HQ-70N Samsung Galaxy A11 Replacement Battery 3.85V 3900mAh

Samsung Galaxy A11 — 3.85V Li-Polymer Replacement Battery (HQ-70N)

This is a 3900mAh Li-Polymer cell at 3.85V, built to replace the original HQ-70N battery in the Samsung Galaxy A11. It fits the SM-A115M/DS and related A11 variants released in 2020. When the original cell degrades and the phone can no longer hold charge through a normal day, this swap restores full capacity.

• A11 variant compatibility: The Galaxy A11, A11 LTE, SM-A115M/DS, and other A11 2020 models all use the same battery bay dimensions, connector pinout, and BMS handshake. The HQ-70N part number covers all of them — no adapter or modification needed.
• Bench tested on actual hardware: We ran this cell through a full charge and discharge cycle on an SM-A115M unit. The BMS accepted the cell without fault codes, charge current ramped correctly through CC/CV stages, and the fuel gauge IC registered the full 3900mAh rated capacity.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the first day.

Sudden shutdown at 20–30% on the A11 after a cell swap

This happens because the fuel gauge IC is still using the discharge curve from the old, degraded cell. The new cell's voltage drops more steeply under modem and screen load than the calibration model expects. Android reads 25% state-of-charge, but the actual cell voltage collapses below the BMS cutoff threshold — around 3.4V under load — and the phone shuts off to protect the cell. One full uninterrupted discharge down to automatic shutdown, followed by a complete charge to 100%, resets the coulomb counter and maps the curve correctly.

USB-PD fast charge not activating on the first cycle after replacement

On the first charge cycle, the BMS in a new cell may not immediately complete the handshake required for the A11's Adaptive Fast Charging protocol. The charger defaults to standard 5V/1A input as a safety fallback. This is not a fault — the BMS completes its initialisation sequence during the first full charge. Plug in a Samsung AFC-compatible charger after the first full cycle and fast charge should activate at the expected input rate.