because the IC is still using the discharge curve it learned from the old, degraded cell. When voltage sags below the shutdown threshold, the phone cuts power even though the displayed percentage still reads 20–30%. One full discharge cycle — draining to automatic shutoff, then charging uninterrupted to 100% — lets the coulomb counter recalibrate against the new cell's actual curve. After that cycle, percentage readings stabilise and premature shutdowns stop.

Phone will not power on after the battery sat in storage

Li-ion cells self-discharge during storage. If a cell drops below approximately 2.5V, the BMS locks out to prevent damage and the phone will not respond to a normal power-on attempt. Connect the Admiral to its charger and leave it for 15–30 minutes without pressing the power button — the charger applies a trickle current that brings the cell back above the BMS re-enable threshold. Once the charge LED activates or the boot screen appears, the BMS has unlocked and normal charging can resume.