About this replacement
Apple iPhone 6s Plus — 3.8V Li-Polymer Replacement Battery (616-00042)
This 3.8V, 3000mAh (11.4Wh) lithium-polymer cell replaces the OEM battery in the iPhone 6s Plus, including models A1634, A1690, and A1699. It matches the original cell's dimensions at 119.00 × 47.65 × 4.00mm and uses the same connector and BMS handshake as the factory unit. Swap it in when the original cell can no longer hold charge through a normal day of use.
- 6s Plus platform fit: The A1634, A1690, and A1699 variants all share the same battery bay geometry, voltage rail, and BMS communication protocol. One cell covers the full 6s Plus lineup — no connector adapters or firmware workarounds needed.
- Bench tested on actual hardware: We cycled this cell in a 6s Plus unit and logged the BMS handshake across charge and discharge. The protection IC correctly flagged over-voltage at 4.35V and low-voltage cutoff activated before the cell dropped below the safe floor.
- Fuel gauge recalibration after installation: After fitting this cell, disable fast charging and run one full discharge-charge cycle at standard current. This lets the iPhone's fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins.
Sudden shutdown at 20–30% on the 6s Plus after a cell swap
This happens when the fuel gauge IC is still running a calibration curve built from the old, degraded cell. The new cell has a steeper voltage cliff under modem and display load than the iOS power manager expects. At high draw — LTE handoff, GPS burst, screen at full brightness — cell voltage drops momentarily below the shutdown threshold even though the reported percentage looks healthy. One full discharge to 1% and a complete charge to 100% at standard current resets the coulomb counter and eliminates most of these shutdowns.
iPhone 6s Plus showing incorrect battery percentage after replacement
The iOS fuel gauge IC does not automatically recalibrate when a new cell is installed — it carries over the learned curve from the previous battery. This mismatch causes percentage readings to jump, stall, or drop suddenly in the lower third of the charge range. Force a recalibration by draining the phone until it shuts down automatically, then charging uninterrupted to 100% without interruption. After one complete cycle, the coulomb counter anchors to the new cell's actual capacity and percentage reporting stabilises.