About this replacement
Samsung Galaxy A9 2018 — 3.85V Li-Polymer Replacement Battery (EB-BA920ABU)
This 3800mAh Li-Polymer cell replaces the original battery in the Samsung Galaxy A9 2018. It fits SM-A920F, SM-A920F/DS, and SM-A9200 variants. Voltage is 3.85V nominal, matching the charge IC and BMS parameters the device expects.
- SM-A920 variant coverage: The SM-A920F, SM-A920F/DS, and SM-A9200 all share the same battery bay dimensions, connector pinout, and BMS communication protocol — which is why a single cell covers the full A9 2018 lineup without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on SM-A920F hardware. The BMS handshake completed correctly, charge termination fired at 4.35V, and the protection circuit tripped cleanly at the low-voltage cutoff threshold.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard rate. This lets the fuel gauge IC build an accurate coulomb-counter baseline against the new cell's discharge curve before fast charging pushes higher current into an uncalibrated cell.
Sudden shutdown at 20–30% on the A9 2018 after a cell swap
The Galaxy A9 2018 runs a power-hungry combination of a large AMOLED panel and a modem that pulls hard current spikes during calls and data handoffs. When a new cell goes in, the fuel gauge IC is still calibrated to the old cell's internal resistance curve. At around 20–30% state-of-charge, the new cell's actual voltage under load drops faster than the IC predicts, crossing the hardware shutdown threshold before the percentage readout catches up. One complete discharge cycle — draining to auto-shutdown, then charging uninterrupted to 100% — recalibrates the coulomb counter and eliminates most of these premature cutoffs. If shutdowns persist past two full cycles, check resting voltage with a meter; it should sit above 3.7V at the 30% mark.
USB fast charge not activating on the first cycle after replacement
Samsung's Adaptive Fast Charging protocol requires the charge IC to negotiate with the battery BMS before stepping up to higher voltage. On the very first charge cycle with a new cell, some BMS firmware builds complete this negotiation on the second charge, not the first — so the phone charges slowly initially and the fast-charge indicator does not appear. This is not a fault with the charger or the cable. Disconnect after the first full charge, allow the phone to boot and settle for two minutes, then reconnect the original Samsung Adaptive Fast Charger. Fast charging should activate at that point and maintain on all subsequent cycles.