Apple iPhone 6s Replacement Battery 3.8V 1715mAh 616-00036

Apple iPhone 6s — 3.8V Li-Polymer Replacement Battery (616-00036)

This 3.8V, 1715mAh Li-Polymer cell replaces the original battery in the Apple iPhone 6s, covering model numbers A1633, A1688, and A1691. It matches the OEM part number 616-00036 and fits the same physical envelope at 96.00 × 38.14 × 3.40mm. Use this when the original cell degrades, causes unexpected shutdowns, or no longer holds a usable charge.

• A1633, A1688, A1691 fit confirmed: These three iPhone 6s variants share the same logic board connector, battery pocket dimensions, and BMS handshake protocol — one cell covers all three without modification.
• Bench tested on actual hardware: We cycled this cell through a full discharge and charge sequence on an iPhone 6s logic board. The BMS accepted the cell, reported voltage correctly, and thermal behaviour during the CC/CV charge transition stayed within normal range.
• Fuel gauge recalibration on first use: After installation, disable fast charging for one complete discharge-charge cycle. The iPhone's coulomb counter is calibrated to the old cell's discharge curve. Running one slow cycle first lets the fuel gauge IC map the new curve before fast charge current is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on a freshly installed cell

A new Li-Polymer cell has a slightly different internal resistance profile than the aged cell the iPhone's power management IC was tracking. Under high-current loads — active LTE, GPS, or screen at full brightness — voltage sags faster than the fuel gauge predicts. The iPhone's PMIC interprets the voltage drop as a critically low cell and cuts power before the percentage readout reaches zero. One full discharge-to-shutdown and uninterrupted charge cycle forces the coulomb counter to re-anchor its state-of-charge model to the new cell, and the early shutdowns typically stop.

iPhone 6s reporting wrong battery percentage after cell swap

The iPhone 6s stores learned discharge data in its fuel gauge IC tied to the previous cell's capacity and impedance. After swapping to a fresh 1715mAh cell, that stored model is stale, so percentage jumps erratically or reads lower than actual charge. This is not a defective battery — it is a calibration mismatch. Drain the phone fully until it powers off, then charge uninterrupted to 100% with the screen off. After one complete cycle, percentage reporting stabilises as the IC rebuilds its discharge curve against the new cell.