About this replacement
Samsung Galaxy S20 Plus — 3.85V Li-Polymer Replacement Battery (EB-BG985ABY)
This is a 3.85V, 4200mAh lithium-polymer replacement battery for the Samsung Galaxy S20 Plus. It fits SM-G985F, SM-G986B, SM-G986DS, SM-G986J, and additional SM-G986 variants. Part number EB-BG985ABY matches the original cell specification and connector layout.
- SM-G985 and SM-G986 compatibility: Both the standard S20 Plus and the 5G variant use the same battery bay dimensions and the same EB-BG985ABY connector pinout. The BMS handshake protocol is identical across these variants, so one cell covers both radio configurations.
- Bench tested on actual hardware: We ran this cell on an SM-G986B and monitored BMS behaviour through a full discharge and charge cycle. The protection IC responded correctly to cutoff at the low-voltage threshold and accepted Samsung's fast charge handshake without rejection flags on the second cycle.
- Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge down to auto-shutdown, then charge to 100% on standard power. This gives the fuel gauge IC a clean reference curve against the new cell before high-current charging pushes electrons into an uncalibrated counter.
Why the S20 Plus reports wrong battery percentage after a cell swap
The S20 Plus uses a coulomb counter inside the fuel gauge IC to track charge state. When you replace the physical cell, the IC still holds the discharge curve data from the old, degraded battery. The new cell has a steeper voltage curve at full charge and a different sag profile under load, so the counter reads incorrectly against those stored values. One full slow-charge discharge cycle forces the IC to remap its reference points to the new cell's actual behaviour.
Sudden shutdown at 15–25% on the replacement cell
This is a voltage cliff, not a capacity fault. Under combined modem and display load, the cell's output voltage drops sharply at lower states of charge — faster than the fuel gauge IC predicts. The phone's protection circuit cuts power before the percentage reaches zero because the voltage has already hit the minimum threshold. Run two full discharge-charge cycles without fast charging; by the third cycle the fuel gauge recalibration typically closes the gap and the cutoff moves back to the 3–5% range where it belongs.