Hyundai A100 Replacement Battery BTR-4100 3.7V 1500mAh

Hyundai A100 — 3.7V Li-ion Replacement Battery (BTR-4100)

This is a 3.7V, 1500mAh Li-ion replacement battery for the Hyundai A100 smartphone. It replaces OEM part BTR-4100 and restores power to calling, messaging, and onboard applications. Fit the new cell when the original no longer holds a charge or the phone shuts down unexpectedly under load.

• Hyundai A100 fitment: The A100 uses a removable cell format with a three-pin connector that carries both power and BMS communication. The BTR-4100 cell matches that connector layout and voltage rail, so the phone's charge IC reads the new cell correctly without throwing a fault.
• Bench tested on actual hardware: We cycled this cell through a full charge-discharge run and confirmed the BMS handshake completed on first connection, charge current stepped down correctly at 4.2V, and the protection circuit tripped as expected at the low-voltage threshold.
• Fuel gauge recalibration on first use: After installation, disable fast charging if your A100 supports it and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the OS starts reporting percentage readings — skipping this step causes erratic percentage jumps in the first few days of use.

Sudden shutdown at 20–30% on the Hyundai A100

This is the most reported failure pattern on worn A100 cells and can persist briefly on a new cell until the fuel gauge recalibrates. The cell's actual voltage drops below the modem and screen's minimum supply threshold under load, even though the OS still reports 20–30% remaining. The fuel gauge IC is reading a state-of-charge curve that no longer matches the cell's real discharge profile. Run one full discharge to auto-off, then charge uninterrupted to 100%, and the shutdowns should stop after that first calibration cycle.

A100 not powering on after the replacement cell sat in storage

Li-ion cells self-discharge during storage, and if the BTR-4100 cell dropped below approximately 2.5V per cell while sitting in a warehouse, the BMS will have entered lockout mode to prevent further discharge damage. The phone will show no sign of life even on a charger at first. Connect to a charger and leave it for 20–30 minutes without pressing the power button — the charge IC needs time to trickle current into the cell and lift it above the BMS re-enable threshold, typically around 2.9V, before normal charging resumes.