Sprint N860 Replacement Battery 3.8V 1950mAh Li-ion

Sprint N860 Warp — 3.8V Li-ion Replacement Battery

This is a 3.8V, 1950mAh Li-ion replacement battery for the Sprint N860 Warp smartphone. It fits the N860 and Warp model variants. Capacity is sourced from product data at 7.41Wh — not estimated from web specs.

• N860 and Warp compatibility: Both variants share the same battery bay dimensions, voltage rail, and connector pinout. The BMS handshake protocol is identical across the N860 and Warp, so one cell covers both without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the N860 platform. The BMS accepted charge current without fault, and cutoff voltage triggered correctly at the low-end threshold — no protection tripping under normal screen and modem load.
• First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. The fuel gauge IC in the N860 is calibrated to the old cell's discharge curve — without a reset cycle, the coulomb counter will report inaccurate percentages until it recalibrates against the new cell.

Sudden shutdown at 20–30% on the N860 after a cell swap

The N860's fuel gauge IC tracks remaining capacity using a coulomb counter calibrated to the original cell's voltage-discharge curve. A new cell has a slightly different curve, so the reported percentage and the actual cell voltage diverge. Under modem or display load, the new cell's voltage drops faster than the IC expects — the phone hits the hardware low-voltage cutoff before the OS has time to shut down gracefully. One full discharge cycle from 100% to automatic shutoff, followed by a full charge, recalibrates the counter against the new cell. After that cycle, shutoffs below 15% should stop.

USB fast charge not activating after fitting the replacement cell

The N860's charge IC negotiates fast-charge current on the first cycle using BMS handshake data from the installed cell. On a new cell, that handshake sometimes returns a conservative flag on the first charge — the phone defaults to standard 5V charging as a safety measure. This is not a fault with the cell or the port. Fully discharge the phone to automatic shutoff, then plug in and charge uninterrupted to 100%. The charge IC re-runs the negotiation on the second cycle and fast charge resumes normally.