HB4F1 AT&T Impulse 4G Compatible Battery 3.7V 1500mAh

AT&T Impulse 4G — 3.7V Li-ion Replacement Battery (HB4F1)

This is a 3.7V, 1500mAh Li-ion cell built to replace the original HB4F1 battery in the AT&T Impulse 4G smartphone. It restores power for calls, messaging, and Android apps when the original cell no longer holds a usable charge. Voltage and capacity match OEM spec exactly — no modifications needed to the battery compartment or contacts.

• Impulse 4G battery platform: The HB4F1 uses a single-cell 3.7V nominal Li-ion architecture with a contact configuration specific to the Impulse 4G chassis. The BMS communicates cell state through those contacts — only cells with the correct pinout and voltage profile will initialise correctly with this device's charge IC.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on compatible hardware and confirmed the BMS handshake completes normally. The charge IC accepted the cell without error flags on the first cycle, and cutoff voltages held at expected thresholds throughout the test.
• Fuel gauge recalibration on first use: On first use after installation, run one full discharge down to auto-shutoff, then charge uninterrupted to 100%. This lets the fuel gauge IC map the new cell's discharge curve before it starts reporting percentages to the OS — skipping this step is the most common cause of erratic percentage readings.

Sudden shutdown at 20–30% on the Impulse 4G after a cell swap

This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell has a steeper voltage drop under modem and screen load than the aged cell the OS learned to read. When the phone pulls current for a 4G data burst or screen-on event, the cell voltage sags below the shutdown threshold before the reported percentage reaches zero. The fix is one full discharge-to-shutoff cycle followed by a full uninterrupted charge — after that, the coulomb counter resets its reference points to the new cell.

Phone won't power on after the replacement battery sat in storage

Li-ion cells self-discharge in storage, and if the HB4F1 cell dropped below approximately 2.5V per cell before installation, the BMS enters a lockout state to prevent damage. The phone will show no response — no charging indicator, no boot. Connect the phone to a wall charger (not a PC port) and leave it for 20–30 minutes without pressing the power button. The charge IC will trickle current into the cell to bring it above the BMS recovery threshold, typically around 2.9V, after which normal charging resumes and the phone will power on.