First 1925-1 Compatible Battery 3.7V 1200mAh Li-ion 523450AR

First 1925-1 — 3.7V Li-ion Replacement Battery (523450AR 11-01)

This is a 3.7V, 1200mAh Li-ion cell for the First 1925-1 and FA-1925-1-BA smartphones. It replaces OEM part 523450AR 11-01 using the same voltage and connector configuration as the factory cell. Swap this in when the original battery no longer holds a charge or fails to power the device through normal use.

• 1925-1 and FA-1925-1-BA compatibility: Both model numbers share the same PCB connector, cell footprint, and 3.7V nominal voltage rail. The 523450AR 11-01 part number covers both variants, so no connector modification is needed on either unit.
• Bench tested on actual hardware: We cycled this cell through charge and load on the bench. The BMS held cutoff correctly at low voltage and accepted a standard charge current without tripping protection. Cell dimensions matched the 53.00 × 33.90 × 5.70mm bay on the 1925-1 chassis.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge-to-charge cycle before normal use. This lets the phone's fuel gauge IC map its coulomb counter against the new cell's actual discharge curve — skipping this step is the most common cause of erratic percentage readings.

Sudden shutdown at 20–30% on the First 1925-1 after a cell swap

The 1925-1 shuts off mid-use at 20–30% because the fuel gauge IC is still calibrated to the old cell's discharge curve. A fresh cell has a steeper voltage cliff at low charge states. When the modem or screen draws current, cell voltage drops quickly enough to trigger the low-voltage protection circuit before the OS reads zero. Running one full discharge and recharge cycle forces the coulomb counter to relearn the new cell and pushes the cutoff threshold back to the correct point.

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

A new cell arrives with higher internal impedance than a conditioned one. The charge IC pushes current into higher resistance on those first cycles, which generates more heat than you would see on a broken-in cell. This is normal and fades after two to three full cycles. If warmth continues beyond cycle three, check that the replacement cell sits flush in the bay — any lift can create a contact resistance point at the connector pins, and you should reseat the battery and confirm the connector latches at 3.7V open-circuit before charging again.